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 C096038FA3; Fri, 12 Sep 2025 12:45:52 +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=1757681152; cv=none; b=lHJIa1zNpb2LjjEpGyCHaHr68cCFr9nFSmVw19Jl4jHeniuuohFy/0wWwroTDiGYFzvz6e/EhiQBMi/QtLmXXe3nzby/lL3nQD1k2sF4WXlcmB2qYJ06Ac9xvg+Gf5vraeNa1VxycOkYufCFSfzfcEydxtLRbNLkNyQ/SnO/4gs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757681152; c=relaxed/simple; bh=lD5ROtoWeAtmKAISXqDN/6McT33HUmW9pjihJpJCvFs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=WQwz6R3vrdin7nkHeYWwoSqL1M45EEl47ID5RjroJheyQ0byiCxxoJ9H99WzpQuvnsWiY7EF1rRCeqvco/CSMfB4SAHfiYXZtsUe3LMgD2AkL4pgCcKUsci1dNvTEcqMnEG13w0VJXENQUJlH8lPHjfrsImf/vjtJLI2BsDHdU0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pi6wWXWm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="pi6wWXWm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDBCAC4CEF1; Fri, 12 Sep 2025 12:45:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1757681152; bh=lD5ROtoWeAtmKAISXqDN/6McT33HUmW9pjihJpJCvFs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pi6wWXWmQDtPgt2V60hAsaqZj1tVBkAvmTLZ+o3qpgRgmD2p03mdvdELPH70exUwF WYpG8IWw43ziWv9WR/YMz+vytLSkBPhkovit7iN7uZ6iSxIKa/qfTGalJR2rxwyw7V egJY3LU0VybbRWgl6Dm0NyepInCpRe3AAtOyUh9w= Date: Fri, 12 Sep 2025 14:45:49 +0200 From: Greg KH To: Andrew Guerrero Cc: akpm@linux-foundation.org, cgroups@vger.kernel.org, gunnarku@amazon.com, guro@fb.com, hannes@cmpxchg.org, roman.gushchin@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, shakeel.butt@linux.dev, muchun.song@linux.dev, stable@vger.kernel.org, vdavydov.dev@gmail.com Subject: Re: [PATCH] mm: memcontrol: fix memcg accounting during cpu hotplug Message-ID: <2025091216-purveyor-prior-2a81@gregkh> References: <2025090735-glade-paralegal-cdd1@gregkh> <20250908210900.24088-1-ajgja@amazon.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250908210900.24088-1-ajgja@amazon.com> On Mon, Sep 08, 2025 at 09:09:00PM +0000, Andrew Guerrero wrote: > On 2025-09-07 13:10 UTC, Greg KH wrote: > > On Sat, Sep 06, 2025 at 03:21:08AM +0000, Andrew Guerrero wrote: > > > This patch is intended for the 5.10 longterm release branch. It will not apply > > > cleanly to mainline and is inadvertantly fixed by a larger series of changes in > > > later release branches: > > > a3d4c05a4474 ("mm: memcontrol: fix cpuhotplug statistics flushing"). > > > > Why can't we take those instead? > > > > > In 5.15, the counter flushing code is completely removed. This may be another > > > viable option here too, though it's a larger change. > > > > If it's not needed anymore, why not just remove it with the upstream > > commits as well? > > Yeah, my understanding is the typical flow is to pull commits from upstream into > stable branches. However, I'm not confident I know the the answer to "which > upstream commits?" To get started, > > `git log -L :memcg_hotplug_cpu_dead:mm/memcontrol.c linux-5.10.y..linux-5.15.y` > > tells me that the upstream changes to pull are: > > - https://lore.kernel.org/all/20210209163304.77088-1-hannes@cmpxchg.org/T/#u > - https://lore.kernel.org/all/20210716212137.1391164-1-shakeelb@google.com/T/#u > > However, these are substantial features that "fix" the issue indirectly by > transitioning the memcg accounting system over to rstats. I can pick these 10 > upstream commits, but I'm worried I may overlook some additional patches from > 5.15.y that need to go along with them. I may need some guidance if we go this > route. Testing is key :) > Another reasonable option is to take neither route. We can maintain this patch > internally and then drop it once we upgrade to a new kernel version. Perhaps just do that for now if you all are hitting this issue? It seems to be the only report I've seen so far. thanks, greg k-h