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imf17.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf17.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1708068287; a=rsa-sha256; cv=none; b=QWy0wXWWkY8cRg5VmYKTNoXX1UJGQ5U7NRqx6/yh87pZYQEJzA05a9Sqg61C15pJNWqWVH nfARHetH+wq30D/oj1DaycfVtoUqbzuTiyEZiGOjnhrLH/Du8wGZW/8H4qMd2UfDDlfFgI nsD93njrSX3KmKnRF91tqYguMLNV2eg= X-AuditID: a67dfc5b-d6dff70000001748-6b-65cf0db7c462 Date: Fri, 16 Feb 2024 16:24:34 +0900 From: Byungchul Park To: Yu Zhao Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com Subject: Re: [PATCH] mm, vmscan: Don't turn on cache_trim_mode at the highest scan priority Message-ID: <20240216072434.GC32626@system.software.com> References: <20240208061825.36640-1-byungchul@sk.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrOLMWRmVeSWpSXmKPExsXC9ZZnoe523vOpBg8XmFvMWb+GzeLyrjls FvfW/Ge1eDfhC6sDi8eCTaUemz5NYvc4MeM3i8fnTXIBLFFcNimpOZllqUX6dglcGUenPGMq OCJYsW3TDpYGxl28XYycHBICJhIbrq5mhLG3nb3GBGKzCKhKXH7ZwApiswmoS9y48ZMZxBYR kJeY8PIZexcjBwezQJbE9NYoEFNYIFZi6cdwkApeAQuJH/2HwCYKCdRILP50lQUiLihxcuYT MJsZaOKfeZeYIaZISyz/xwERlpdo3jobbBGnQKDEs/UbwcaICihLHNh2HOgwLqAj57BJ3P25 kBXiYkmJgytusExgFJyFZMUsJCtmIayYhWTFAkaWVYxCmXlluYmZOSZ6GZV5mRV6yfm5mxiB wb2s9k/0DsZPF4IPMQpwMCrx8B74czZViDWxrLgy9xCjBAezkgjvpN4zqUK8KYmVValF+fFF pTmpxYcYpTlYlMR5jb6VpwgJpCeWpGanphakFsFkmTg4pRoY+R+cDQ4S/fdTqmbVlJ9f9Hjn JvQy6F/8XtTwJ5qN8btTRPQniWthtoEvtn9RbVi3f83PxmoTId6qk8GaTspCC7zX+gQ3mU5W vPIspfP1y083uBN3Cc/oMuCXfbDPdM5imXPibDOLb75pWs69h3lt2GfXvoqaYqH2mPWOTy4+ 9DM7kcXBoLxeiaU4I9FQi7moOBEAHPkeHGoCAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrHLMWRmVeSWpSXmKPExsXC5WfdrLud93yqwYnDBhZz1q9hszg89ySr xeVdc9gs7q35z2rxbsIXVgdWjwWbSj02fZrE7nFixm8Wj8UvPjB5fN4kF8AaxWWTkpqTWZZa pG+XwJVxdMozpoIjghXbNu1gaWDcxdvFyMkhIWAise3sNSYQm0VAVeLyywZWEJtNQF3ixo2f zCC2iIC8xISXz9i7GDk4mAWyJKa3RoGYwgKxEks/hoNU8ApYSPzoP8QIYgsJ1Egs/nSVBSIu KHFy5hMwmxlo4p95l5ghpkhLLP/HARGWl2jeOhtsEadAoMSz9RvBxogKKEsc2HacaQIj3ywk k2YhmTQLYdIsJJMWMLKsYhTJzCvLTczMMdUrzs6ozMus0EvOz93ECAzVZbV/Ju5g/HLZ/RCj AAejEg/vgT9nU4VYE8uKK3MPMUpwMCuJ8E7qPZMqxJuSWFmVWpQfX1Sak1p8iFGag0VJnNcr PDVBSCA9sSQ1OzW1ILUIJsvEwSnVwMhTNlft8QvJOGldjykvwqq6Ig86e7LNyjm1c+4hgcP3 36+W052cspz1FV84h4gJU7fhOr+dn8vMEz4ftt194/Z9bR8L6fa0Lp5vE19FPJjMK1x4u3OZ nKX3U+OZ1SJHvRbY89Xf+umi/PPfB52jP89nnHglVnDfZeaU+XnTly+1szjJ82ljdbYSS3FG oqEWc1FxIgAhchrLUQIAAA== X-CFilter-Loop: Reflected X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: CA0A740011 X-Stat-Signature: 9zz918ymbsdjxeb8fejsonwtiawytb9s X-Rspam-User: X-HE-Tag: 1708068284-98984 X-HE-Meta: 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 dLR4SKFd 6g1rI9fEABAGmBCnDdIXZi+HA3ESWQetJ2BV9+b4/pMHY0zqDJDRGHU2Nih+dH4zcqdHN 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 Fri, Feb 16, 2024 at 12:55:17AM -0500, Yu Zhao wrote: > On Thu, Feb 8, 2024 at 1:18 AM Byungchul Park wrote: > > > > With cache_trim_mode on, reclaim logic doesn't bother reclaiming anon > > pages. However, it should be more careful to turn on the mode because > > it's going to prevent anon pages from reclaimed even if there are huge > > ammount of anon pages that are very cold so should be reclaimed. Even > > worse, that can lead kswapd_failures to be MAX_RECLAIM_RETRIES and stop > > until direct reclaim eventually works to resume kswapd. > > Is a theory or something observed in the real world? If it's the > former, would this change risk breaking existing use cases? It's the I faced the latter case. > latter, where are the performance numbers to show what it looks like > before and after this patch? Before: Whenever the system meets the condition to turn on cache_trim_mode but few cache pages to trim, kswapd fails without scanning anon pages that are plenty and cold for sure and it retries 8 times and looks *stopped for ever*. After: When the system meets the condition to turn on cache_trim_mode but few cache pages to trim, kswapd finally works at the highest scan priority. So kswap looks working well even in the same condition. > > Signed-off-by: Byungchul Park > > --- > > mm/vmscan.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index bba207f41b14..25b55fdc0d41 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -2268,7 +2268,8 @@ static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc) > > * anonymous pages. > > */ > > file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE); > > - if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE)) > > + if (sc->priority != 1 && file >> sc->priority & > > Why 1? It means the highest scan priority. The priority goes from DEF_PRIORITY to 1. Byungchul > > + !(sc->may_deactivate & DEACTIVATE_FILE)) > > sc->cache_trim_mode = 1; > > else > > sc->cache_trim_mode = 0;