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Fri, 23 May 2025 11:16:23 +0800 From: Baolin Wang To: 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, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH] mm: fix the inaccurate memory statistics issue for users Date: Fri, 23 May 2025 11:16:13 +0800 Message-ID: <3dd21f662925c108cfe706c8954e8c201a327550.1747969935.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 01ADF180017 X-Stat-Signature: nixhap1cqfkndhrn3jugehbr3cda9ki4 X-Rspam-User: X-HE-Tag: 1747970187-68852 X-HE-Meta: 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 JGuSmpTf wd7pHY6fu3HdmptehEf5ZR4bFpn6UQeYHiA6xHjWigNkIiJ3TFSCoEs1L6LXfh0d8N0gakh/iZtptCgMMHaqRnIWet3oHnLUmH4IzC5yv0wpZNf8bXZQgJ1z/2GBqVrOuqiYAEu+MnLJ+gQA1nahxzRvN+hw8X3xN0CXJN5FJgBlSZfNv9vaSsi9UZU6LyymggQRQkLRbsRnt3kuMgr1Ar7fxXgYYaL8R+aUuV6XOfX6jypl3q84CJvt7YJ7QY11uPyS9UBmEkXAWEo8= 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 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); + 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) -- 2.43.5