Messages in this thread | | | Date | Thu, 20 Oct 2016 20:16:06 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm, compaction: fix NR_ISOLATED_* stats for pfn based migration |
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On Wed, 19 Oct 2016 10:02:40 +0200 Michal Hocko <mhocko@kernel.org> wrote:
> Since bda807d44454 ("mm: migrate: support non-lru movable page > migration") isolate_migratepages_block) can isolate !PageLRU pages which > would acct_isolated account as NR_ISOLATED_*. Accounting these non-lru > pages NR_ISOLATED_{ANON,FILE} doesn't make any sense and it can misguide > heuristics based on those counters such as pgdat_reclaimable_pages resp. > too_many_isolated which would lead to unexpected stalls during the > direct reclaim without any good reason. Note that > __alloc_contig_migrate_range can isolate a lot of pages at once. > > On mobile devices such as 512M ram android Phone, it may use a big zram > swap. In some cases zram(zsmalloc) uses too many non-lru but migratedable > pages, such as: > > MemTotal: 468148 kB > Normal free:5620kB > Free swap:4736kB > Total swap:409596kB > ZRAM: 164616kB(zsmalloc non-lru pages) > active_anon:60700kB > inactive_anon:60744kB > active_file:34420kB > inactive_file:37532kB > > Fix this by only accounting lru pages to NR_ISOLATED_* in > isolate_migratepages_block right after they were isolated and we still > know they were on LRU. Drop acct_isolated because it is called after the > fact and we've lost that information. Batching per-cpu counter doesn't > make much improvement anyway. Also make sure that we uncharge only LRU > pages when putting them back on the LRU in putback_movable_pages resp. > when unmap_and_move migrates the page.
It isn't worth backporting into 4.8.x?
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