Re: [PATCH v2] mm/slub: don't wait for high-order page allocation
On Fri, 7 Aug 2015, Joonsoo Kim wrote:
> Almost description is copied from commit fb05e7a89f50
> ("net: don't wait for order-3 page allocation").
>
> I saw excessive direct memory reclaim/compaction triggered by slub.
> This causes performance issues and add latency. Slub uses high-order
> allocation to reduce internal fragmentation and management overhead. But,
> direct memory reclaim/compaction has high overhead and the benefit of
> high-order allocation can't compensate the overhead of both work.
>
> This patch makes auxiliary high-order allocation atomic. If there is
> no memory pressure and memory isn't fragmented, the alloction will still
> success, so we don't sacrifice high-order allocation's benefit here.
> If the atomic allocation fails, direct memory reclaim/compaction will not
> be triggered, allocation fallback to low-order immediately, hence
> the direct memory reclaim/compaction overhead is avoided. In the
> allocation failure case, kswapd is waken up and trying to make high-order
> freepages, so allocation could success next time.
>
> Following is the test to measure effect of this patch.
>
> System: QEMU, CPU 8, 512 MB
> Mem: 25% memory is allocated at random position to make fragmentation.
> Memory-hogger occupies 150 MB memory.
> Workload: hackbench -g 20 -l 1000
>
> Average result by 10 runs (Base va Patched)
>
> elapsed_time(s): 4.3468 vs 2.9838
> compact_stall: 461.7 vs 73.6
> pgmigrate_success: 28315.9 vs 7256.1
>
> Signed-off-by: Joonsoo Kim
Acked-by: David Rientjes
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Re: [PATCH v2] mm/slub: don't wait for high-order page allocation
On Fri, 7 Aug 2015, Joonsoo Kim wrote: Almost description is copied from commit fb05e7a89f50 (net: don't wait for order-3 page allocation). I saw excessive direct memory reclaim/compaction triggered by slub. This causes performance issues and add latency. Slub uses high-order allocation to reduce internal fragmentation and management overhead. But, direct memory reclaim/compaction has high overhead and the benefit of high-order allocation can't compensate the overhead of both work. This patch makes auxiliary high-order allocation atomic. If there is no memory pressure and memory isn't fragmented, the alloction will still success, so we don't sacrifice high-order allocation's benefit here. If the atomic allocation fails, direct memory reclaim/compaction will not be triggered, allocation fallback to low-order immediately, hence the direct memory reclaim/compaction overhead is avoided. In the allocation failure case, kswapd is waken up and trying to make high-order freepages, so allocation could success next time. Following is the test to measure effect of this patch. System: QEMU, CPU 8, 512 MB Mem: 25% memory is allocated at random position to make fragmentation. Memory-hogger occupies 150 MB memory. Workload: hackbench -g 20 -l 1000 Average result by 10 runs (Base va Patched) elapsed_time(s): 4.3468 vs 2.9838 compact_stall: 461.7 vs 73.6 pgmigrate_success: 28315.9 vs 7256.1 Signed-off-by: Joonsoo Kim iamjoonsoo@lge.com Acked-by: David Rientjes rient...@google.com -- 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 v2] mm/slub: don't wait for high-order page allocation
On Mon 10-08-15 09:40:22, Joonsoo Kim wrote: > On Fri, Aug 07, 2015 at 05:05:01PM +0200, Michal Hocko wrote: > > On Fri 07-08-15 11:10:03, Joonsoo Kim wrote: > > [...] > > > diff --git a/mm/slub.c b/mm/slub.c > > > index 257283f..52b9025 100644 > > > --- a/mm/slub.c > > > +++ b/mm/slub.c > > > @@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache > > > *s, gfp_t flags, int node) > > >* so we fall-back to the minimum order allocation. > > >*/ > > > alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL; > > > + if ((alloc_gfp & __GFP_WAIT) && oo_order(oo) > oo_order(s->min)) > > > + alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) & ~__GFP_WAIT; > > > > Wouldn't it be preferable to "fix" the __GFP_WAIT behavior than spilling > > __GFP_NOMEMALLOC around the kernel? GFP flags are getting harder and > > harder to use right and that is a signal we should thing about it and > > unclutter the current state. > > Maybe, it is preferable. Could you try that? I will try to cook up something during the week. > Anyway, it is separate issue so I don't want pending this patch until > that change. OK, fair enough, at least this one is in mm proper... -- Michal Hocko SUSE Labs -- 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 v2] mm/slub: don't wait for high-order page allocation
On Mon 10-08-15 09:40:22, Joonsoo Kim wrote: On Fri, Aug 07, 2015 at 05:05:01PM +0200, Michal Hocko wrote: On Fri 07-08-15 11:10:03, Joonsoo Kim wrote: [...] diff --git a/mm/slub.c b/mm/slub.c index 257283f..52b9025 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) * so we fall-back to the minimum order allocation. */ alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) ~__GFP_NOFAIL; + if ((alloc_gfp __GFP_WAIT) oo_order(oo) oo_order(s-min)) + alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) ~__GFP_WAIT; Wouldn't it be preferable to fix the __GFP_WAIT behavior than spilling __GFP_NOMEMALLOC around the kernel? GFP flags are getting harder and harder to use right and that is a signal we should thing about it and unclutter the current state. Maybe, it is preferable. Could you try that? I will try to cook up something during the week. Anyway, it is separate issue so I don't want pending this patch until that change. OK, fair enough, at least this one is in mm proper... -- Michal Hocko SUSE Labs -- 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 v2] mm/slub: don't wait for high-order page allocation
On Fri, Aug 07, 2015 at 05:05:01PM +0200, Michal Hocko wrote: > On Fri 07-08-15 11:10:03, Joonsoo Kim wrote: > [...] > > diff --git a/mm/slub.c b/mm/slub.c > > index 257283f..52b9025 100644 > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache > > *s, gfp_t flags, int node) > > * so we fall-back to the minimum order allocation. > > */ > > alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL; > > + if ((alloc_gfp & __GFP_WAIT) && oo_order(oo) > oo_order(s->min)) > > + alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) & ~__GFP_WAIT; > > Wouldn't it be preferable to "fix" the __GFP_WAIT behavior than spilling > __GFP_NOMEMALLOC around the kernel? GFP flags are getting harder and > harder to use right and that is a signal we should thing about it and > unclutter the current state. Maybe, it is preferable. Could you try that? Anyway, it is separate issue so I don't want pending this patch until that change. Thanks. -- 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 v2] mm/slub: don't wait for high-order page allocation
On Fri, Aug 07, 2015 at 05:05:01PM +0200, Michal Hocko wrote: On Fri 07-08-15 11:10:03, Joonsoo Kim wrote: [...] diff --git a/mm/slub.c b/mm/slub.c index 257283f..52b9025 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) * so we fall-back to the minimum order allocation. */ alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) ~__GFP_NOFAIL; + if ((alloc_gfp __GFP_WAIT) oo_order(oo) oo_order(s-min)) + alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) ~__GFP_WAIT; Wouldn't it be preferable to fix the __GFP_WAIT behavior than spilling __GFP_NOMEMALLOC around the kernel? GFP flags are getting harder and harder to use right and that is a signal we should thing about it and unclutter the current state. Maybe, it is preferable. Could you try that? Anyway, it is separate issue so I don't want pending this patch until that change. Thanks. -- 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 v2] mm/slub: don't wait for high-order page allocation
On Fri 07-08-15 11:10:03, Joonsoo Kim wrote:
[...]
> diff --git a/mm/slub.c b/mm/slub.c
> index 257283f..52b9025 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache *s,
> gfp_t flags, int node)
>* so we fall-back to the minimum order allocation.
>*/
> alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
> + if ((alloc_gfp & __GFP_WAIT) && oo_order(oo) > oo_order(s->min))
> + alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) & ~__GFP_WAIT;
Wouldn't it be preferable to "fix" the __GFP_WAIT behavior than spilling
__GFP_NOMEMALLOC around the kernel? GFP flags are getting harder and
harder to use right and that is a signal we should thing about it and
unclutter the current state.
>
> page = alloc_slab_page(s, alloc_gfp, node, oo);
> if (unlikely(!page)) {
> --
> 1.9.1
--
Michal Hocko
SUSE Labs
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Re: [PATCH v2] mm/slub: don't wait for high-order page allocation
On Fri 07-08-15 11:10:03, Joonsoo Kim wrote:
[...]
diff --git a/mm/slub.c b/mm/slub.c
index 257283f..52b9025 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache *s,
gfp_t flags, int node)
* so we fall-back to the minimum order allocation.
*/
alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) ~__GFP_NOFAIL;
+ if ((alloc_gfp __GFP_WAIT) oo_order(oo) oo_order(s-min))
+ alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) ~__GFP_WAIT;
Wouldn't it be preferable to fix the __GFP_WAIT behavior than spilling
__GFP_NOMEMALLOC around the kernel? GFP flags are getting harder and
harder to use right and that is a signal we should thing about it and
unclutter the current state.
page = alloc_slab_page(s, alloc_gfp, node, oo);
if (unlikely(!page)) {
--
1.9.1
--
Michal Hocko
SUSE Labs
--
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 v2] mm/slub: don't wait for high-order page allocation
Almost description is copied from commit fb05e7a89f50
("net: don't wait for order-3 page allocation").
I saw excessive direct memory reclaim/compaction triggered by slub.
This causes performance issues and add latency. Slub uses high-order
allocation to reduce internal fragmentation and management overhead. But,
direct memory reclaim/compaction has high overhead and the benefit of
high-order allocation can't compensate the overhead of both work.
This patch makes auxiliary high-order allocation atomic. If there is
no memory pressure and memory isn't fragmented, the alloction will still
success, so we don't sacrifice high-order allocation's benefit here.
If the atomic allocation fails, direct memory reclaim/compaction will not
be triggered, allocation fallback to low-order immediately, hence
the direct memory reclaim/compaction overhead is avoided. In the
allocation failure case, kswapd is waken up and trying to make high-order
freepages, so allocation could success next time.
Following is the test to measure effect of this patch.
System: QEMU, CPU 8, 512 MB
Mem: 25% memory is allocated at random position to make fragmentation.
Memory-hogger occupies 150 MB memory.
Workload: hackbench -g 20 -l 1000
Average result by 10 runs (Base va Patched)
elapsed_time(s): 4.3468 vs 2.9838
compact_stall: 461.7 vs 73.6
pgmigrate_success: 28315.9 vs 7256.1
Signed-off-by: Joonsoo Kim
---
mm/slub.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/slub.c b/mm/slub.c
index 257283f..52b9025 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache *s,
gfp_t flags, int node)
* so we fall-back to the minimum order allocation.
*/
alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
+ if ((alloc_gfp & __GFP_WAIT) && oo_order(oo) > oo_order(s->min))
+ alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) & ~__GFP_WAIT;
page = alloc_slab_page(s, alloc_gfp, node, oo);
if (unlikely(!page)) {
--
1.9.1
--
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/
[PATCH v2] mm/slub: don't wait for high-order page allocation
Almost description is copied from commit fb05e7a89f50
(net: don't wait for order-3 page allocation).
I saw excessive direct memory reclaim/compaction triggered by slub.
This causes performance issues and add latency. Slub uses high-order
allocation to reduce internal fragmentation and management overhead. But,
direct memory reclaim/compaction has high overhead and the benefit of
high-order allocation can't compensate the overhead of both work.
This patch makes auxiliary high-order allocation atomic. If there is
no memory pressure and memory isn't fragmented, the alloction will still
success, so we don't sacrifice high-order allocation's benefit here.
If the atomic allocation fails, direct memory reclaim/compaction will not
be triggered, allocation fallback to low-order immediately, hence
the direct memory reclaim/compaction overhead is avoided. In the
allocation failure case, kswapd is waken up and trying to make high-order
freepages, so allocation could success next time.
Following is the test to measure effect of this patch.
System: QEMU, CPU 8, 512 MB
Mem: 25% memory is allocated at random position to make fragmentation.
Memory-hogger occupies 150 MB memory.
Workload: hackbench -g 20 -l 1000
Average result by 10 runs (Base va Patched)
elapsed_time(s): 4.3468 vs 2.9838
compact_stall: 461.7 vs 73.6
pgmigrate_success: 28315.9 vs 7256.1
Signed-off-by: Joonsoo Kim iamjoonsoo@lge.com
---
mm/slub.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/slub.c b/mm/slub.c
index 257283f..52b9025 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1364,6 +1364,8 @@ static struct page *allocate_slab(struct kmem_cache *s,
gfp_t flags, int node)
* so we fall-back to the minimum order allocation.
*/
alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) ~__GFP_NOFAIL;
+ if ((alloc_gfp __GFP_WAIT) oo_order(oo) oo_order(s-min))
+ alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) ~__GFP_WAIT;
page = alloc_slab_page(s, alloc_gfp, node, oo);
if (unlikely(!page)) {
--
1.9.1
--
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/
