From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 085D82FD69D; Sun, 20 Sep 2026 10:49:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789901368; cv=none; b=RFOphqW5MLPBBbGMQiaHPclwSvFXS+/tTOT6xRRbq6cw9VDn2yA3ycDLTqOsZOS5Da0XYsVs8HuEIgVpx9jam8X7G0yBazaGly9QNdnslBV4gODY+SavzPbhUmImB/FYFR/VECSzhGDF7/nJmUU+i/bJve6xThkK7cjQ9MF65i8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789901368; c=relaxed/simple; bh=UkzeUPJIusodyzmatggs0A8U37oz4ka5GzFpPrHMbr4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Lf3/jqloAHANTuCioudjccQbonUKVq/Sw3rnN21rhMSY1+CwBhP596g666ux+fZs+6X6PWFapOXSInAgXTkszNfr6GmscPoPmuHMTQ+cVkVgffsHHvp81X93lGN5J4sHTPxiKRcbBEGgPWl/zP2uObCT4AzmznVVZMcIOHjd3EE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ikcr+qnW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ikcr+qnW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5CF271F000FF; Sun, 20 Sep 2026 10:49:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789901366; bh=JicpyNhz6N3EZ+HXyuGJGE/XahAzl0DJVcQ8CuCuwiM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Ikcr+qnWJfVqd2AgCrOOBMxrPGowMeVA+uVwPoanYFzc0rIQriUS+gZpQ0B+5RyHY g6qhWeXZkgdllHuM6l1ytBBw/6iIuopCsJgKRfWDeFi4bDbWJQRlMOzfQCGt/Z9IER psptqDk2r8Ot96aMNzlP2+xVQ7LuSKkgkxCPZ98OpnLM7hUKMoV+zvkct16xXcdzjN tvB7ZE0zQ0hikbPrZqjnWzVXrqFtnv5zZROTr1kHkiMv5jJfQ7moCOagMO6xw+558l 4GBrOimDySU1V/bzeIEEx9E4NmGlmvCnv8hEiGj5fFDb/zslGvpEKwZRxDhysko1fP PfsLVlMVkSglA== From: SJ Park To: Donggeun Yoo Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Randy Dunlap , linux-doc@vger.kernel.org Subject: Re: [PATCH v2 3/3] Docs/admin-guide/mm/damon/usage: document the temporal tuner's quota limit Date: Sun, 20 Sep 2026 03:49:20 -0700 Message-ID: <20260920104921.48065-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260920023111.2466265-4-donggeunyoo.kernel@gmail.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sun, 20 Sep 2026 11:31:11 +0900 Donggeun Yoo wrote: > The temporal goal tuner converts the size quota into basis points in an > unsigned long, so a quotas/bytes above ULONG_MAX / 10000 does not fit, > and is handled as if no size quota were set. On 32-bit that is 429496 > bytes, well below the "echo $((1024*1024*1024)) > quotas/bytes" this > document instructs. addr_unit does not raise the limit, though a larger > unit does make it harder to reach. > > Note both in the goal_tuner description. > > Signed-off-by: Donggeun Yoo > --- > Documentation/admin-guide/mm/damon/usage.rst | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst > index ba47255448564..ea7443b307826 100644 > --- a/Documentation/admin-guide/mm/damon/usage.rst > +++ b/Documentation/admin-guide/mm/damon/usage.rst > @@ -455,6 +455,13 @@ the background design of the feature and the name of the selectable algorithms. > Refer to :ref:`goals directory ` for the goals > setup. > > +The ``temporal`` algorithm converts the size quota into basis points, so it > +cannot represent a ``bytes`` value larger than 429496 on 32-bit kernels, or > +1844674407370955 on 64-bit ones. This feels like too much implementation details. > Larger values are handled as if no size > +quota were set. I don't get what this means. > :ref:`addr_unit ` does not raise the > +limit, but it does make the limit harder to reach: with a larger unit, the > +same amount of memory is written to ``bytes`` as a smaller number. I suggested it might make sense to document this problem, but now I doubt if this is really helpful for users. Given the fact that the issue can happen on only untested setups, I now think this documentation change is better not to be made. Correct me if I'm wrong. If I'm not incorrect, could we drop this patch? Thanks, SJ [...]