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b=MiP7VDcRQNxMZAViYh9ABN4d1iXEi+V+WYJvnsLJAWfhT+7QAEotrRl6/3uITknyl 6ttkv7XDTs0ivbLlBK3OAqzmDL9aj7TLgOpOkmxJYOqmcfG6CiWZX0VRwITgxVfG9O Ai0TSUZsRilaiaPW83IHQgYwu6lIZpA/s5BpV38Q8m2y40zOoOBC0Qu9oVv4AN72TB S46vabyDMQ5O725glZrJD9WbtjIOYpUauf3tuqnzBHLQN4aGPyd5VYRN1+7p4+kE4p uW4LOKg+ciwSt4XlhEXu+ClA50kwYL0IpZxAPoQnsuUsDECimD0zW5p1MueQwKA+HO qD+IjFaOgQtqw== From: SeongJae Park To: Karthikeyan KS Cc: SeongJae Park , Sang-Heon Jeon , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/damon: reject zero sampling interval Date: Thu, 17 Sep 2026 19:38:58 -0700 Message-ID: <20260918023859.13556-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260917180013.1279018-1-karthiproffesional@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 63F43140002 X-Stat-Signature: tj5cjuyk3ejhgrrqnkmm16gr8xczgyw8 X-Rspam-User: X-HE-Tag: 1789699142-245096 X-HE-Meta: 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 D6pwqBEz dUvdUhYPiiT+JpFz3u0qpBPU/tX8SnZ+bgotSFsURr1H8ZjNSF8hlGKipTaYyxMcEJ3MY2BBGU1yDsL+UUfWkWucF+HRA9yOuvHoPpK1ntyd2g7qGSmJ96/I/vNPSYkh2Ujsnijby+VTkQvyBT+tBE4qFUL274a48vv3Q7TpNgvA8pjPyAg2GpWd+NV+UiOG/m4QwHTNXQjr++bMz2F00Wfzxs4Mxc7ybB2TYtH0l+Iim7A2k7izMRkW6JxSonj7lkvdiD8mm6WzpR184OGOq7RG/sw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Karthikeyan and Sang-Heon, On Thu, 17 Sep 2026 18:00:13 +0000 Karthikeyan KS wrote: > Hi Sang-Heon, Hi SJ, > > > I think SJ already commented on a similar patch. please refer to [1] > > > > [1] https://lore.kernel.org/all/20260722094304.3132750-1-dayou5941@163.com/ Thank you for pointing this out, Sang-Heon! > > Thanks, missed that thread. Same objection applies to mine. > > > Can't we keep supporting zero sample interval and fix the warning > > or the real bug instead? > > I measured a few floors for kdamond_usleep(): > > floor kdamond CPU (3s) vs sample_us=5000 > 1us 84% 28x > 100us 42% 14x > 1000us 12% ~3x > 5000us ~2% 1x (matches control) > > 5000us is damon_new_ctx()'s own default, and at that floor the spin > is just gone. > > Would you rather we just document sample_us=0 as accepted/expected > behavior, or clamp it to that default inside damon_set_attrs()? I'd prefer adding a comment saying zero sampling interval is accepted. I think damon_attr kernel-doc comment is a good place for adding that. Thanks, SJ [...]