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Fri, 23 May 2025 05:25:31 GMT Received: from smtpav01.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E042058055; Fri, 23 May 2025 05:25:30 +0000 (GMT) Received: from smtpav01.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7ED4E5804B; Fri, 23 May 2025 05:25:26 +0000 (GMT) Received: from [9.109.245.113] (unknown [9.109.245.113]) by smtpav01.wdc07v.mail.ibm.com (Postfix) with ESMTP; Fri, 23 May 2025 05:25:26 +0000 (GMT) Message-ID: Date: Fri, 23 May 2025 10:55:24 +0530 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: fix the inaccurate memory statistics issue for users To: Baolin Wang , 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> Content-Language: en-US From: Donet Tom In-Reply-To: <3dd21f662925c108cfe706c8954e8c201a327550.1747969935.git.baolin.wang@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTIzMDA0MyBTYWx0ZWRfXxJRyzXsBHwPu ntI7I4Tfrkndp3EDwoJkzFtMFt1SrDrd4/OJZbkVsyFNhyXBqlWt5T60KgrRAvArIWyqbdojjLG xvVJUJdNJdVIVGHCaSNTyc3xl5x+5u23R45UgqRABKUzT59mII6631AnypDu8ziqwC5K08Awuvg 6VpjHGcEG5Nmk1IRHV0xxuUMKApIVjqUQRxFaNUlnQuLz0ZmMU/X/hAwOKKSdKQWZ39Ygr8cKpH CSC1/iQEsdSZY89LbM1fYr2duU2XX4nj7/TRtaArr0AqZSd7zjIpZjtv+bEF1wQXTM88xCd9Y4t HedN3azxspFzNXi9Tj710bHdKQOOWBZvi1PrvwPMpfDp4w+BDdrFPtOMg7EbWSYZqXWKWRkrDcm JJa8uz8xYd+Fp7cJDie6iAnYKNvPzhzQXWP2AJIBzYYxyRXBvlQPOJ+6cJnHrLC7pNaZMH5g X-Proofpoint-GUID: Fc8I8pRSBtQX3eEirUu-2IZEmgh7OJaG X-Authority-Analysis: v=2.4 cv=O685vA9W c=1 sm=1 tr=0 ts=683006cd cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=SRrdq9N9AAAA:8 a=VnNF1IyMAAAA:8 a=bJgjvqlET6HPnKk_xIcA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: LM8uU1SdoVM6B511od_tFrYjKP9VKcpO X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-23_02,2025-05-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxlogscore=999 spamscore=0 mlxscore=0 phishscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 clxscore=1011 malwarescore=0 suspectscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505160000 definitions=main-2505230043 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 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 > + file = get_mm_counter_sum(mm, MM_FILEPAGES); > + shmem = get_mm_counter_sum(mm, MM_SHMEMPAGES); > > /* > * 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 = min(text, mm->exec_vm << PAGE_SHIFT); > lib = (mm->exec_vm << PAGE_SHIFT) - text; > > - swap = get_mm_counter(mm, MM_SWAPENTS); > + swap = 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 = get_mm_counter(mm, MM_FILEPAGES) + > - get_mm_counter(mm, MM_SHMEMPAGES); > + *shared = get_mm_counter_sum(mm, MM_FILEPAGES) + > + get_mm_counter_sum(mm, MM_SHMEMPAGES); > *text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) > >> PAGE_SHIFT; > *data = mm->data_vm + mm->stack_vm; > - *resident = *shared + get_mm_counter(mm, MM_ANONPAGES); > + *resident = *shared + get_mm_counter_sum(mm, MM_ANONPAGES); > return mm->total_vm; > } > > 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]); > } > > +static inline unsigned long get_mm_counter_sum(struct mm_struct *mm, int member) > +{ > + return percpu_counter_sum_positive(&mm->rss_stat[member]); > +} > + > void mm_trace_rss_stat(struct mm_struct *mm, int member); > > static inline void add_mm_counter(struct mm_struct *mm, int member, long value)