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Fri, 23 May 2025 13:47:29 +0800 Message-ID: Date: Fri, 23 May 2025 13:47:28 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: fix the inaccurate memory statistics issue for users To: Donet Tom , akpm@linux-foundation.org, david@redhat.com, shakeelb@google.com Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <3dd21f662925c108cfe706c8954e8c201a327550.1747969935.git.baolin.wang@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: k56gm4o3z41bn34xefswumf3ci5bz9cr X-Rspamd-Queue-Id: A885A40002 X-Rspamd-Server: rspam11 X-HE-Tag: 1747979253-415777 X-HE-Meta: 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 NQP9FNGB R7zKQA+pDbYoA9WMgnVbyLN1xUM02DSgc4Ep9i8IZuZwM2YQ77WLs4VNyC/sFwPoGX1vl011KwOehlc6BHqmRRPSbJAhBecvdnRO4v4zvBQ97FQD5bEsjBsbiWUz1hp7pMnrXfq8RI38nuIxLof2+Xbt9KkpIUP+cmHT4/YDh9agiF9h2ipSd79FY8T0dxpBiYW++la20erD/ef9+P4mtVIxPYBN3jD32Kd6z1z5xe1dWEXbypQLxWhotriF7lqrhg5hFEP+XA52/c6fwaCwvUIJ+YGabeavO2q1ZugZeaKn96Jd76xQP9aDcwzNN/mOIWuxesYMniUT1IUJda/b+DSBPF3SZB3vYQu4zgF/QtXYMd8Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/5/23 13:25, Donet Tom wrote: > > On 5/23/25 8:46 AM, Baolin Wang wrote: >> On some large machines with a high number of CPUs running a 64K 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+ COMMAND >>   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 systemd >> >> 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 >> optimized, >> but on some paths, performance may take precedence over statistical >> accuracy. >> 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 >> modification >> should be acceptable. >> >> Signed-off-by: Baolin Wang >> --- >>   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; >> -    anon = get_mm_counter(mm, MM_ANONPAGES); >> -    file = get_mm_counter(mm, MM_FILEPAGES); >> -    shmem = get_mm_counter(mm, MM_SHMEMPAGES); >> +    anon = get_mm_counter_sum(mm, MM_ANONPAGES); > > > Hi Baolin Wang, > > We also observed the same issue where the RSS value in /proc/PID/status > was 0 on machines with a high number of CPUs. With this patch, the issue > got fixedl Yes, we also observed this issue. > Rss value without this patch > ---------------------------- >  # cat /proc/87406/status > ..... > VmRSS:           0 kB > RssAnon:           0 kB > RssFile:           0 k > > > Rss values with this patch > -------------------------- >  # cat /proc/3055/status > VmRSS:        2176 kB > RssAnon:         512 kB > RssFile:        1664 kB > RssShmem:           0 kB > > Tested-by Donet Tom Thanks for testing.