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b=YLKbqTlUiEIfPSLrLbDmry7Ju7Qr4sAg0DG1Tvb5SxxdYt9lh3pqVwUKCaWeGvWNq mS88ZoRJgGz1LICYjIJ1N2gpwU5syglw76yA+qErf8zngGv5NLKjCAxcBO3PdU0Xi1 l/cG+nADFoA9BNGm4ZXfSvaP8YdSAV9SIvSZ51/fJO7yyQq6ryAmqhgt6eWLrcqa2v vLvci7U50uALn1JP+JwYfzv1zOzFp0JRPxgUSXuyUszPgNFn8a17g4v5YlA+ujRP9g xglV3RkBI+ns5CixXMLbMbnBHm6Gn2fpi2OlSYI/+jDDtjD0E+7pRpe4nIp8lJsAtT WqGF/OKsucx6w== From: SeongJae Park To: SeongJae Park Cc: "# 5 . 16 . x" , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: (sashiko review) [RFC PATCH] mm/damon/core: use time_in_range() for damos quota window start Date: Sat, 28 Mar 2026 10:03:21 -0700 Message-ID: <20260328170321.48340-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260328170008.48144-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 148B540016 X-Stat-Signature: b4q5173ct78imy4zy75dn6yc79t8gj99 X-Rspam-User: X-HE-Tag: 1774717403-961389 X-HE-Meta: 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 k/0QzSfm d7oB5qWy548eU75gvEBhPqBVik1ABEfT4HLq9HXAOdhtBUnPKgHXX58lSaHFU8Niczzk5XVmxYwTt6CL9AIWzEN+aR/g4dGEVrvwyG4K6Ho6xCeO+XK6zrLRW5kiKjJFGpPGylrJYpetauBEoo64RpWVyBFbxixP4KmcaiQfFzGx2zivKd4TKDdrcJhUZvEd8yfIvGEb/OLNROR3lDlFGZ2wVk+nmvhEPH6WXDFX4OfjZ+v6Hhqp9DjpeLbRcGQxqLDR4RH4Cb+kf9cuRq5Mgno30cTJDNdKFVkrVPa2I8UUkA0Y= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 28 Mar 2026 10:00:08 -0700 SeongJae Park wrote: > Forwarding Sashiko review for doing discussions via mails. > > # review url: https://sashiko.dev/#/patchset/20260328163930.47096-1-sj@kernel.org > # start of sashiko.dev inline review > commit 2ee07f5a4fcf25b39aeac61c6b88fe3fdfd0c9b6 > Author: SeongJae Park > > mm/damon/core: use time_in_range() for damos quota window start > > This commit attempts to fix a stall in DAMOS quota charge windows when > a scheme is deactivated for more than LONG_MAX jiffies. It replaces > time_after_eq() with !time_in_range() to properly handle the extended > time wrap-around. > > Link: https://lore.kernel.org/20260324040722.57944-1-sj@kernel.org > > > diff --git a/mm/damon/core.c b/mm/damon/core.c > > index db6c67e52d2b..8e47183473d3 100644 > > --- a/mm/damon/core.c > > +++ b/mm/damon/core.c > > @@ -2452,7 +2452,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) > > } > > > > /* New charge window starts */ > > - if (time_after_eq(jiffies, quota->charged_from + > > + if (!time_in_range(jiffies, quota->charged_from, quota->charged_from + > > msecs_to_jiffies(quota->reset_interval))) { > > Does this introduce an off-by-one regression that extends every quota charge > window by 1 jiffy? > > time_in_range(a, b, c) evaluates the inclusive interval [b, c], which means > it returns true when jiffies exactly equals the end of the interval. The > original code used time_after_eq(), which correctly triggered the new > charge window exactly on that jiffy. > > By replacing it with !time_in_range(), the reset evaluates to false on that > exact jiffy and is delayed until the next jiffy. For small reset_interval > configurations or low CONFIG_HZ values, this 1-jiffy delay might alter the > effective quota replenishment rate. The effect should be negligible, but good finding. > > Would using !time_in_range_open() preserve the exact original timing > semantics while still fixing the wrap-around stall issue? Good suggestion, I will do so in the next revision. Thanks, SJ [...]