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b=PN2TqF7mywsldtZ/1r+qhAFjnHWy5d5K9e9jGU+IoYRUIj3HuzIEbmujFw4NtvAAa 9zB7ARDDYylKUH0hna69orBn5qin2E/UaDci7PATib5CfeZcdiPX4C1ouP8gmEzgiZ bEL0fMJ62GXrGkiViEihf9T3EI7WIYlJxOVM1kq6vzdO+4Xhz4lwxsf6Z5/CP+xkBb w6Xo3K06b0bw2A69f73unc7GtDhOwaVjBAtr72KCU3Whxo2JS3ddEKscgQyBJlxgLe 9M0aQErBMRi4faekAGL8Sl+w0xi7yfXmzw8nsf+dbNyAhxd15oXYDDlR7mi/FEKZhX eBfh0Wm+LGOXg== From: SJ Park To: Aveline Noir Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] DAMON sysfs: failed update clears tried_regions snapshot Date: Thu, 15 Oct 2026 18:26:21 -0700 Message-ID: <20261016012622.114496-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A97E91C000B X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: pcu3rx4wa39d1ccamx5sijkui4exf98t X-HE-Tag: 1792113990-16135 X-HE-Meta: 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 6ljsU265 y6+uQX6/mZwsGJLd4RVFRDRTDOXcKuMbzQp5LXl/1e1F+JOKyCYgaYbxtLgH9KzTtZeYkxatOVTNoENepyzgNQQNstCKnq4GSuXtW17WotP3TOmz0lKii4SRW1kXBeID+6mjwmts4ZmYAdQPhu7AHzIkiYXV0rJcM9e9tAvVC/CIvlHSWIc9S9P8ajzDGcvAA6kztWbl7aVY/VociZXe9t43XPODywdHMFtcCdBpuo0Mx/BMKdcyMLczCaepGs2+8kDZk9jDvgecTpMbUl2nHe3oxMZ0zcc5LLoHuMKa6/eMmTb/nUOa69HQ9fRvj6Xo7/qg2 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Aveline, Please do not "top-post" [1]. On Thu, 15 Oct 2026 10:17:05 -0500 Aveline Noir wrote: > Hi SJ, > > I haven't seen this affect a real workload. I found it while testing > the DAMON sysfs interface. You shared 4 bug reports in very short time. Three of those are from 32 bit. Could you disclose the purpose of the testing and how you are doing the testing, finding bugs, and reporting those? > > If a tool tries to refresh after monitoring stops, the failed request > can delete the last snapshot. The tool then has no previous result to > fall back to. Why would the tool tries to refresh the regions after the monitoring is stopped? > > I built and tested 66178e4ec30a and its parent cce0b334c310 with the > same config and reproducer. In three runs each, the parent kept the > 4 MiB snapshot after rejecting the refresh; 66178e4ec30a cleared it. > Both returned -EINVAL. Is this an answer to my bisection question? [1] https://subspace.kernel.org/etiquette.html#do-not-top-post-when-replying Thanks, SJ [...]