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 9EA9D274B30; Fri, 31 Oct 2025 03:29:53 +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=1761881393; cv=none; b=iozhhCNYaLbxV8Q4LP0rAZ22ZPPOC6aNXRwC1bD/1fwFapQtI7ouGqZS3xIO6pxQ08xINlM12E1N+atH5yeuO53djCT/xy3JngMZuSBC8dhooUz3pqJKyG9bFT/7jtvov6a0oUnFWDAPYMbAVxYVszH3WGa2gwSRzX6Ilwkjjys= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761881393; c=relaxed/simple; bh=tOp+KRVH2sLltKtt6CMWxaH3Av4wegBgKUKCf/CTyEo=; h=Date:To:From:Subject:Message-Id; b=Qr/y/lZeJ4APpuUPHWKDhR3QwunSbfFi4cNXMoHTgtSMP8JMh8g5OXGX451waElaepA0r/+K4qfhpbKULPrMNhvE1kqOtX0JJl6uD9hXZg/B7zo+0SbwJF4yxvY1fPvdyJfIZn2swhkKhtgKeg568ZTI0WtKLSR1OkoZebJPQDo= 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=CkMI+lT5; 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="CkMI+lT5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 232E8C113D0; Fri, 31 Oct 2025 03:29:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1761881393; bh=tOp+KRVH2sLltKtt6CMWxaH3Av4wegBgKUKCf/CTyEo=; h=Date:To:From:Subject:From; b=CkMI+lT5dKKfziI8gEoCOIod4BnOdLS6EuZdg4v0hwQ0INQsjScz5+JUfkHl+YyyW 28NuUGgzOsLmseXmgXOzCo2ISqSqwwgQN6y3LAdWuN/STEXyWAU+Z71QNHNKY2gbZZ IK9OVV42BW2J7PhjFgdmQ/4NcTRZ0g0ApZpVTtAM= Date: Thu, 30 Oct 2025 20:29:52 -0700 To: mm-commits@vger.kernel.org,zuoze1@huawei.com,wangkefeng.wang@huawei.com,stable@vger.kernel.org,sj@kernel.org,yanquanmin1@huawei.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-damon-sysfs-change-next_update_jiffies-to-a-global-variable.patch added to mm-hotfixes-unstable branch Message-Id: <20251031032953.232E8C113D0@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/damon/sysfs: change next_update_jiffies to a global variable has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-sysfs-change-next_update_jiffies-to-a-global-variable.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-sysfs-change-next_update_jiffies-to-a-global-variable.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 the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Quanmin Yan Subject: mm/damon/sysfs: change next_update_jiffies to a global variable Date: Thu, 30 Oct 2025 10:07:46 +0800 In DAMON's damon_sysfs_repeat_call_fn(), time_before() is used to compare the current jiffies with next_update_jiffies to determine whether to update the sysfs files at this moment. On 32-bit systems, the kernel initializes jiffies to "-5 minutes" to make jiffies wrap bugs appear earlier. However, this causes time_before() in damon_sysfs_repeat_call_fn() to unexpectedly return true during the first 5 minutes after boot on 32-bit systems (see [1] for more explanation, which fixes another jiffies-related issue before). As a result, DAMON does not update sysfs files during that period. There is also an issue unrelated to the system's word size[2]: if the user stops DAMON just after next_update_jiffies is updated and restarts it after 'refresh_ms' or a longer delay, next_update_jiffies will retain an older value, causing time_before() to return false and the update to happen earlier than expected. Fix these issues by making next_update_jiffies a global variable and initializing it each time DAMON is started. Link: https://lkml.kernel.org/r/20251030020746.967174-3-yanquanmin1@huawei.com Link: https://lkml.kernel.org/r/20250822025057.1740854-1-ekffu200098@gmail.com [1] Link: https://lore.kernel.org/all/20251029013038.66625-1-sj@kernel.org/ [2] Fixes: d809a7c64ba8 ("mm/damon/sysfs: implement refresh_ms file internal work") Suggested-by: SeongJae Park Reviewed-by: SeongJae Park Signed-off-by: Quanmin Yan Cc: Kefeng Wang Cc: ze zuo Cc: Signed-off-by: Andrew Morton --- mm/damon/sysfs.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/mm/damon/sysfs.c~mm-damon-sysfs-change-next_update_jiffies-to-a-global-variable +++ a/mm/damon/sysfs.c @@ -1552,16 +1552,17 @@ static struct damon_ctx *damon_sysfs_bui return ctx; } +static unsigned long damon_sysfs_next_update_jiffies; + static int damon_sysfs_repeat_call_fn(void *data) { struct damon_sysfs_kdamond *sysfs_kdamond = data; - static unsigned long next_update_jiffies; if (!sysfs_kdamond->refresh_ms) return 0; - if (time_before(jiffies, next_update_jiffies)) + if (time_before(jiffies, damon_sysfs_next_update_jiffies)) return 0; - next_update_jiffies = jiffies + + damon_sysfs_next_update_jiffies = jiffies + msecs_to_jiffies(sysfs_kdamond->refresh_ms); if (!mutex_trylock(&damon_sysfs_lock)) @@ -1607,6 +1608,9 @@ static int damon_sysfs_turn_damon_on(str } kdamond->damon_ctx = ctx; + damon_sysfs_next_update_jiffies = + jiffies + msecs_to_jiffies(kdamond->refresh_ms); + repeat_call_control->fn = damon_sysfs_repeat_call_fn; repeat_call_control->data = kdamond; repeat_call_control->repeat = true; _ Patches currently in -mm which might be from yanquanmin1@huawei.com are mm-damon-stat-change-last_refresh_jiffies-to-a-global-variable.patch mm-damon-sysfs-change-next_update_jiffies-to-a-global-variable.patch mm-damon-add-a-min_sz_region-parameter-to-damon_set_region_biggest_system_ram_default.patch mm-damon-reclaim-use-min_sz_region-for-core-address-alignment-when-setting-regions.patch