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 2E2122032D; Tue, 7 Apr 2026 22:29:38 +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=1775600978; cv=none; b=a0nMHkS5Jw/1Px4EIpLSsWK51mLPsksXg10HT09uHa0CL3FfNPNV8adc4btgNm9UsBBqg+wgGuUAujNgyjQutipG/VTFBh4yejo4okGzLuIP6dI++DvQihFWxz1N/DgWz0KptqwS0m6yBFQ7rdv4z4qK1eOhxbhiE5Kwj6N+g8A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775600978; c=relaxed/simple; bh=iqXAjr3qnlsFqWkeSXVmcP16oOYMJl2pQ64LH+NoKjw=; h=Date:To:From:Subject:Message-Id; b=i6c6RSLoEq7KpLuRFbT45eVHKTon0CRVFWue1LqyxUfb87GA6mfkHW6nX5YjbpVOjt8XTROQ33eM2uZXWCtag9kUq8clSLDHMDDlQT80Tara7LrzKSnnsLrS2InxCssBfOOgzOdTPpL002J65PsUfQx750IlRPRCVvLDfbCtMAY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=oSMISXXX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="oSMISXXX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0943C116C6; Tue, 7 Apr 2026 22:29:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1775600978; bh=iqXAjr3qnlsFqWkeSXVmcP16oOYMJl2pQ64LH+NoKjw=; h=Date:To:From:Subject:From; b=oSMISXXX7QGtfgUOaJ4BqDyLlJGp9bh6uAdzC8XSV5dQFOv23g8hZryjx/Piv3ZRA yJNxTUmxnHBNfPPFi2E4tanKOijqSlYSDb4WljraYa+8Xln99RCliBYqihE1S0Aed0 zv6I+ZMhIFbJdpmUrjcpguElDz/IKyetHl9K/1qE= Date: Tue, 07 Apr 2026 15:29:37 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sj@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-damon-core-disallow-time-quota-setting-zero-esz.patch added to mm-hotfixes-unstable branch Message-Id: <20260407222937.F0943C116C6@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/damon/core: disallow time-quota setting zero esz has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-core-disallow-time-quota-setting-zero-esz.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-disallow-time-quota-setting-zero-esz.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: SeongJae Park Subject: mm/damon/core: disallow time-quota setting zero esz Date: Mon, 6 Apr 2026 17:31:52 -0700 When the throughput of a DAMOS scheme is very slow, DAMOS time quota can make the effective size quota smaller than damon_ctx->min_region_sz. In the case, damos_apply_scheme() will skip applying the action, because the action is tried at region level, which requires >=min_region_sz size. That is, the quota is effectively exceeded for the quota charge window. Because no action will be applied, the total_charged_sz and total_charged_ns are also not updated. damos_set_effective_quota() will try to update the effective size quota before starting the next charge window. However, because the total_charged_sz and total_charged_ns have not updated, the throughput and effective size quota are also not changed. Since effective size quota can only be decreased, other effective size quota update factors including DAMOS quota goals and size quota cannot make any change, either. As a result, the scheme is unexpectedly deactivated until the user notices and mitigates the situation. The users can mitigate this situation by changing the time quota online or re-install the scheme. While the mitigation is somewhat straightforward, finding the situation would be challenging, because DAMON is not providing good observabilities for that. Even if such observability is provided, doing the additional monitoring and the mitigation is somewhat cumbersome and not aligned to the intention of the time quota. The time quota was intended to help reduce the user's administration overhead. Fix the problem by setting time quota-modified effective size quota be at least min_region_sz always. The issue was discovered [1] by sashiko. Link: https://lkml.kernel.org/r/20260407003153.79589-1-sj@kernel.org Link: https://lore.kernel.org/20260405192504.110014-1-sj@kernel.org [1] Fixes: 1cd243030059 ("mm/damon/schemes: implement time quota") Signed-off-by: SeongJae Park Cc: # 5.16.x Signed-off-by: Andrew Morton --- mm/damon/core.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/mm/damon/core.c~mm-damon-core-disallow-time-quota-setting-zero-esz +++ a/mm/damon/core.c @@ -2228,7 +2228,8 @@ static unsigned long damos_quota_score(s /* * Called only if quota->ms, or quota->sz are set, or quota->goals is not empty */ -static void damos_set_effective_quota(struct damos_quota *quota) +static void damos_set_effective_quota(struct damos_quota *quota, + struct damon_ctx *ctx) { unsigned long throughput; unsigned long esz = ULONG_MAX; @@ -2254,6 +2255,7 @@ static void damos_set_effective_quota(st else throughput = PAGE_SIZE * 1024; esz = min(throughput * quota->ms, esz); + esz = max(ctx->min_region_sz, esz); } if (quota->sz && quota->sz < esz) @@ -2290,7 +2292,7 @@ static void damos_adjust_quota(struct da /* First charge window */ if (!quota->total_charged_sz && !quota->charged_from) { quota->charged_from = jiffies; - damos_set_effective_quota(quota); + damos_set_effective_quota(quota, c); } /* New charge window starts */ @@ -2303,7 +2305,7 @@ static void damos_adjust_quota(struct da quota->charged_sz = 0; if (trace_damos_esz_enabled()) cached_esz = quota->esz; - damos_set_effective_quota(quota); + damos_set_effective_quota(quota, c); if (trace_damos_esz_enabled() && quota->esz != cached_esz) damos_trace_esz(c, s, quota); } _ Patches currently in -mm which might be from sj@kernel.org are mm-damon-core-disallow-time-quota-setting-zero-esz.patch mm-damon-core-fix-damon_call-vs-kdamond_fn-exit-race.patch mm-damon-core-fix-damos_walk-vs-kdamond_fn-exit-race.patch mm-damon-core-validate-damos_quota_goal-nid-for-node_mem_usedfree_bp.patch mm-damon-core-validate-damos_quota_goal-nid-for-node_memcg_usedfree_bp.patch mm-damon-core-use-time_in_range_open-for-damos-quota-window-start.patch docs-admin-guide-mm-damon-reclaim-warn-commit_inputs-vs-param-updates-race.patch docs-admin-guide-mm-damon-lru_sort-warn-commit_inputs-vs-param-updates-race.patch