From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4272140DFB2; Sat, 21 Mar 2026 01:02:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774054926; cv=none; b=iCpFidn+bwJpLe+bo5joAU589DVmMPrUq76mNtZK+u5gBNLf1o6AnGpusefqytpdh2ClDqOTKekQnhQgHG7uviGDL1e4MwJcppPwuWUvHNsQT3SIwsQKbClzgVOZ84ZjccErArGoq4p+JOXyJ1NLgAk0gSYSpaNw1R5XJS1CaGY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774054926; c=relaxed/simple; bh=0yYB8TFfBq7hSyyiDU6/wS7/MxpcVDUgHb7ZxIWACZA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TMNnX82WFXaApxAD3PtBhpKSGsnrWv95KA8d4aNBl69/r+PGAeJ7ypUDBb745hBe2PSnl5p6/uIDRQh9MM1eESphiW6gAzJp5IuiH5UuK37iWz+dG212Vbgp8LPjdB49vkGuI9MGkwsNpLLSJ3ikLx5gfriOQBKbAcXZZ/hCyyE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DMpMpIhY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DMpMpIhY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3DC03C4CEF7; Sat, 21 Mar 2026 01:02:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774054925; bh=0yYB8TFfBq7hSyyiDU6/wS7/MxpcVDUgHb7ZxIWACZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DMpMpIhY+oJin9kFaNMgEx8u1rCcFnwjvNXXicnucVhUrhHq92rJfctXXDBpMFS6N wiiKMbngcuEeCcNZIkz76p5WAgzgjnlKFdoG6Jw1qxKegJDCq431XVWWrkml2BJP8t YAuf+cCK/e1U2bd1CLuyIiB8dmtjHSHIcl8Xiw4F/Izdv3v+63VoRFvgR918XTieVu /elS6A9JwPTFaHxiQYSq/azAydQg1+N3Of8aLJSibOISuGAYKPtvi29QJe3MYev0S1 czivg0DIhShYu/K9QgeDXNQDUiFAYVCA49XubWxPrZhRUyvBTX8hk1N2jDg3rnuA9l jkwiy35UJdR2A== From: SeongJae Park To: SeongJae Park Cc: Shuah Khan , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v2 10/10] selftets/damon/sysfs.py: pause DAMON before dumping status Date: Fri, 20 Mar 2026 18:02:00 -0700 Message-ID: <20260321010201.82092-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260320154134.99740-1-sj@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Fri, 20 Mar 2026 08:41:33 -0700 SeongJae Park wrote: > On Fri, 20 Mar 2026 08:29:39 -0700 SeongJae Park wrote: > > > Adding Sashiko comment > > (https://lore.kernel.org/https://sashiko.dev/#/patchset/20260319052157.99433-11-sj@kernel.org) > > with ': ' line prefix, and my replies in line. > > > > On Wed, 18 Mar 2026 22:21:53 -0700 SeongJae Park wrote: > > > > > The sysfs.py test commits DAMON parameters, dump the internal DAMON > > > state, and show if the parameters are committed as expected using the > > > dumped state. While the dumping is ongoing, DAMON is alive. It can > > > make internal changes including addition and removal of regions. It can > > > therefore make a race that can result in false test results. Pause > > > DAMON execution during the state dumping to avoid such races. > > > > > > Signed-off-by: SeongJae Park > > > --- > > > tools/testing/selftests/damon/sysfs.py | 31 ++++++++++++++++++++++++++ > > > 1 file changed, 31 insertions(+) > > > > > > diff --git a/tools/testing/selftests/damon/sysfs.py b/tools/testing/selftests/damon/sysfs.py > > > index e6d34ba05893f..704729c7a318e 100755 > > > --- a/tools/testing/selftests/damon/sysfs.py > > > +++ b/tools/testing/selftests/damon/sysfs.py > > > @@ -193,18 +193,48 @@ def assert_ctx_committed(ctx, dump): > > > assert_true(dump['pause'] == ctx.pause, 'pause', dump) > > > > > > def assert_ctxs_committed(kdamonds): > > > + ctxs_paused_for_dump = [] > > > + for kd in kdamonds.kdamonds: > > > + for ctx in kd.contexts: > > > + if ctx.pause is False: > > > + ctx.pause = True > > > + err = kd.commit() > > > + if err is not None: > > > + print('pause fail (%s)' % err) > > > + kdamonds.stop() > > > + exit(1) > > > + ctxs_paused_for_dump.append(ctx) > > > + > > > status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid) > > > if err is not None: > > > print(err) > > > kdamonds.stop() > > > exit(1) > > > > > > + for kd in kdamonds.kdamonds: > > > + for ctx in kd.contexts: > > > + if ctx in ctxs_paused_for_dump: > > > + ctx.pause = False > > > + err = kd.commit() > > > + if err is not None: > > > + print('resume fail (%s)' % err) > > > + kdamonds.stop() > > > + exit(1) > > > + # restore for comparison > > > + ctx.pause = True > > > > : If a kdamond contains multiple contexts, does this loop leave earlier contexts > > : paused in the kernel? > > : > > : Since kd.commit() stages and commits the state of all contexts associated with > > : the kdamond, when kd.commit() is called for the second context, the first > > : context's local pause attribute is already back to True. > > : > > : This would cause kd.commit() to write to sysfs and instruct the kernel to > > : pause the first context again. By the end of this loop, only the last context > > : in the kdamond would remain unpaused in the kernel. > > > > No. The pause field of the earlier context is set to False, so later > > kd.commit() will commit the False 'pause' again. But this finds a good point. > > There is no reason to call kd.commit() for each context. It is more efficient > > to be called for each kdamond., thouth currently we support only one context > > per kdamond. I will update the code so, in the next spin. > > I'm wrong, Sashiko is correct. I missed the last 'ctx.pause = True' in the > loop. I will fix this together, like below: > > ''' > --- a/tools/testing/selftests/damon/sysfs.py > +++ b/tools/testing/selftests/damon/sysfs.py > @@ -201,16 +201,17 @@ def assert_ctx_committed(ctx, dump): > > def assert_ctxs_committed(kdamonds): > ctxs_paused_for_dump = [] > + # pause for safe state dumping > for kd in kdamonds.kdamonds: > for ctx in kd.contexts: > if ctx.pause is False: > ctx.pause = True > - err = kd.commit() > - if err is not None: > - print('pause fail (%s)' % err) > - kdamonds.stop() > - exit(1) > ctxs_paused_for_dump.append(ctx) > + err = kd.commit() > + if err is not None: > + print('pause fail (%s)' % err) > + kdamonds.stop() > + exit(1) > > status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid) > if err is not None: > @@ -218,17 +219,19 @@ def assert_ctxs_committed(kdamonds): > kdamonds.stop() > exit(1) > > + # resume contexts paused for safe state dumping > for kd in kdamonds.kdamonds: > - for ctx in kd.contexts: > - if ctx in ctxs_paused_for_dump: > - ctx.pause = False > - err = kd.commit() > - if err is not None: > - print('resume fail (%s)' % err) > - kdamonds.stop() > - exit(1) > - # restore for comparison > - ctx.pause = True > + for ctx in ctxs_paused_for_dump: > + ctx.pause = False > + err = kd.commit() > + if err is not None: > + print('resume fail (%s)' % err) > + kdamonds.stop() > + exit(1) > + > + # restore for comparison > + for ctx in ctxs_paused_for_dump: > + ctx.pause = True > > ctxs = kdamonds.kdamonds[0].contexts > dump = status['contexts'] > ''' The above fixup makes the test fails, for the obsolete targets. The fixup needs another fixup, like below. I will add that to the next spin. ''' --- a/tools/testing/selftests/damon/sysfs.py +++ b/tools/testing/selftests/damon/sysfs.py @@ -200,11 +200,12 @@ def assert_ctxs_committed(kdamonds): if ctx.pause is False: ctx.pause = True ctxs_paused_for_dump.append(ctx) - err = kd.commit() - if err is not None: - print('pause fail (%s)' % err) - kdamonds.stop() - exit(1) + if len(ctxs_paused_for_dump) > 0: + err = kd.commit() + if err is not None: + print('pause fail (%s)' % err) + kdamonds.stop() + exit(1) status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid) if err is not None: @@ -216,11 +217,12 @@ def assert_ctxs_committed(kdamonds): for kd in kdamonds.kdamonds: for ctx in ctxs_paused_for_dump: ctx.pause = False - err = kd.commit() - if err is not None: - print('resume fail (%s)' % err) - kdamonds.stop() - exit(1) + if len(ctxs_paused_for_dump) > 0: + err = kd.commit() + if err is not None: + print('resume fail (%s)' % err) + kdamonds.stop() + exit(1) # restore for comparison for ctx in ctxs_paused_for_dump: ''' Thanks, SJ