Re: [RFC][PATCH 00/12] mm: tweak page cache migration
On 10/7/20 8:52 AM, Yang Shi wrote: > On Wed, Oct 7, 2020 at 2:55 AM David Hildenbrand wrote: >> On 07.10.20 11:52, Michal Hocko wrote: >>> Am I the only one missing patch 1-5? lore.k.o doesn't seem to link them >>> under this message id either. >> I received no patches via linux-mm, only the cover letter and Dave's >> reply. (maybe some are still in flight ...) > Yes, exactly the same to me, but anyway I saw the patches via linux-kernel. > > And, it seems the github series doesn't reflect the changes made by this > series. Sorry about that. I'll try to resend the series. There have been some Intel->list troubles as of late, but I think I'm probably to blame for this one.
Re: [RFC][PATCH 00/12] mm: tweak page cache migration
On Wed, Oct 7, 2020 at 2:55 AM David Hildenbrand wrote: > > On 07.10.20 11:52, Michal Hocko wrote: > > Am I the only one missing patch 1-5? lore.k.o doesn't seem to link them > > under this message id either. > > I received no patches via linux-mm, only the cover letter and Dave's > reply. (maybe some are still in flight ...) Yes, exactly the same to me, but anyway I saw the patches via linux-kernel. And, it seems the github series doesn't reflect the changes made by this series. > > -- > Thanks, > > David / dhildenb > >
Re: [RFC][PATCH 00/12] mm: tweak page cache migration
On 07.10.20 11:52, Michal Hocko wrote: > Am I the only one missing patch 1-5? lore.k.o doesn't seem to link them > under this message id either. I received no patches via linux-mm, only the cover letter and Dave's reply. (maybe some are still in flight ...) -- Thanks, David / dhildenb
Re: [RFC][PATCH 00/12] mm: tweak page cache migration
Am I the only one missing patch 1-5? lore.k.o doesn't seem to link them under this message id either. On Tue 06-10-20 13:51:03, Dave Hansen wrote: > First of all, I think this little slice of code is a bit > under-documented. Perhaps this will help clarify things. > > I'm pretty confident the page_count() check in the first > patch is right, which is why I removed it outright. The > xas_load() check is a bit murkier, so I just left a > warning in for it. > > Cc: Nicholas Piggin > Cc: Andrew Morton > Cc: Matthew Wilcox (Oracle) > Cc: Yang Shi > Cc: linux...@kvack.org > Cc: linux-kernel@vger.kernel.org -- Michal Hocko SUSE Labs
Re: [RFC][PATCH 00/12] mm: tweak page cache migration
Ugh, sorry about that. I fat-fingered the wrong cover letter! This should have been Subject: [v4] Migrate Pages in lieu of discard -- Changes since (automigrate-20200818): * Fall back to normal reclaim when demotion fails The full series is also available here: https://github.com/hansendc/linux/tree/automigrate-20200818 I really just want folks to look at: [RFC][PATCH 08/12] mm/migrate: demote pages during reclaim I've reworked that so that it can both use the high-level migration API, and fall back to normal reclaim if migration fails. I think that gives us the best of both worlds. I'm posting the series in case folks want to run the whole thing. -- We're starting to see systems with more and more kinds of memory such as Intel's implementation of persistent memory. Let's say you have a system with some DRAM and some persistent memory. Today, once DRAM fills up, reclaim will start and some of the DRAM contents will be thrown out. Allocations will, at some point, start falling over to the slower persistent memory. That has two nasty properties. First, the newer allocations can end up in the slower persistent memory. Second, reclaimed data in DRAM are just discarded even if there are gobs of space in persistent memory that could be used. This set implements a solution to these problems. At the end of the reclaim process in shrink_page_list() just before the last page refcount is dropped, the page is migrated to persistent memory instead of being dropped. While I've talked about a DRAM/PMEM pairing, this approach would function in any environment where memory tiers exist. This is not perfect. It "strands" pages in slower memory and never brings them back to fast DRAM. Other things need to be built to promote hot pages back to DRAM. == Open Issues == * For cpusets and memory policies that restrict allocations to PMEM, is it OK to demote to PMEM? Do we need a cgroup- level API to opt-in or opt-out of these migrations? Cc: Yang Shi Cc: David Rientjes Cc: Huang Ying Cc: Dan Williams -- Changes since (https://lwn.net/Articles/824830/): * Use higher-level migrate_pages() API approach from Yang Shi's earlier patches. * made sure to actually check node_reclaim_mode's new bit * disabled migration entirely before introducing RECLAIM_MIGRATE * Replace GFP_NOWAIT with explicit __GFP_KSWAPD_RECLAIM and comment why we want that. * Comment on effects of that keep multiple source nodes from sharing target nodes
[RFC][PATCH 00/12] mm: tweak page cache migration
First of all, I think this little slice of code is a bit under-documented. Perhaps this will help clarify things. I'm pretty confident the page_count() check in the first patch is right, which is why I removed it outright. The xas_load() check is a bit murkier, so I just left a warning in for it. Cc: Nicholas Piggin Cc: Andrew Morton Cc: Matthew Wilcox (Oracle) Cc: Yang Shi Cc: linux...@kvack.org Cc: linux-kernel@vger.kernel.org
