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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 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9A03A140010 X-Stat-Signature: s5drnog5mzp3fgcoziac5becoucy5mcx X-Rspam-User: X-HE-Tag: 1748052010-352228 X-HE-Meta: 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 PEAZT/pz /5TyJnsRCaZffXvRSxmntAE5+Ko4aLBk4o0+mlfo0H505xyhLLxy23Ew68opIl72W9no5TZwOQp9dU/zs3tyxuOR19srnE03s90NfW8v33ohVEkX+IWJr/7poiYCmmR3IIfEag89U+RZMDE0J7S9PEOeYA2pJ8C/Bpawa8C0tiyTTC6wURR52wcWmGIOSo1b8dxQm0XNoLid/LcS0oDl0RGEL/21J2adrKT5fkjNqcy5O0zmntdE+iQgfLFSvc4ugfMuaYGqn2/iO3Mylp+n1H7bIN8sk2BLagbcOZtpuuaG8YTcNTgPepCrhfg== 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 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+ 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. 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 --- 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; - 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