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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1756140664; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rqpQFZwVyd9daGv2BdVpF249HwPEKam6Daue11hrMLM=; b=p1aRF4yqOC/7j0VRFHM24pw3foU2tCnV9UQ7nVEdYrizM09lraTGVSjjxLlIc+plnHQ/RY Yx06LjtEI/KECO6X2vcoPrNsi4VyVrLjDYSnAoPaQcX2VLxsfV286mDR0o2tLpAO2KkRN0 Mvr6xXXvwbUwBR22CFrD63CvEU4wtZ4= From: Roman Gushchin To: Jan Kara Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Matthew Wilcox (Oracle)" Subject: Re: [PATCH] mm: readahead: improve mmap_miss heuristic for concurrent faults In-Reply-To: (Jan Kara's message of "Mon, 25 Aug 2025 10:16:40 +0200") References: <20250815183224.62007-1-roman.gushchin@linux.dev> Date: Mon, 25 Aug 2025 09:50:58 -0700 Message-ID: <87cy8jz6od.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 963A4120011 X-Stat-Signature: fz6y3f1pnczabs4166hpqy4i4ba3qzce X-Rspam-User: X-HE-Tag: 1756140666-214738 X-HE-Meta: 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 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: Jan Kara writes: > On Fri 15-08-25 11:32:24, Roman Gushchin wrote: >> If two or more threads of an application faulting on the same folio, >> the mmap_miss counter can be decreased multiple times. It breaks the >> mmap_miss heuristic and keeps the readahead enabled even under extreme >> levels of memory pressure. >> >> It happens often if file folios backing a multi-threaded application >> are getting evicted and re-faulted. >> >> Fix it by skipping decreasing mmap_miss if the folio is locked. >> >> This change was evaluated on several hundred thousands hosts in Google's >> production over a couple of weeks. The number of containers being >> stuck in a vicious reclaim cycle for a long time was reduced several >> fold (~10-20x), as well as the overall fleet-wide cpu time spent in >> direct memory reclaim was meaningfully reduced. No regressions were >> observed. >> >> Signed-off-by: Roman Gushchin >> Cc: Matthew Wilcox (Oracle) >> Cc: Jan Kara >> Cc: linux-mm@kvack.org > > Looks good! Feel free to add: > > Reviewed-by: Jan Kara Thank you!