From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) (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 C74A2212D86; Mon, 1 Jun 2026 02:33:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780281240; cv=none; b=PTg1OszUn+tP0g9rVGgWf8mHrhalQrIe+AOBSr7Jwb4qGor6MKfan5VG8ifPRAe51biCcnNBz+Ny07jd6MHzJyjKoKmcBGi62RQqS/eBZJMOFvUjbU3pj5vh6kPthUg2UHE4ORT5N4J4MzIqOowLGwryiH9A3IEe1d3pm3E2ucU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780281240; c=relaxed/simple; bh=JqDHJVAKyGpl+ngYGBc4rz9MtrD0LjNaznhwCYkd3R8=; h=MIME-Version:Date:Content-Type:From:Message-ID:Subject:To:Cc: In-Reply-To:References; b=MYtZowmUPhGpxmOgU56TXmuOcuOOYWZVkazCDX4RNAz5BBQUYRIDkVKscnNxzGdZlz02uvZuQnmOcIYuDUnyVhgS99uVNCiz3zzVmyfVcAB9W3QetA1x6Vu+zOiiAh/f/twl/XWUWJivxkkMFqD8RMQ48X++z2TU9AQjwj6vOnE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=USGIKcbS; arc=none smtp.client-ip=95.215.58.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="USGIKcbS" Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780281236; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TMHgRM2VgLCMfYV/Kx1tsJefCoHRzu2kO6ZVF0TG+Ng=; b=USGIKcbS9nOCEqYdBNcQ0LJXZKLix/4zkNsDQi4I/bTsjwkJ15Jjc1l9ouC84+s+uKAKQx peltIFP+3sBipJu0MValVmndBCloOGVXp684I5NEdj9O7B438dTOT+Xa87xcFq25H6G3bX eOWzpOa7XvD1Dae3zeJmayev2iA3IrQ= Date: Mon, 01 Jun 2026 02:33:50 +0000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: "Kunwu Chan" Message-ID: <4915dbdd42711403f1781e3c7a71a11a53b0249d@linux.dev> TLS-Required: No Subject: Re: [PATCH 4/5] selftests/damon/damos_tried_regions: handle empty tried regions in early cycles To: "SeongJae Park" Cc: "SeongJae Park" , shuah@kernel.org, damon@lists.linux.dev, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kunwu Chan" , "Wang Lian" , "Kunwu Chan" In-Reply-To: <20260531165437.99410-1-sj@kernel.org> References: <20260531165437.99410-1-sj@kernel.org> X-Migadu-Flow: FLOW_OUT June 1, 2026 at 12:54 AM, "SeongJae Park" wrote: >=20 >=20On Sun, 31 May 2026 17:17:23 +0800 Kunwu Chan = wrote: >=20 >=20>=20 >=20> From: Kunwu Chan > >=20=20 >=20> The test aborts if the initial aggregation cycles produce zero > > tried regions. This can happen on slow machines, causing false > > failures. Skip empty cycles and retry up to 200 times before > > giving up. Also check that enough samples were collected before > > computing the 50th percentile. > >=20 >=20I agree this will make the test be more reliable. I'm bit concerned i= f 200 > times retry can make the test run too long, though. >=20 >=20Also, could you further elaborate why this can fail on slow machines?= That is, > DAMON will check the access of 'access_memory_even' process every 5ms. = Are you > thinking the 5ms is too short for 'access_memory_event' to make the exp= ected > access (accessing the 7 regins of 10 MiB size) within? If so, should we > increase the sampling interval before retrying? >=20 >=20I also suspect if the unreliable results you seen is due to the fact = that DAMON > is not flushing TLB, like we discussed before. If that's the case, coul= d we > increase the working set size of this test, similar to the wss_estimati= on test? >=20 Thanks,=20SJ. Good points. I don't yet have enough evidence to say whether this is primarily due to scheduling delays, a too-short sampling interval, or effects from not flushing TLB. I'll investigate the root cause and see if increasing the working set size or adjusting the test configuration may be a cleaner solution than adding retries. I'll drop this patch from v2 for now and revisit it once I better understand the root cause. Thanks, Kunwu > [1] https://lore.kernel.org/20260525144846.604907-1-kunwu.chan@linux.de= v >=20 >=20Thanks, > SJ >=20 >=20[...] >