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WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <87h6lzy68z.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.24] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemd200004.china.huawei.com (7.185.36.141) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0069C160016 X-Stat-Signature: 1topigwwq7rk5n9crbk31k9fx7suau8r X-HE-Tag: 1699253087-913274 X-HE-Meta: U2FsdGVkX19pNGDYnf/soNAcjYdEDTkZLTGNdqvyj0A118vyr7sj77l8641EYfh6ZYtqSJXVzG5oz6vl0XfrpgAOEv3e7c/LvzQhkXw5TY+JHPacEkNjzJO6mazwfTMwq9ZEGauKYOuLMUV7da7E9BaLGx3iQesLxoV+NEr/uzzOmrod+jerxJg6oaBEGzAxTnpBf3MXgm1o0Bs1PphvrZAonxA+l5eAriCbv7olzsSNmQR4qFT6QzYFFT8PDtf4zaAjq/88RCgPX/Hfo8Md51zwQjVSbN+Pbu7+NM5c1NJChGZiCZALdI180pB0D9gWwsfWSREsNTBZw5jRy6aF8a29FTnPzUg5JU+HJT4/FcKh6fh+1+c4c8epeesZ3SumC9LZkIMrfyF2A69x55w3K/vuxkPPZNRCV5PlrV2wcbnhpSKKke/VKmxCU9gxL+DdQE48z6wW1pj/pcuaeXz37AHHLVr8KwQWIp51dWxK55BNOucdQxO+q1k3q7bim2oLAjnGrDGRSrCB3dGHH/G5LI8xAMI5p7y6aN1KKutohYnMYQwMJ9x6u4HJMxFjA/dow7PD6oD08AGP2MLjRDxTSgh0RPqDVJMCKypBDmqCXDPTkoiTmwVocgzkKlGE5XWeaa9MP9KDodmSc5/q5H+VTWmLzDGSk4xz4twTJnfj8x8O8j/ZeQa4eD5yme1kh26oS/UWnjmaLuL1wAyH8xcnjrFzACplJ1KXmmf/3M6YoQ3YuVrcjJd7BAriJsbUd71lWwkRxzyMY6DmMiQiHNxG0PmRz4fYhS3qyfvgtm8ojWjLDO09WERRK210MOQpZFc5FIcRZUUsBzSdHrdvFsfesb0e9MXjHyGjZqP6LjeiJNkbrc0vuqV0ayQMx7TYJ3wqb2A/CL0VjO+t+paxjq3xRaZfkwfQdh5h2McoJyxi52yUVkH4AxdPPCRP5iIBJgSqHUzE34DexYczU4uw4gi lxl11jjA 7ItJ1Bl5u1l1Q0MsOHQC87KeY5hvzDAL/qTZ975WEgo7hn6Ql6rObPFcS/SqrNlYXP74kZdy3uV41mJ0Ep1nkVnOGTeC8CgvgK3r8fGworsHg7Jw+Au/yH0UjzqnMseRYL4xY0Q+n+k0FcxCyvXoZzWh+VrCBKXPwFXbIph5Au/xAp6be4VuZHPOOmkhIW68XDG4yHR4Fs39x8KDy//Lvr5q1hSe86vBgzTAFLBG2LSNZwtowb5TM9hJj6Dq9+TvEVRZBheBUXDm44tJn0Rk8i6B8RQ== 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: On 2023/11/6 10:18, Huang, Ying wrote: > Liu Shixin writes: > >> 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 >> --- >> 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 | 36 ++++++++++++++++++++++++++++++++++-- >> 3 files changed, 48 insertions(+), 2 deletions(-) >> >> 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..a5e04291662f 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; >> >> @@ -602,6 +605,12 @@ static bool can_demote(int nid, struct scan_control *sc) >> return true; >> } >> >> +static void set_swapcache_mode(struct scan_control *sc, bool swapcache_only) >> +{ >> + if (sc) >> + sc->swapcache_only = swapcache_only; >> +} >> + > I think that it's unnecessary to introduce a new function. I understand > that you want to reduce the code duplication. We can add > > sc->swapcache_only = false; > > at the beginning of can_reclaim_anon_pages() to reduce code duplication. > That can cover even more cases IIUC. OK, it‘s more appropriate, I will resend v8, thank you. >> static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, >> int nid, >> struct scan_control *sc) >> @@ -611,12 +620,26 @@ static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, >> * For non-memcg reclaim, is there >> * space in any swap device? >> */ >> - if (get_nr_swap_pages() > 0) >> + if (get_nr_swap_pages() > 0) { >> + set_swapcache_mode(sc, false); >> return true; >> + } >> + /* Is there any swapcache pages to reclaim? */ >> + if (total_swapcache_pages() > 0) { >> + set_swapcache_mode(sc, true); >> + return true; >> + } >> } else { >> /* Is the memcg below its swap limit? */ >> - if (mem_cgroup_get_nr_swap_pages(memcg) > 0) >> + if (mem_cgroup_get_nr_swap_pages(memcg) > 0) { >> + set_swapcache_mode(sc, false); >> return true; >> + } >> + /* Is there any swapcache pages in memcg to reclaim? */ >> + if (mem_cgroup_get_nr_swapcache_pages(memcg) > 0) { >> + set_swapcache_mode(sc, true); >> + return true; >> + } >> } > If can_demote() returns true, we shouldn't scan swapcache only. > > -- > Best Regards, > Huang, Ying > >> /* >> @@ -2342,6 +2365,15 @@ 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)) > . >