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Mon, 6 Nov 2023 14:46:04 +0800 From: Liu Shixin To: Andrew Morton , Yosry Ahmed , Huang Ying , Sachin Sant , Michal Hocko , Johannes Weiner , Kefeng Wang CC: , , Liu Shixin Subject: [PATCH v8] mm: vmscan: try to reclaim swapcache pages if no swap space Date: Mon, 6 Nov 2023 15:44:52 +0800 Message-ID: <20231106074452.2581835-1-liushixin2@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.175.113.32] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemd200004.china.huawei.com (7.185.36.141) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: D6C8C40010 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: jsnp4dbuaut5w36pt5tn917d6cnp5q6e X-HE-Tag: 1699253168-646929 X-HE-Meta: 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 ShCMXAue /DVFRire3jgrNm7tQCHOHWwfRvGTrH7GcEjVcaoFb97f+0oBl/AFUE8gK3xLhVz63FgVXfHnzS+xgC1Va8z91q9cV+hKbpEuHe3n4fzzo4aWTs+q3o/sbW2s6wc+hGWWLhlvhpnoJsZ+rQWPEB7fWiHr9Mrl2BP5qz7jwwWujWvbtyIZZeHrI4gKvv/TmjtEd5M00K7PAKCG7vfmaCEPKPe05mwnJjnyLheakQxNNscy97minh2AtERnF78wJBZBEyyxnPIYKVkm9iFV+VOatj8Mykg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When spaces of swap devices are exhausted, only file pages can be reclaimed. But there are still some swapcache pages in anon lru list. This can lead to a premature out-of-memory. The problem is found with such step: Firstly, set a 9MB disk swap space, then create a cgroup with 10MB memory limit, then runs an program to allocates about 15MB memory. The problem occurs occasionally, which may need about 100 times [1]. Fix it by checking number of swapcache pages in can_reclaim_anon_pages(). If the number is not zero, return true and set swapcache_only to 1. When scan anon lru list in swapcache_only mode, non-swapcache pages will be skipped to isolate in order to accelerate reclaim efficiency. However, in swapcache_only mode, the scan count still increased when scan non-swapcache pages because there are large number of non-swapcache pages and rare swapcache pages in swapcache_only mode, and if the non-swapcache is skipped and do not count, the scan of pages in isolate_lru_folios() can eventually lead to hung task, just as Sachin reported [2]. By the way, since there are enough times of memory reclaim before OOM, it is not need to isolate too much swapcache pages in one times. [1]. https://lore.kernel.org/lkml/CAJD7tkZAfgncV+KbKr36=eDzMnT=9dZOT0dpMWcurHLr6Do+GA@mail.gmail.com/ [2]. https://lore.kernel.org/linux-mm/CAJD7tkafz_2XAuqE8tGLPEcpLngewhUo=5US14PAtSM9tLBUQg@mail.gmail.com/ Signed-off-by: Liu Shixin Tested-by: Yosry Ahmed Reviewed-by: "Huang, Ying" Reviewed-by: Yosry Ahmed --- v7->v8: Reset swapcache_only at the beginning of can_reclaim_anon_pages(). v6->v7: Reset swapcache_only to zero after there are swap spaces. v5->v6: Fix NULL pointing derefence and hung task problem reported by Sachin. include/linux/swap.h | 6 ++++++ mm/memcontrol.c | 8 ++++++++ mm/vmscan.c | 27 +++++++++++++++++++++++++++ 3 files changed, 41 insertions(+) diff --git a/include/linux/swap.h b/include/linux/swap.h index f6dd6575b905..3ba146ae7cf5 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -659,6 +659,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p } extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg); +extern long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg); extern bool mem_cgroup_swap_full(struct folio *folio); #else static inline void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry) @@ -681,6 +682,11 @@ static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg) return get_nr_swap_pages(); } +static inline long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg) +{ + return total_swapcache_pages(); +} + static inline bool mem_cgroup_swap_full(struct folio *folio) { return vm_swap_full(); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 5b009b233ab8..29e34c06ca83 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7584,6 +7584,14 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg) return nr_swap_pages; } +long mem_cgroup_get_nr_swapcache_pages(struct mem_cgroup *memcg) +{ + if (mem_cgroup_disabled()) + return total_swapcache_pages(); + + return memcg_page_state(memcg, NR_SWAPCACHE); +} + bool mem_cgroup_swap_full(struct folio *folio) { struct mem_cgroup *memcg; diff --git a/mm/vmscan.c b/mm/vmscan.c index 6f13394b112e..5d5a169ec98c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -137,6 +137,9 @@ struct scan_control { /* Always discard instead of demoting to lower tier memory */ unsigned int no_demotion:1; + /* Swap space is exhausted, only reclaim swapcache for anon LRU */ + unsigned int swapcache_only:1; + /* Allocation order */ s8 order; @@ -606,6 +609,9 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, int nid, struct scan_control *sc) { + if (sc) + sc->swapcache_only = 0; + if (memcg == NULL) { /* * For non-memcg reclaim, is there @@ -613,10 +619,22 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, */ if (get_nr_swap_pages() > 0) return true; + /* Is there any swapcache pages to reclaim? */ + if (total_swapcache_pages() > 0) { + if (sc) + sc->swapcache_only = 1; + return true; + } } else { /* Is the memcg below its swap limit? */ if (mem_cgroup_get_nr_swap_pages(memcg) > 0) return true; + /* Is there any swapcache pages in memcg to reclaim? */ + if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) { + if (sc) + sc->swapcache_only = 1; + return true; + } } /* @@ -2342,6 +2360,15 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan, */ scan += nr_pages; + /* + * Count non-swapcache too because the swapcache pages may + * be rare and it takes too much times here if not count + * the non-swapcache pages. + */ + if (unlikely(sc->swapcache_only && !is_file_lru(lru) && + !folio_test_swapcache(folio))) + goto move; + if (!folio_test_lru(folio)) goto move; if (!sc->may_unmap && folio_mapped(folio))