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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: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 38D40180002 X-Stat-Signature: k89j944bsouka3u1ciui1f1k1q4eye6g X-Rspamd-Server: rspam01 X-HE-Tag: 1789901367-500171 X-HE-Meta: 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 KzKAGwCg guv9D1+r3e0O67EZ7B0ZBFcRKRG9aRMihY4vYPqJypLOtWd9PxsD1J4O1cHPuSVVFGbn48oDN7HQZgGyRLpUuQJUJDxD+bFmMaDEgyakv8xS1NX3HhbzyiTu9iWaZBhEr5ko3aSgz/60rG8XCKYU4bDI1CSPVBsW6aoQfxSLx47WGUnmmev7VtsEcV+L4sQ8GOwhhvXwIijyXSYDk7M8mKV91nlrdCJcE6t9p0+EQBhud3M3pAieK5ASWSumxcCykjV1mXdURVv1iwkaMBHqLTgwz8o/RMN7aGUsb+oT05u+YtLjh8rtfNnfZ+gdMtcffqBxJYLwviConGbPEbTP08shynQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 [...]