From nobody Fri Dec 19 16:07:28 2025 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) (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 8AFC1288A5; Sat, 24 May 2025 02:00:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.110 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748052013; cv=none; b=OKpmocpjMjJEAsa+QF9vMaOGNZhdBqK/43RZBMJS5YBGmyIkAPkSf0SmAPLPc1GfMogC3u3mMucbZygMHN+lsAPahWCA4mG62VC2H6b1fT8VvNOHqi8CDBm5oUl6yZYaLHYvhvyukCcbhh256+Nu3T32t68ib6+i+1qSy9u0QZM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748052013; c=relaxed/simple; bh=yVsIs9c2VNbcBMNMt2QKM6J6M2oE1mZDuv/fT2zyWkk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=XBRiF5nFTYnXa8a3Iu8IZ95R7ummyHKtWSs41hzrRmKdZ0mapoLShxuuZfOr4RrbC5MFEuG5FVMO8ECBL+zYXJveskLj5DZLrcO7AXS9K0KGhKVD0TIREFm2TCi14uWgeHRaKrDHnFzMqqRMu0zcZ2kXkCYvev825xrkEuFH38E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=iGM1QGsL; arc=none smtp.client-ip=115.124.30.110 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="iGM1QGsL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1748052007; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=+lI6y2wDJ47d4yiPcvPJikdG0IMfeTY5l5iLcdXaZ4c=; b=iGM1QGsLFrKnaqh43kXkDXkmQ3/cLlmyVkhEkFgRxYMEvdzDG2a7x+JLDllCObjbCfs6ib/qYv3TyM/00MYN0MVwdYyh17HPxD3kn91orMhJSR37X+s5j+pt15cazYQ6kYj5GYaLo+eLNRd3V6FnHZ6ozJanklEMNMuc3w5I2/0= Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WbcNlVP_1748052005 cluster:ay36) by smtp.aliyun-inc.com; Sat, 24 May 2025 10:00:05 +0800 From: Baolin Wang To: akpm@linux-foundation.org, david@redhat.com, shakeel.butt@linux.dev Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, donettom@linux.ibm.com, aboorvad@linux.ibm.com, sj@kernel.org, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm: fix the inaccurate memory statistics issue for users Date: Sat, 24 May 2025 09:59:53 +0800 Message-ID: <4f0fd51eb4f48c1a34226456b7a8b4ebff11bf72.1748051851.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On some large machines with a high number of CPUs running a 64K pagesize kernel, we found that the 'RES' field is always 0 displayed by the top command for some processes, which will cause a lot of confusion for users. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMM= AND 875525 root 20 0 12480 0 0 R 0.3 0.0 0:00.08 top 1 root 20 0 172800 0 0 S 0.0 0.0 0:04.52 syst= emd The main reason is that the batch size of the percpu counter is quite large on these machines, caching a significant percpu value, since converting mm's rss stats into percpu_counter by commit f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter"). Intuitively, the batch number should be optimi= zed, but on some paths, performance may take precedence over statistical accurac= y. Therefore, introducing a new interface to add the percpu statistical count and display it to users, which can remove the confusion. In addition, this change is not expected to be on a performance-critical path, so the modific= ation should be acceptable. Fixes: f1a7941243c1 ("mm: convert mm's rss stats into percpu_counter") Tested-by Donet Tom Reviewed-by: Aboorva Devarajan Tested-by: Aboorva Devarajan Acked-by: Shakeel Butt Acked-by: SeongJae Park Signed-off-by: Baolin Wang Acked-by: Michal Hocko Tested-by Donet Tom --- Changes from RFC: - Collect reviewed and tested tags. Thanks. - Add Fixes tag. --- fs/proc/task_mmu.c | 14 +++++++------- include/linux/mm.h | 5 +++++ 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index b9e4fbbdf6e6..f629e6526935 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -36,9 +36,9 @@ void task_mem(struct seq_file *m, struct mm_struct *mm) unsigned long text, lib, swap, anon, file, shmem; unsigned long hiwater_vm, total_vm, hiwater_rss, total_rss; =20 - anon =3D get_mm_counter(mm, MM_ANONPAGES); - file =3D get_mm_counter(mm, MM_FILEPAGES); - shmem =3D get_mm_counter(mm, MM_SHMEMPAGES); + anon =3D get_mm_counter_sum(mm, MM_ANONPAGES); + file =3D get_mm_counter_sum(mm, MM_FILEPAGES); + shmem =3D get_mm_counter_sum(mm, MM_SHMEMPAGES); =20 /* * Note: to minimize their overhead, mm maintains hiwater_vm and @@ -59,7 +59,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm) text =3D min(text, mm->exec_vm << PAGE_SHIFT); lib =3D (mm->exec_vm << PAGE_SHIFT) - text; =20 - swap =3D get_mm_counter(mm, MM_SWAPENTS); + swap =3D get_mm_counter_sum(mm, MM_SWAPENTS); SEQ_PUT_DEC("VmPeak:\t", hiwater_vm); SEQ_PUT_DEC(" kB\nVmSize:\t", total_vm); SEQ_PUT_DEC(" kB\nVmLck:\t", mm->locked_vm); @@ -92,12 +92,12 @@ unsigned long task_statm(struct mm_struct *mm, unsigned long *shared, unsigned long *text, unsigned long *data, unsigned long *resident) { - *shared =3D get_mm_counter(mm, MM_FILEPAGES) + - get_mm_counter(mm, MM_SHMEMPAGES); + *shared =3D get_mm_counter_sum(mm, MM_FILEPAGES) + + get_mm_counter_sum(mm, MM_SHMEMPAGES); *text =3D (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> PAGE_SHIFT; *data =3D mm->data_vm + mm->stack_vm; - *resident =3D *shared + get_mm_counter(mm, MM_ANONPAGES); + *resident =3D *shared + get_mm_counter_sum(mm, MM_ANONPAGES); return mm->total_vm; } =20 diff --git a/include/linux/mm.h b/include/linux/mm.h index 185424858f23..15ec5cfe9515 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2568,6 +2568,11 @@ static inline unsigned long get_mm_counter(struct mm= _struct *mm, int member) return percpu_counter_read_positive(&mm->rss_stat[member]); } =20 +static inline unsigned long get_mm_counter_sum(struct mm_struct *mm, int m= ember) +{ + return percpu_counter_sum_positive(&mm->rss_stat[member]); +} + void mm_trace_rss_stat(struct mm_struct *mm, int member); =20 static inline void add_mm_counter(struct mm_struct *mm, int member, long v= alue) --=20 2.43.5