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Wed, 19 Aug 2026 03:16:00 +0000 X-Migadu-Flow: FLOW_OUT Message-ID: <9a92b4c9-ad33-492a-b206-2b0862585c64@linux.dev> Date: Wed, 19 Aug 2026 11:15:52 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/oom_kill, proc: replace magic number 1000 with OOM_SCORE_ADJ_MAX To: Song Hu Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liuye@kylinos.cn, mhocko@suse.com, rientjes@google.com, shakeel.butt@linux.dev References: <20260811033609.3992348-1-ye.liu@linux.dev> <20260818010433.65169-1-husong@kylinos.cn> Content-Language: en-US From: Ye Liu In-Reply-To: <20260818010433.65169-1-husong@kylinos.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: w3yn9uui7677dne3emgxbtppg3pg1d97 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E06451C0007 X-HE-Tag: 1787109361-409996 X-HE-Meta: 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 my5bWiQH BqVmJG/shgY3lcRNOHtuevZWIhFmA9nFLOqFyt53+TGGltvyGPCE/Q1bQXEitJLnLiFKvg98Rdi3XLXLIGhHPyVI53BR/oN1hsrK66UPCMDC/pVgt6QME1U8AyPZuHGOpHDMPh4yvg3NfvAYSkkLZ7Jn/5Wn/g8ZEUN2xDxTk3x6xsGQutDY9DSOCpNODoDh6iUpbfBNRDOw9p8QQgBBSY/okiQiOOBsT3ETvnI0XkI7wN2a+GK0ER2UGv7j+muk/+ylpzZTgE9LPu7u/I9AbssiCisPM1snTfEWUZ9DSjCyuLUUXKuTiwVe2MHnHKI4GyRNCvWf+8l47dkC4zliF8ylAS1uk/sAMp96m Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/8/18 09:04, Song Hu 写道: > On 2026/8/11 11:36, Ye Liu wrote: >> --- a/mm/oom_kill.c >> +++ b/mm/oom_kill.c >> @@ -230,7 +230,7 @@ long oom_badness(struct task_struct *p, unsigned long totalpages) >> task_unlock(p); >> >> /* Normalize to oom_score_adj units */ >> - adj *= totalpages / 1000; >> + adj *= totalpages / OOM_SCORE_ADJ_MAX; > > One thing this line hides: for a memcg OOM, totalpages is > mem_cgroup_get_max(), which can be below 1000 pages when the > container limit is under 4M. The division then yields 0, the whole > oom_score_adj contribution goes away, and a task protected with > -997 scores the same as a best-effort task with 1000. The -1000 > exemption is checked separately above and still works. > > DIV_ROUND_UP(totalpages, OOM_SCORE_ADJ_MAX) would preserve the adj > weighting for small limits and change nothing meaningful for large > ones. This is an edge case, so probably fine to leave as is - > noting it here since the line is being touched anyway. Good catch. Yes, the truncation for totalpages < 1000 is real, but as you noted, it's an existing edge case. I'll keep this patch as a mechanical replacement and won't address it here. Out of curiosity, are sub-4MB memcg limits actually used in practice? -- Thanks, Ye Liu