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Tue, 21 Apr 2020 21:06:37 +0900 (KST) Received: from [10.253.104.82] (unknown [10.253.104.82]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20200421120637epsmtip17d2563f3506bdff32122706868136c0c~H1EeBhM0C1437214372epsmtip1S; Tue, 21 Apr 2020 12:06:37 +0000 (GMT) Subject: Re: [PATCH] mm/vmscan: skip layzfree page on reclaim_clean_pages_from_list To: Minchan Kim , Johannes Weiner Cc: mgorman@suse.de, m.szyprowski@samsung.com, mina86@mina86.com, riel@redhat.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com, ytk.lee@samsung.com, shli@fb.com From: Jaewon Kim Message-ID: <5E9EE1CD.1030809@samsung.com> Date: Tue, 21 Apr 2020 21:06:37 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <5E9D3EFD.8030008@samsung.com> X-Brightmail-Tracker: H4sIAAAAAAAAA01Ta0zTUBTmrl1bYDN1iN4QlVnURAy6MofVCDHxkUYxkhgT4mNYoAK6dXMd RjQkEhaCE5koGhmCaCLofAwHGjDxEXzgez4jPmYkKlFEiBCM+EDXFSP/vnPu953znXPvJRDN fSyGyBPsvE3gTBQWgV64NkOX8KCz1qh7VE4yh72nMeaUbwWzu6kKME8uHsaYN6f/KJkz1wM4 s7+3CzB17Q4lUz/YhzO/n3pRpr7VhTLvvJELVey1nj6ErSjuxdlWdwBnfZ5dGOvr34eztw79 RNmzv7oVbN/lZxhb3uwBbNPdHeyAb3Ja5BrTglyey+ZtWl7IsmTnCTnJ1PJVGYsyDEk6OoGe x8yltAJn5pOpxalpCUvzTEHrlHYrZ8oPptI4UaRmpyywWfLtvDbXItqTKd6abbLSOusskTOL +ULOrCyLeT6t0yUagswNptxddwqtxSnbPGfUO0F/ohMQBCTnwNJSrRNEEBqyBcAnzeW4HPQD eLnHNRJ8A7D9403ECcJDiqHOBqWENeQlAD/3CzLpC4CB4UZMOogiV8PGhgZcwuPIZXDgxEml RELINwAeKnOFSBg5E/bV7QtVUpPxsN7/EpU8oeQ06PTlSeloMh221HwFMmUsvF31HpVweFDq ft8RkiJkLCw+X41I9SF5DIcvHGcVstPF0O8vwWQcBbvbm3EZx8BPrhJcFhQD+KWqCciBIziC bw+QWXq4p+whIjlCyBnQe3G2nJ4CW3/WALnzGNg7WKaUF6mGpSUamTIdOroGlTKeCH8Pd41g FhbdeTyy0moFLG30KvYCrXvUcO5RA7n/d64DiAeM562iOYcXaSs9+oJ9IPSU4w0toPJBahsg CUCp1B3+WqNGyW0VC8xtABIINU6d3hFMqbO5gu28zZJhyzfxYhswBNddgcREZ1mCH0OwZ9CG RL1ez8xJmptk0FMT1Aeem4waMoez85t53srb/ukURHjMTrAazxRi/TfAklcqoiAu8+C5wNpo YyX6+FWEvejHpW03mj5FpA4kbR+zu/CK/3jK+ueZ9Z2VYY4tLUNHV354uiH97b2hRmN39e2J Ro/qalWP6zUdtnlTuG35pBoVduvzQaErzrduXq2xMDA5TnElPWqqYv+6jZFHvjNtPwaWOsOO n1pGoWIuR8cjNpH7C5AhqWPgAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprLIsWRmVeSWpSXmKPExsWy7bCSnO7Zh/PiDKZe1bCYs34Nm8XqTb4W 3ZtnMlpc3jWHzeLemv+sFmuP3GW3mPzuGaPFguMtrBbLvr5nt/h7ZT2LxbKd/SwWj9dzO/B4 HH7zntljYvM7do+ds+6ye2xa1cnmsenTJHaPEzN+s3is+/OKyeP9vqtsHn1bVjF6bD5d7fF5 k1wAdxSXTUpqTmZZapG+XQJXRuep2oJmu4pVa3kbGD8ZdTFyckgImEj8fLictYuRi0NIYDej xLfeHYwQCRmJN+efsnQxcgDZwhKHDxdD1LxmlLj16iYbSI2wQKjEhuXL2UFsEQEvic8rVrKC 2EICs5kkDt7XB2lgFrjHKLH+/2uwBjYBbYn3CyaBFfEKaEksO38LbAGLgKpE16ZMkLCoQITE 6nXXmCFKBCVOznzCAmJzArXOenIDrJVZQF3iz7xLzBC2vETz1tnMExgFZyFpmYWkbBaSsgWM zKsYJVMLinPTc4sNCwzzUsv1ihNzi0vz0vWS83M3MYIjTUtzB+PlJfGHGAU4GJV4eG+cnxcn xJpYVlyZe4hRgoNZSYQ34gZQiDclsbIqtSg/vqg0J7X4EKM0B4uSOO/TvGORQgLpiSWp2amp BalFMFkmDk6pBsbCOHbXxPDGPo3bTFdYX397JfNRhbF80d6rF/S3fBFxlHy1Yu6xe2s5mBTN Th7fE+UpX1G/v09nR/i/pohjT7cWfQvbfq952hruzVsfRd5vW2i4WeL+xL7mP752pl+3RPLI 8tSUn/Kdero8tcTMbVqykuHxgFcP9lS97TT4eq3U+njHu8krAr4psRRnJBpqMRcVJwIAkLG4 B7ACAAA= X-CMS-MailID: 20200421120637epcas1p4cf390cc70a1a0b7eb38bfa2050e4b705 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200416033543epcas1p2b256bef770bb1310a9bf62bda80a976a References: <20200416033514.6366-1-jaewon31.kim@samsung.com> <20200417003837.GA90471@google.com> <20200417151358.GA178621@google.com> <5E9A3FB7.1040803@samsung.com> <5E9D3EFD.8030008@samsung.com> Content-Transfer-Encoding: quoted-printable 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: On 2020=EB=85=84 04=EC=9B=94 20=EC=9D=BC 15:19, Jaewon Kim wrote: > > On 2020=EB=85=84 04=EC=9B=94 18=EC=9D=BC 08:45, Jaewon Kim wrote: >> On 2020=EB=85=84 04=EC=9B=94 18=EC=9D=BC 00:13, Minchan Kim wrote: >>> On Thu, Apr 16, 2020 at 05:38:37PM -0700, Minchan Kim wrote: >>>> Hi Jaewon, >>>> >>>> On Thu, Apr 16, 2020 at 12:35:14PM +0900, Jaewon Kim wrote: >>>>> This patch fix nr_isolate_* mismatch problem between cma and dirty >>>>> lazyfree page. >>>>> >>>>> If try_to_unmap_one is used for reclaim and it detects a dirty lazy= free >>>>> page, then the lazyfree page is changed to a normal anon page havin= g >>>>> SwapBacked by commit 18863d3a3f59 ("mm: remove SWAP_DIRTY in ttu").= Even >>>>> with the change, reclaim context correctly counts isolated files be= cause >>>>> it uses is_file_lru to distinguish file. And the change to anon is = not >>>>> happened if try_to_unmap_one is used for migration. So migration co= ntext >>>>> like compaction also correctly counts isolated files even though it= uses >>>>> page_is_file_lru insted of is_file_lru. Recently page_is_file_cache= was >>>>> renamed to page_is_file_lru by commit 9de4f22a60f7 ("mm: code clean= up for >>>>> MADV_FREE"). >>>>> >>>>> But the nr_isolate_* mismatch problem happens on cma alloc. There i= s >>>>> reclaim_clean_pages_from_list which is being used only by cma. It w= as >>>>> introduced by commit 02c6de8d757c ("mm: cma: discard clean pages du= ring >>>>> contiguous allocation instead of migration") to reclaim clean file = pages >>>>> without migration. The cma alloc uses both reclaim_clean_pages_from= _list >>>>> and migrate_pages, and it uses page_is_file_lru to count isolated >>>>> files. If there are dirty lazyfree pages allocated from cma memory >>>>> region, the pages are counted as isolated file at the beginging but= are >>>>> counted as isolated anon after finished. >>>>> >>>>> Mem-Info: >>>>> Node 0 active_anon:3045904kB inactive_anon:611448kB active_file:148= 92kB inactive_file:205636kB unevictable:10416kB isolated(anon):0kB isolat= ed(file):37664kB mapped:630216kB dirty:384kB writeback:0kB shmem:42576kB = writeback_tmp:0kB unstable:0kB all_unreclaimable? no >>>>> >>>>> Like log above, there was too much isolated file, 37664kB, which >>>>> triggers too_many_isolated in reclaim when there is no isolated fil= e in >>>>> system wide. It could be reproducible by running two programs, doin= g >>>>> MADV_FREE, writing and doing cma alloc, respectively. Although isol= ated >>>>> anon is 0, I found that the internal value of isolated anon was the >>>>> negative value of isolated file. >>>>> >>>>> Fix this by skipping anon pages on reclaim_clean_pages_from_list. T= he >>>>> lazyfree page can be checked by both PageAnon(page) and >>>>> page_is_file_lru. But in this case, PageAnon is enough to skip all >>>>> anon pages. >>>>> >>>>> Reported-by: Yong-Taek Lee >>>>> Signed-off-by: Jaewon Kim >>>> Thanks for the investigation! >>>> The thing is MADV_FREEed page since supporting swapless could change >>>> his LRU status between reclaim. >>>> >>>> I am worry about voiding the optimization we have kept in CMA but >>>> also don't have good idea, either so I tend to agree with this. >>>> >>>> Let me Cc Johannes who might have better idea. >>>> >>>>> --- >>>>> mm/vmscan.c | 3 +++ >>>>> 1 file changed, 3 insertions(+) >>>>> >>>>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>>>> index b06868fc4926..9380a18eef5e 100644 >>>>> --- a/mm/vmscan.c >>>>> +++ b/mm/vmscan.c >>>>> @@ -1497,6 +1497,9 @@ unsigned long reclaim_clean_pages_from_list(s= truct zone *zone, >>>>> LIST_HEAD(clean_pages); >>>>> =20 >>>>> list_for_each_entry_safe(page, next, page_list, lru) { >>>>> + /* to avoid race with MADV_FREE anon page */ >>>>> + if (PageAnon(page)) >>>>> + continue; >>>>> if (page_is_file_lru(page) && !PageDirty(page) && >>>>> !__PageMovable(page) && !PageUnevictable(page)) { >>>>> ClearPageActive(page); >>>>> --=20 >>>>> 2.13.7 >>>>> >>> Hi Jaewon, >>> >>> How about this idea? I think it could solve the issue with keeping >>> CMA alloc latency optimization. >> Hello Minchan >> >> It looks good to me except compilation error. >> >> And to apply this patch on other stable branches, we may need some oth= er >> dependent patches though. >> >> Thank you >>> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h >>> index 292485f3d24d..10cc932e209a 100644 >>> --- a/include/linux/vmstat.h >>> +++ b/include/linux/vmstat.h >>> @@ -29,6 +29,7 @@ struct reclaim_stat { >>> unsigned nr_activate[2]; >>> unsigned nr_ref_keep; >>> unsigned nr_unmap_fail; >>> + unsigned nr_lazyfree_fail; >>> }; >>> =20 >>> enum writeback_stat_item { >>> diff --git a/mm/vmscan.c b/mm/vmscan.c >>> index 4c8a1cdccbba..b390f6094f2f 100644 >>> --- a/mm/vmscan.c >>> +++ b/mm/vmscan.c >>> @@ -1296,11 +1296,15 @@ static unsigned long shrink_page_list(struct = list_head *page_list, >>> */ >>> if (page_mapped(page)) { >>> enum ttu_flags flags =3D ttu_flags | TTU_BATCH_FLUSH; >>> + bool lazyfree =3D PageAnon(page) && !PageSwapBacked(page); >>> =20 >>> if (unlikely(PageTransHuge(page))) >>> flags |=3D TTU_SPLIT_HUGE_PMD; >>> + >>> if (!try_to_unmap(page, flags)) { >>> stat->nr_unmap_fail +=3D nr_pages; >>> + if (lazyfree && PageSwapBacked(page)) >>> + stat->nr_lazyfree_fail +=3D nr_pages; >>> goto activate_locked; >>> } >>> } >>> @@ -1492,8 +1496,8 @@ unsigned long reclaim_clean_pages_from_list(str= uct zone *zone, >>> .priority =3D DEF_PRIORITY, >>> .may_unmap =3D 1, >>> }; >>> - struct reclaim_stat dummy_stat; >>> - unsigned long ret; >>> + struct reclaim_stat stat; >>> + unsigned long reclaimed; >>> struct page *page, *next; >>> LIST_HEAD(clean_pages); >>> =20 >>> @@ -1505,11 +1509,21 @@ unsigned long reclaim_clean_pages_from_list(s= truct zone *zone, >>> } >>> } >>> =20 >>> - ret =3D shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, >>> - TTU_IGNORE_ACCESS, &dummy_stat, true); >>> + reclaimed =3D shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, >>> + TTU_IGNORE_ACCESS, &stat, true); >>> list_splice(&clean_pages, page_list); >>> - mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret); >>> - return ret; >>> + mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -reclaimed)= ; >>> + /* >>> + * Since lazyfree pages are isolated from file LRU from the beginni= ng, >>> + * they will rotate back to anonymous LRU in the end if it failed t= o >>> + * discard so isolated count will be mismatched. >>> + * Compensate the isolated count for both LRU lists. >>> + */ >>> + mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON, >>> + stat->nr_lazyfree_fail); >>> + mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, >>> + -stat->nr_lazyfree_fail); >> should be stat.nr_lazyfree_fail and -stat.nr_lazyfree_fail instead of = -> >>> + return reclaimed; >>> } >>> =20 >>> /* > Let me just CC Shaohua Li for commit 802a3a92ad7a ("mm: reclaim MADV_FR= EE pages") > , because I missed him/her on other mail thread=20 > : Sorry, I think I pointed a wrong commit, the SwapBacked was recovere= d > : by commit 802a3a92ad7a ("mm: reclaim MADV_FREE pages"). > > > Hello Minchan > > I tested on my v4.19 based source tree and it seems to work. > > Prior to your patch I applied commit 060f005f0747 ( > "mm/vmscan.c: do not allocate duplicate stack variables in shrink_page_= list()" > for struct reclaim_stat. > > I considered other dependent changes below to follow code changes, not = really needed for this issue though. > v5.3 98879b3b9edc mm: vmscan: correct some vmscan counters for THP swap= out > v5.2 886cf1901db9 mm: move recent_rotated pages calculation to shrink_i= nactive_list() Hello Minchan Are you preparing a complete patch for this issue? Sorry if I am bugging you. > > Thank you > Jaewon Kim > >