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Mon, 20 Apr 2020 15:19:41 +0900 (KST) Received: from [10.253.104.82] (unknown [10.253.104.82]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20200420061941epsmtip1a2c8e6a26c2181ac23609faa9af18fa0~HcsRhebsR1545015450epsmtip1s; Mon, 20 Apr 2020 06:19:41 +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: <5E9D3EFD.8030008@samsung.com> Date: Mon, 20 Apr 2020 15:19:41 +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: <5E9A3FB7.1040803@samsung.com> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrEJsWRmVeSWpSXmKPExsWy7bCmnu4/u7lxBrfvclnMWb+GzWL1Jl+L 7s0zGS0u75rDZnFvzX9Wi7VH7rJbTH73jNFiwfEWVotlX9+zW/y9sp7FYtnOfhaLx+u5HXg8 Dr95z+wxsfkdu8fOWXfZPTat6mTz2PRpErvHiRm/WTzW/XnF5PF+31U2j74tqxg9Np+u9vi8 SS6AOyrHJiM1MSW1SCE1Lzk/JTMv3VbJOzjeOd7UzMBQ19DSwlxJIS8xN9VWycUnQNctMwfo dCWFssScUqBQQGJxsZK+nU1RfmlJqkJGfnGJrVJqQUpOgaFBgV5xYm5xaV66XnJ+rpWhgYGR KVBlQk5G/6l/LAVrrSsWfHrO3MB4yqCLkZNDQsBEouPpOtYuRi4OIYEdjBKNz/azQTifGCXu NzxmgnC+MUp83r2QDaZl4+kFUC17GSUWrP4G5bxllFj1oIkZpEpYIFRiw/Ll7CC2iICXxOcV K8GKmAXuMUrM6OkHG8UmoC3xfsEkVhCbV0BL4uP5LWDNLAKqEm0bNoDViApESOyY+5ERokZQ 4uTMJywgNidQ79onB8BsZgF5ieats5lBFkgILGKX2PVjOyPErS4S87e+YYGwhSVeHd/CDmFL Sbzsb2OHaGhmlHg7czMjhNPCKHF3Uy9Ut7FEb88FoLEcQCs0Jdbv0ocIK0rs/D2XEWIzn8S7 rz2sICUSArwSHW1CECVqEi3PvrJC2DISf/89g7I9JBpPXWKHBNcfRolNm0+xT2BUmIXkuVlI HpqFsHkBI/MqRrHUguLc9NRiwwIT5FjexAhOz1oWOxj3nPM5xCjAwajEw8swe06cEGtiWXFl 7iFGCQ5mJRHeFJu5cUK8KYmVValF+fFFpTmpxYcYTYHhPZFZSjQ5H5g78kriDU2NjI2NLUzM zM1MjZXEeadez4kTEkhPLEnNTk0tSC2C6WPi4JRqYJxXfjfyz+nKHdxL+r59ynzzPWhzrKe7 5fLPhe9SnxuKrWEyr9ts/jd/VbPkudn5yeeehh3nnz3V+fT735XGbmtfder8+6bX9uGoU8Oh 7RNYs2Y3/VLYyC+pWxXPzO0fGXxg8QeXV42ld9i+3ez5e4qVKy9N4uwTAQ6pnCK/Pyr7r2s/ 676797wSS3FGoqEWc1FxIgDmxI8A5QMAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrIIsWRmVeSWpSXmKPExsWy7bCSnO5fu7lxBlt2alrMWb+GzWL1Jl+L 7s0zGS0u75rDZnFvzX9Wi7VH7rJbTH73jNFiwfEWVotlX9+zW/y9sp7FYtnOfhaLx+u5HXg8 Dr95z+wxsfkdu8fOWXfZPTat6mTz2PRpErvHiRm/WTzW/XnF5PF+31U2j74tqxg9Np+u9vi8 SS6AO4rLJiU1J7MstUjfLoEro//UP5aCtdYVCz49Z25gPGXQxcjJISFgIrHx9ALWLkYuDiGB 3YwS03dMYYRIyEi8Of+UpYuRA8gWljh8uBii5jWjRMu+lWA1wgKhEhuWL2cHsUUEvCQ+r1gJ NegPo8Shv6fAHGaBe4wS6/+/ZgOpYhPQlni/YBIriM0roCXx8fwWZhCbRUBVom3DBrAaUYEI idXrrjFD1AhKnJz5hAXE5gTqXfvkAJjNLKAu8WfeJWYIW16ieets5gmMgrOQtMxCUjYLSdkC RuZVjJKpBcW56bnFhgVGeanlesWJucWleel6yfm5mxjBEaeltYPxxIn4Q4wCHIxKPLwRc+fE CbEmlhVX5h5ilOBgVhLhTbGZGyfEm5JYWZValB9fVJqTWnyIUZqDRUmcVz7/WKSQQHpiSWp2 ampBahFMlomDU6qB0XetGlPx6QXb8ll9dzBb2f+ZcSd0qcbnwMiIOU4Nhkn7Nb+IcDx8dKCr nfWogY/aY+kXB2sWN4tyeEjypkiZFP7g51E6wJO8o3HbE9OPAX8+xBxZkHLwYF3a7yOFxU2N Fo3z3jULGW6YZsZjt2W11cxpGUIBzxT7tzKYFV9cPsH7oN1u3r49SizFGYmGWsxFxYkAB5OM orQCAAA= X-CMS-MailID: 20200420061941epcas1p2ee02814507dcdf504ffedc1090730d7f 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> 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 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 lazyf= ree >>>> page, then the lazyfree page is changed to a normal anon page having >>>> SwapBacked by commit 18863d3a3f59 ("mm: remove SWAP_DIRTY in ttu"). = Even >>>> with the change, reclaim context correctly counts isolated files bec= ause >>>> it uses is_file_lru to distinguish file. And the change to anon is n= ot >>>> happened if try_to_unmap_one is used for migration. So migration con= text >>>> 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 cleanu= p for >>>> MADV_FREE"). >>>> >>>> But the nr_isolate_* mismatch problem happens on cma alloc. There is >>>> reclaim_clean_pages_from_list which is being used only by cma. It wa= s >>>> introduced by commit 02c6de8d757c ("mm: cma: discard clean pages dur= ing >>>> contiguous allocation instead of migration") to reclaim clean file p= ages >>>> 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:1489= 2kB inactive_file:205636kB unevictable:10416kB isolated(anon):0kB isolate= d(file):37664kB mapped:630216kB dirty:384kB writeback:0kB shmem:42576kB w= riteback_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 file= in >>>> system wide. It could be reproducible by running two programs, doing >>>> MADV_FREE, writing and doing cma alloc, respectively. Although isola= ted >>>> 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. Th= e >>>> 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(st= ruct 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 othe= r > 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 l= ist_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(stru= ct 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(st= ruct 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 beginnin= g, >> + * they will rotate back to anonymous LRU in the end if it failed to >> + * 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_FREE= pages") , because I missed him/her on other mail thread=20 : Sorry, I think I pointed a wrong commit, the SwapBacked was recovered : 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_li= st()" for struct reclaim_stat. I considered other dependent changes below to follow code changes, not re= ally needed for this issue though. v5.3 98879b3b9edc mm: vmscan: correct some vmscan counters for THP swapou= t v5.2 886cf1901db9 mm: move recent_rotated pages calculation to shrink_ina= ctive_list() Thank you Jaewon Kim