From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 03CE63E8678 for ; Thu, 23 Apr 2026 09:50:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776937801; cv=none; b=GMXeBJvenBIP01mFILpptlkoNtN7jwj9t+CfnpzztRfvEeohDwfhcQ+ZlCOzm/Visv6Z28gI3vMo/efjJqw2kyzfZhJam3p7o8anqgq7j+wW3vQ2hG89hNa1YY2nhNRF/GSb2q8OCUHDrmfvDnyXHeluflvqhlDPM7RCvFkb4WA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776937801; c=relaxed/simple; bh=0AvMl/HgDuU6+++EEE60wT7QZAwnlvC+1Uak1iqD4xc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Q2gKC6Z2c25n4gJu6dJbXqFWGGOIK3kYxYgTAcYRXzl2CnDAIBo6vZKC9fpHF8gYDY9Dmtpv24HpK9nwxzpRvBGbAP1KFUsZSiWVyW/i5dfVzPl8rEv+fgJe88WOgJWk4ERvDZ+MjEN8nKpmBQ8XmqvpZHHm6C42PWVS4xeUBAo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q7q2Q3nG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q7q2Q3nG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0E24DC2BCB7; Thu, 23 Apr 2026 09:49:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776937800; bh=0AvMl/HgDuU6+++EEE60wT7QZAwnlvC+1Uak1iqD4xc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Q7q2Q3nGsNvTyv8Vv/aO7WMV5WBRP9gzVxbwrZcs4ayzSXskMzNEZozwOzGNGAcLz gup7R4EMuWdNDDsYUoEaQDeuZu39P+WZvgLnmv6HQfzymHbaANub4skC6zHY+h6JUP EwgneY5LsCpv+u8w4+nonOVGY0wpg8f1BxIXUD0wu3jS5fGUuIRyddFKjTtox2we1H 2PM5zhfZPcAWbGB665+xe5hrX+x1IFMAEM5mZ4mK7ozYUp8foUbLZknMMwEjKOVdSi Bbw6oJzy0siRuFqHaI4ecvcx6En50gaBeb1QQ6swir2EWTD5bq8a5qXOdFQb4eWbBz AGiGv1wjg+9Yg== Message-ID: <28c3ae9f-c974-454c-b8ed-ba0ba0a5706d@kernel.org> Date: Thu, 23 Apr 2026 11:49:55 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/3] mm: process_mrelease: expedited reclaim and auto-kill support To: Michal Hocko , Minchan Kim Cc: akpm@linux-foundation.org, brauner@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, surenb@google.com, timmurray@google.com, Johannes Weiner References: <20260413223948.556351-1-minchan@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/23/26 09:50, Michal Hocko wrote: > On Mon 20-04-26 14:53:23, Minchan Kim wrote: >> On Fri, Apr 17, 2026 at 09:11:21AM +0200, Michal Hocko wrote: > [...] >>> Yes. All which make sense, really. I am still not convinced about the >>> clean page cache because that just seems like a hack to workaround wrong >>> userspace oom heuristics. >> >> I see it a bit differently. When paltform decides to kill a process >> to free up memory, they want that memory back right away. >> >> So it doesn't make much sense for the kernel to ignore that and leave the clean >> file pages to be picked up slowly by kswapd later. >> >> In some aspects, you can think of LMKD as a more specialized, userspace version >> of kswapd. It has high-level knowledge of process priorities and knows exactly >> which process is safe to kill to get memory instantly. The kernel's kswapd, >> however, operates globally without this specific process-level awareness, which >> makes it less suited for this kind of targeted reclamation. >> >> If we force LMKD to rely on the slower global kswapd to actually free the clean >> pages, it defeats the whole purpose of targeting a specific process. >> >> So letting process_mrelease speed this up isn't a hack at all. It's just helping >> the kernel do what the admin wanted in the first place: fast, targeted memory. > > This is a very creative/disruptive way to do a memory reclaim. From a > user POV I would much rather see clean page cache reclaimed before my > apps start to disappear. But this is obviously your call and your users > that will care. > > Anyway, I still maintain my position. I do not think it is a good > idea to drop clean page cache as you do not know whether there are other > users. IIRC, Johannes raised in the past the we cannot predict the future. For example, if an app gets OOM-killed, wouldn't we usually try restarting it, re-consuming the clean pagecache pages we would be evicting here? Just a thought. -- Cheers, David