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b=SN3KVN+OmG+YdSHj8RmFq7bQsp31iwYIqyzerCEi4S9YLr2aGW6GrarlYu8N5KfpI PRLxMH7RFr4ZHzgAh6nlDxuKg1wsVfg+7+ir2lAuUz+paDQgrva9SUc7VK3PMybwC6 LZm5O3+qfN79znFh/walN/wYHuKcZIPu4XL+hu8KbvZhOOdLgUM9xblR5u8EShTrGl OhjnVG9KbVI/iG9yDYAJGrE0ZtonMUd3CcYMOz25f601ogVQi0zfDerCkOpdJLsnsG WgJLI7g2BS+Wio+EhVuUJzaY4hhSjo1HaCFGPEB5u9XJzHWkPlXPQkScIN0lVViTc3 FM6Z/DJz5l/yA== From: SeongJae Park To: Ravi Jonnalagadda Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, bijan311@gmail.com, ajayjoshi@micron.com, honggyu.kim@sk.com, yunjeong.mun@sk.com Subject: Re: [RFC PATCH 3/5] mm/damon/core: floor effective quota size at minimum region size Date: Sun, 17 May 2026 11:47:04 -0700 Message-ID: <20260517184705.4652-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260516210357.2247-4-ravis.opensrc@gmail.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 48F0120005 X-Stat-Signature: sgdw9mwtwcuwq73bygeemupt3158trca X-Rspam-User: X-HE-Tag: 1779043634-279067 X-HE-Meta: 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 X5knF/fh W4F3pJZ7Jg5oSNDemcIkuRoEgf4skqZQUPpoINQvDWv2Nm1pPKFMCIMo2E/DH864AsIqbPaorHvxSFtrQZVoRnr2fB5vYsKnUkGiu+vzaExsC7hv5aq5ln08x6whPLh+QyRYTkohDhu1diTcVYhIX2hIE2gfR3/vzLqtj+CFUSqt7NfF7fJOVeF+5Bq2QctS+/UXAlu812VwblQtz6Ifusdy1o8lh7rGmN45bnBEPNzCcDkLrIW2DmWH3zRiUke3hqdEkc23Worbd3uHS9AfiXqTQThn66iF74HBp1h99+D39iO1L62eDA+p0wQcOEzuP9iVo40hFRX9sJYBiwPFDfG/m0w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 16 May 2026 14:03:55 -0700 Ravi Jonnalagadda wrote: > The CONSIST quota goal tuner initializes esz_bp to 0, producing an > effective quota size (esz) of 1 byte on the first tick. > damos_quota_is_full() rejects all regions when esz < min_region_sz > (default PAGE_SIZE = 4096), so no regions can be tried and no > feedback reaches the tuner — a bootstrapping deadlock. That depend on whether the goal is already [over]-achieved. If the goal is achieved, the tuner will think no change is needed, so keep the effectively-zero quota. If the goal is over-achived, the tuner will think the DAMOS scheme should be less aggressive, but it is already effectively-zero quota, so keep having effectively-zero quota. If the ogal is under-achived, the logic will iteratively increase the internal esz (esz_bp), until it exceeds the min_region_sz, and finally start making some effects. So, unless the goal is already [over]-achieved, there is no deadlock. If the goal is already [over]-achieved, why we would want to make DAMOS do something? Am I missing something? I'd like to discuss this high level thing first, before digging deep into the details. Thanks, SJ [...]