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b=OM1HjBnqp7yKkwww+cpXJ8aqdqp+eUcy4iK49H3GIU08V8TgUyd3oRxOpmO3O8oRC 6wjnYLsI9Bx6LVFZHPgKn0zz0G0GFG26iWp8pf7ILhz9XDFM0gr8OX2t1VQqAP9Mc0 YbavpHRreMLlvyYH8HU/R1uKDGbUh8C+cy4Alhbl6HIeVk+Tpolt59aOCJWQfQDuKO HGB+hR0X1pCBR+fJpYGaKn8Ou/MCmw8biSTLsxawn/wBTQwFAlM1c0af4IxzPydOs4 yEK/dQGCVm8PJvMcbW2j3cugiY2bVZasgeei1bg3c3hJQd8aMj9+Bb9cJXWj3BZflD XLvMfUvGBHefQ== From: SJ Park To: Liew Rui Yan Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm/damon: fix damos quota walk-position tracking Date: Tue, 25 Aug 2026 06:54:57 -0700 Message-ID: <20260825135458.64555-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260825124616.5129-1-aethernet65535@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 77A6420009 X-Stat-Signature: 1uydh4x4szabkgcopfx4xgospfsg9mwt X-Rspam-User: X-HE-Tag: 1787666111-470421 X-HE-Meta: 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 SlnhiYcz jb37bg3VtDI+zmbhJLjvGf4zOhShvH3Jd7YHqHgVbCrwMAz/23EWZ4Pkk1D1EhVz2t+XMayTUglTjwa7gavWst5AVr8lcqqaK9PBuet+wwkVAgd5H3fslE2WwIemgpmnXY9KLY0VTPd1C1Mstp3gaL6ugbbONTbcFCJlavWZCfb/EC6chBcXm50VmVdXqWV5uByqpTppcVswqVSjTydhoeOYNVvktCB8BKC4AYk28iN4fc/o= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 25 Aug 2026 20:46:16 +0800 Liew Rui Yan wrote: > DAMOS uses charge_target_from/charge_addr_from to remember how far a > quota-limited walk has progressed. The current implementation has two > problems: > > 1. Once set, the cursor unconditionally skips and resets at the last > region of the tracked target, so the last region can be skipped even > when it has not been processed. I don't fully understand this. Could you please clarify more? Maybe adding a realistic example scenario would be helpful. > > 2. The cursor only advances when the quota becomes full. Regions that > are filtered out do not move the cursor, and the scheme can remain > stuck on the same regions. I don't fully understand this, either. Could you pleae clarify more? > > Fix this by treating the fields as a rotating walk cursor: > > - Advance the cursor for every region walked while a quota is set, > regardless of whether the region is applied or filtered out. > - Remove the unconditional last-region reset. > - Skip regions before the cursor, and rotate to the next valid target > only after the current target has been fully walked. > - Rename charge_{target,addr}_from to walk_{target,addr}_from and > damos_skip_charged_region() to damos_skip_walked_region(). Because I don't understand the problem, I can't understand benefit of this change. Again, more clarification would be helpful. > > Signed-off-by: Liew Rui Yan > --- > include/linux/damon.h | 6 +- > mm/damon/core.c | 156 +++++++++++++++++++++++++++++------------- > 2 files changed, 111 insertions(+), 51 deletions(-) Quite amount of change. I will review the code after the high level understanding is done. Thanks, SJ [...]