[PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On 2012-8-22 16:37, Minchan Kim wrote: > Hi Jiang, > > On Wed, Aug 22, 2012 at 04:30:09PM +0800, Jiang Liu wrote: >> On 2012-8-22 16:14, Minchan Kim wrote: >>> On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: On 2012-8-22 11:34, Minchan Kim wrote: > Hello Xishi, > > On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: >> From: Xishi Qiu >> >> When offline a section, we move all the free pages and pcp into >> MIGRATE_ISOLATE list first. >> start_isolate_page_range() >> set_migratetype_isolate() >> drain_all_pages(), >> >> Here is a problem, it is not sure that pcp will be moved into >> MIGRATE_ISOLATE list. They may >> be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So >> when finish migrating >> pages, the free pages from pcp may be allocated again, and faild in >> check_pages_isolated(). >> drain_all_pages() >> drain_local_pages() >> drain_pages() >> free_pcppages_bulk() >> __free_one_page(page, zone, 0, >> page_private(page)); >> >> If we add move_freepages_block() after drain_all_pages(), it can not >> sure that all the pcp >> will be moved into MIGRATE_ISOLATE list when the system works on high >> load. The free pages >> which from pcp may immediately be allocated again. >> >> I think the similar bug described in >> http://marc.info/?t=13425088233=1=2 > > Yes. I reported the problem a few month ago but it's not real bug in > practice > but found by my eyes during looking the code so I wanted to confirm the > problem. > > Do you find that problem in real practice? or just code review? > I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. > Anyway, I don't like your approach which I already considered because it > hurts hotpath > while the race is really unlikely. Get_pageblock_migratetype is never > trivial. > We should avoid the overhead in hotpath and move into memory-hotplug > itself. > Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? >>> >>> Allocator doesn't have any lock when he allocates the page from pcp. >>> How could you prevent race between allocator and memory-hotplug >>> routine(ie, set_migratetype_isolate) without hurting hotpath? >> Hi Minchan, >> I have thought about using a jump label in the hot path, which won't >> cause big >> performance drop, but it seems a little dirty. What's your thoughts? > > I don't know static_key_false internal well. > Questions. > > 1. Is it implemented by all archs? > 2. How is it work? It's almost zero on all archs? > 3. Don't we really have any solution other than hacking the hotpath >(ie, order-0 page allocation)? > 4. Please see my solution on above URL. Does it has any problem? > Hi Minchan, Yes, your patch does resolve this problem, it returns the failed flag in __test_page_isolated_in_pageblock(), so memory offline will be failed. My patch resolve this problem too, it drain pcp to MIGRATE_ISOLATE list, so memory offline will be successful, but it causes big performance drop. I think Gerry's method looks fine. Thanks Xishi Qiu >> >> migrate_type = page_private(page); >> if (static_key_false(_hotplug_inprogress)) >> migrate_type = get_pageblock_migratetype(page); >> __free_one_page(page, zone, 0, migrate_type); >> >> Regards! >> Gerry >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majord...@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: mailto:"d...@kvack.org;> em...@kvack.org > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On 2012-8-22 16:37, Minchan Kim wrote: Hi Jiang, On Wed, Aug 22, 2012 at 04:30:09PM +0800, Jiang Liu wrote: On 2012-8-22 16:14, Minchan Kim wrote: On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: On 2012-8-22 11:34, Minchan Kim wrote: Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? Allocator doesn't have any lock when he allocates the page from pcp. How could you prevent race between allocator and memory-hotplug routine(ie, set_migratetype_isolate) without hurting hotpath? Hi Minchan, I have thought about using a jump label in the hot path, which won't cause big performance drop, but it seems a little dirty. What's your thoughts? I don't know static_key_false internal well. Questions. 1. Is it implemented by all archs? 2. How is it work? It's almost zero on all archs? 3. Don't we really have any solution other than hacking the hotpath (ie, order-0 page allocation)? 4. Please see my solution on above URL. Does it has any problem? Hi Minchan, Yes, your patch does resolve this problem, it returns the failed flag in __test_page_isolated_in_pageblock(), so memory offline will be failed. My patch resolve this problem too, it drain pcp to MIGRATE_ISOLATE list, so memory offline will be successful, but it causes big performance drop. I think Gerry's method looks fine. Thanks Xishi Qiu migrate_type = page_private(page); if (static_key_false(memory_hotplug_inprogress)) migrate_type = get_pageblock_migratetype(page); __free_one_page(page, zone, 0, migrate_type); Regards! Gerry -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majord...@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: a href=mailto:d...@kvack.org; em...@kvack.org /a -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
Hi Jiang, On Wed, Aug 22, 2012 at 04:30:09PM +0800, Jiang Liu wrote: > On 2012-8-22 16:14, Minchan Kim wrote: > > On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: > >> On 2012-8-22 11:34, Minchan Kim wrote: > >>> Hello Xishi, > >>> > >>> On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: > From: Xishi Qiu > > When offline a section, we move all the free pages and pcp into > MIGRATE_ISOLATE list first. > start_isolate_page_range() > set_migratetype_isolate() > drain_all_pages(), > > Here is a problem, it is not sure that pcp will be moved into > MIGRATE_ISOLATE list. They may > be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So > when finish migrating > pages, the free pages from pcp may be allocated again, and faild in > check_pages_isolated(). > drain_all_pages() > drain_local_pages() > drain_pages() > free_pcppages_bulk() > __free_one_page(page, zone, 0, > page_private(page)); > > If we add move_freepages_block() after drain_all_pages(), it can not > sure that all the pcp > will be moved into MIGRATE_ISOLATE list when the system works on high > load. The free pages > which from pcp may immediately be allocated again. > > I think the similar bug described in > http://marc.info/?t=13425088233=1=2 > >>> > >>> Yes. I reported the problem a few month ago but it's not real bug in > >>> practice > >>> but found by my eyes during looking the code so I wanted to confirm the > >>> problem. > >>> > >>> Do you find that problem in real practice? or just code review? > >>> > >> > >> I use /sys/devices/system/memory/soft_offline_page to offline a lot of > >> pages when the > >> system works on high load, then I find some unknown zero refcount pages, > >> such as > >> get_any_page: 0x650422: unknown zero refcount page type 19400c > >> get_any_page: 0x650867: unknown zero refcount page type 19400c > >> > >> soft_offline_page() > >>get_any_page() > >>set_migratetype_isolate() > >>drain_all_pages() > >> > >> I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list > >> which managed by > >> buddy allocator, but they are allocated and becaome pcp again as the > >> system works on high > >> load. There will be no this problem by applying this patch. > >> > >>> Anyway, I don't like your approach which I already considered because it > >>> hurts hotpath > >>> while the race is really unlikely. Get_pageblock_migratetype is never > >>> trivial. > >>> We should avoid the overhead in hotpath and move into memory-hotplug > >>> itself. > >>> Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? > >> > >> Yes, you are right, I will try to find another way to fix this problem. > >> How about doing this work in set_migratetype_isolate(), find the pcp and > >> change the value > >> of private to get_pageblock_migratetype(page)? > >> > > > > Allocator doesn't have any lock when he allocates the page from pcp. > > How could you prevent race between allocator and memory-hotplug > > routine(ie, set_migratetype_isolate) without hurting hotpath? > Hi Minchan, > I have thought about using a jump label in the hot path, which won't > cause big > performance drop, but it seems a little dirty. What's your thoughts? I don't know static_key_false internal well. Questions. 1. Is it implemented by all archs? 2. How is it work? It's almost zero on all archs? 3. Don't we really have any solution other than hacking the hotpath (ie, order-0 page allocation)? 4. Please see my solution on above URL. Does it has any problem? > > migrate_type = page_private(page); > if (static_key_false(_hotplug_inprogress)) > migrate_type = get_pageblock_migratetype(page); > __free_one_page(page, zone, 0, migrate_type); > > Regards! > Gerry > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majord...@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: mailto:"d...@kvack.org;> em...@kvack.org -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On 2012-8-22 16:14, Minchan Kim wrote: > On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: >> On 2012-8-22 11:34, Minchan Kim wrote: >>> Hello Xishi, >>> >>> On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233=1=2 >>> >>> Yes. I reported the problem a few month ago but it's not real bug in >>> practice >>> but found by my eyes during looking the code so I wanted to confirm the >>> problem. >>> >>> Do you find that problem in real practice? or just code review? >>> >> >> I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages >> when the >> system works on high load, then I find some unknown zero refcount pages, >> such as >> get_any_page: 0x650422: unknown zero refcount page type 19400c >> get_any_page: 0x650867: unknown zero refcount page type 19400c >> >> soft_offline_page() >> get_any_page() >> set_migratetype_isolate() >> drain_all_pages() >> >> I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list >> which managed by >> buddy allocator, but they are allocated and becaome pcp again as the system >> works on high >> load. There will be no this problem by applying this patch. >> >>> Anyway, I don't like your approach which I already considered because it >>> hurts hotpath >>> while the race is really unlikely. Get_pageblock_migratetype is never >>> trivial. >>> We should avoid the overhead in hotpath and move into memory-hotplug itself. >>> Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? >> >> Yes, you are right, I will try to find another way to fix this problem. >> How about doing this work in set_migratetype_isolate(), find the pcp and >> change the value >> of private to get_pageblock_migratetype(page)? >> > > Allocator doesn't have any lock when he allocates the page from pcp. > How could you prevent race between allocator and memory-hotplug > routine(ie, set_migratetype_isolate) without hurting hotpath? Hi Minchan, I have thought about using a jump label in the hot path, which won't cause big performance drop, but it seems a little dirty. What's your thoughts? migrate_type = page_private(page); if (static_key_false(_hotplug_inprogress)) migrate_type = get_pageblock_migratetype(page); __free_one_page(page, zone, 0, migrate_type); Regards! Gerry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: > On 2012-8-22 11:34, Minchan Kim wrote: > > Hello Xishi, > > > > On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: > >> From: Xishi Qiu > >> > >> When offline a section, we move all the free pages and pcp into > >> MIGRATE_ISOLATE list first. > >> start_isolate_page_range() > >>set_migratetype_isolate() > >>drain_all_pages(), > >> > >> Here is a problem, it is not sure that pcp will be moved into > >> MIGRATE_ISOLATE list. They may > >> be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when > >> finish migrating > >> pages, the free pages from pcp may be allocated again, and faild in > >> check_pages_isolated(). > >> drain_all_pages() > >>drain_local_pages() > >>drain_pages() > >>free_pcppages_bulk() > >>__free_one_page(page, zone, 0, > >> page_private(page)); > >> > >> If we add move_freepages_block() after drain_all_pages(), it can not sure > >> that all the pcp > >> will be moved into MIGRATE_ISOLATE list when the system works on high > >> load. The free pages > >> which from pcp may immediately be allocated again. > >> > >> I think the similar bug described in > >> http://marc.info/?t=13425088233=1=2 > > > > Yes. I reported the problem a few month ago but it's not real bug in > > practice > > but found by my eyes during looking the code so I wanted to confirm the > > problem. > > > > Do you find that problem in real practice? or just code review? > > > > I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages > when the > system works on high load, then I find some unknown zero refcount pages, such > as > get_any_page: 0x650422: unknown zero refcount page type 19400c > get_any_page: 0x650867: unknown zero refcount page type 19400c > > soft_offline_page() > get_any_page() > set_migratetype_isolate() > drain_all_pages() > > I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list > which managed by > buddy allocator, but they are allocated and becaome pcp again as the system > works on high > load. There will be no this problem by applying this patch. > > > Anyway, I don't like your approach which I already considered because it > > hurts hotpath > > while the race is really unlikely. Get_pageblock_migratetype is never > > trivial. > > We should avoid the overhead in hotpath and move into memory-hotplug itself. > > Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? > > Yes, you are right, I will try to find another way to fix this problem. > How about doing this work in set_migratetype_isolate(), find the pcp and > change the value > of private to get_pageblock_migratetype(page)? > Allocator doesn't have any lock when he allocates the page from pcp. How could you prevent race between allocator and memory-hotplug routine(ie, set_migratetype_isolate) without hurting hotpath? -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On 2012-8-22 11:34, Minchan Kim wrote: > Hello Xishi, > > On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: >> From: Xishi Qiu >> >> When offline a section, we move all the free pages and pcp into >> MIGRATE_ISOLATE list first. >> start_isolate_page_range() >> set_migratetype_isolate() >> drain_all_pages(), >> >> Here is a problem, it is not sure that pcp will be moved into >> MIGRATE_ISOLATE list. They may >> be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when >> finish migrating >> pages, the free pages from pcp may be allocated again, and faild in >> check_pages_isolated(). >> drain_all_pages() >> drain_local_pages() >> drain_pages() >> free_pcppages_bulk() >> __free_one_page(page, zone, 0, >> page_private(page)); >> >> If we add move_freepages_block() after drain_all_pages(), it can not sure >> that all the pcp >> will be moved into MIGRATE_ISOLATE list when the system works on high load. >> The free pages >> which from pcp may immediately be allocated again. >> >> I think the similar bug described in >> http://marc.info/?t=13425088233=1=2 > > Yes. I reported the problem a few month ago but it's not real bug in practice > but found by my eyes during looking the code so I wanted to confirm the > problem. > > Do you find that problem in real practice? or just code review? > I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. > Anyway, I don't like your approach which I already considered because it > hurts hotpath > while the race is really unlikely. Get_pageblock_migratetype is never trivial. > We should avoid the overhead in hotpath and move into memory-hotplug itself. > Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? Thanks Xishi Qiu >> >> >> Signed-off-by: Xishi Qiu >> --- >> mm/page_alloc.c |3 ++- >> 1 files changed, 2 insertions(+), 1 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index d0723b2..501f6de 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int >> count, >> /* must delete as __free_one_page list manipulates */ >> list_del(>lru); >> /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ >> -__free_one_page(page, zone, 0, page_private(page)); >> +__free_one_page(page, zone, 0, >> +get_pageblock_migratetype(page)); >> trace_mm_page_pcpu_drain(page, 0, page_private(page)); >> } while (--to_free && --batch_free && !list_empty(list)); >> } >> -- 1.7.6.1 . >> >> >> >> . >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majord...@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: mailto:"d...@kvack.org;> em...@kvack.org > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On 2012-8-22 11:34, Minchan Kim wrote: Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? Thanks Xishi Qiu Signed-off-by: Xishi Qiu qiuxi...@huawei.com --- mm/page_alloc.c |3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d0723b2..501f6de 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int count, /* must delete as __free_one_page list manipulates */ list_del(page-lru); /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ -__free_one_page(page, zone, 0, page_private(page)); +__free_one_page(page, zone, 0, +get_pageblock_migratetype(page)); trace_mm_page_pcpu_drain(page, 0, page_private(page)); } while (--to_free --batch_free !list_empty(list)); } -- 1.7.6.1 . . -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majord...@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: a href=mailto:d...@kvack.org; em...@kvack.org /a -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: On 2012-8-22 11:34, Minchan Kim wrote: Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? Allocator doesn't have any lock when he allocates the page from pcp. How could you prevent race between allocator and memory-hotplug routine(ie, set_migratetype_isolate) without hurting hotpath? -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
On 2012-8-22 16:14, Minchan Kim wrote: On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: On 2012-8-22 11:34, Minchan Kim wrote: Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? Allocator doesn't have any lock when he allocates the page from pcp. How could you prevent race between allocator and memory-hotplug routine(ie, set_migratetype_isolate) without hurting hotpath? Hi Minchan, I have thought about using a jump label in the hot path, which won't cause big performance drop, but it seems a little dirty. What's your thoughts? migrate_type = page_private(page); if (static_key_false(memory_hotplug_inprogress)) migrate_type = get_pageblock_migratetype(page); __free_one_page(page, zone, 0, migrate_type); Regards! Gerry -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
Hi Jiang, On Wed, Aug 22, 2012 at 04:30:09PM +0800, Jiang Liu wrote: On 2012-8-22 16:14, Minchan Kim wrote: On Wed, Aug 22, 2012 at 03:57:45PM +0800, qiuxishi wrote: On 2012-8-22 11:34, Minchan Kim wrote: Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? I use /sys/devices/system/memory/soft_offline_page to offline a lot of pages when the system works on high load, then I find some unknown zero refcount pages, such as get_any_page: 0x650422: unknown zero refcount page type 19400c get_any_page: 0x650867: unknown zero refcount page type 19400c soft_offline_page() get_any_page() set_migratetype_isolate() drain_all_pages() I think after drain_all_pages(), pcp are moved into MIGRATE_MOVABLE list which managed by buddy allocator, but they are allocated and becaome pcp again as the system works on high load. There will be no this problem by applying this patch. Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Yes, you are right, I will try to find another way to fix this problem. How about doing this work in set_migratetype_isolate(), find the pcp and change the value of private to get_pageblock_migratetype(page)? Allocator doesn't have any lock when he allocates the page from pcp. How could you prevent race between allocator and memory-hotplug routine(ie, set_migratetype_isolate) without hurting hotpath? Hi Minchan, I have thought about using a jump label in the hot path, which won't cause big performance drop, but it seems a little dirty. What's your thoughts? I don't know static_key_false internal well. Questions. 1. Is it implemented by all archs? 2. How is it work? It's almost zero on all archs? 3. Don't we really have any solution other than hacking the hotpath (ie, order-0 page allocation)? 4. Please see my solution on above URL. Does it has any problem? migrate_type = page_private(page); if (static_key_false(memory_hotplug_inprogress)) migrate_type = get_pageblock_migratetype(page); __free_one_page(page, zone, 0, migrate_type); Regards! Gerry -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majord...@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: a href=mailto:d...@kvack.org; em...@kvack.org /a -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: > From: Xishi Qiu > > When offline a section, we move all the free pages and pcp into > MIGRATE_ISOLATE list first. > start_isolate_page_range() > set_migratetype_isolate() > drain_all_pages(), > > Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE > list. They may > be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when > finish migrating > pages, the free pages from pcp may be allocated again, and faild in > check_pages_isolated(). > drain_all_pages() > drain_local_pages() > drain_pages() > free_pcppages_bulk() > __free_one_page(page, zone, 0, > page_private(page)); > > If we add move_freepages_block() after drain_all_pages(), it can not sure > that all the pcp > will be moved into MIGRATE_ISOLATE list when the system works on high load. > The free pages > which from pcp may immediately be allocated again. > > I think the similar bug described in > http://marc.info/?t=13425088233=1=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? > > > Signed-off-by: Xishi Qiu > --- > mm/page_alloc.c |3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index d0723b2..501f6de 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int > count, > /* must delete as __free_one_page list manipulates */ > list_del(>lru); > /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ > - __free_one_page(page, zone, 0, page_private(page)); > + __free_one_page(page, zone, 0, > + get_pageblock_migratetype(page)); > trace_mm_page_pcpu_drain(page, 0, page_private(page)); > } while (--to_free && --batch_free && !list_empty(list)); > } > -- 1.7.6.1 . > > > > . > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majord...@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: mailto:"d...@kvack.org;> em...@kvack.org -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] memory-hotplug: fix a drain pcp bug when offline pages
From: Xishi Qiu When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233=1=2 Signed-off-by: Xishi Qiu --- mm/page_alloc.c |3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d0723b2..501f6de 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int count, /* must delete as __free_one_page list manipulates */ list_del(>lru); /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ - __free_one_page(page, zone, 0, page_private(page)); + __free_one_page(page, zone, 0, + get_pageblock_migratetype(page)); trace_mm_page_pcpu_drain(page, 0, page_private(page)); } while (--to_free && --batch_free && !list_empty(list)); } -- 1.7.6.1 . . -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] memory-hotplug: fix a drain pcp bug when offline pages
Hello Xishi, On Tue, Aug 21, 2012 at 08:12:05PM +0800, qiuxishi wrote: From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Yes. I reported the problem a few month ago but it's not real bug in practice but found by my eyes during looking the code so I wanted to confirm the problem. Do you find that problem in real practice? or just code review? Anyway, I don't like your approach which I already considered because it hurts hotpath while the race is really unlikely. Get_pageblock_migratetype is never trivial. We should avoid the overhead in hotpath and move into memory-hotplug itself. Do you see my patch in https://patchwork.kernel.org/patch/1225081/ ? Signed-off-by: Xishi Qiu qiuxi...@huawei.com --- mm/page_alloc.c |3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d0723b2..501f6de 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int count, /* must delete as __free_one_page list manipulates */ list_del(page-lru); /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ - __free_one_page(page, zone, 0, page_private(page)); + __free_one_page(page, zone, 0, + get_pageblock_migratetype(page)); trace_mm_page_pcpu_drain(page, 0, page_private(page)); } while (--to_free --batch_free !list_empty(list)); } -- 1.7.6.1 . . -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majord...@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: a href=mailto:d...@kvack.org; em...@kvack.org /a -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] memory-hotplug: fix a drain pcp bug when offline pages
From: Xishi Qiu qiuxi...@huawei.com When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first. start_isolate_page_range() set_migratetype_isolate() drain_all_pages(), Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated(). drain_all_pages() drain_local_pages() drain_pages() free_pcppages_bulk() __free_one_page(page, zone, 0, page_private(page)); If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages which from pcp may immediately be allocated again. I think the similar bug described in http://marc.info/?t=13425088233r=1w=2 Signed-off-by: Xishi Qiu qiuxi...@huawei.com --- mm/page_alloc.c |3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d0723b2..501f6de 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int count, /* must delete as __free_one_page list manipulates */ list_del(page-lru); /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */ - __free_one_page(page, zone, 0, page_private(page)); + __free_one_page(page, zone, 0, + get_pageblock_migratetype(page)); trace_mm_page_pcpu_drain(page, 0, page_private(page)); } while (--to_free --batch_free !list_empty(list)); } -- 1.7.6.1 . . -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
