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[90.233.203.182]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54c25bdcc18sm85427e87.72.2025.04.04.03.34.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Apr 2025 03:34:35 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Fri, 4 Apr 2025 12:34:33 +0200 To: Shakeel Butt Cc: Uladzislau Rezki , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] memcg: vmalloc: simplify MEMCG_VMALLOC updates Message-ID: References: <20250403053326.26860-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 33uufbpnikryz7u4xypzznwwk4rxca1i X-Rspam-User: X-Rspamd-Queue-Id: B0426180007 X-Rspamd-Server: rspam08 X-HE-Tag: 1743762878-322207 X-HE-Meta: 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 KxsjjFFQ +orbgoJByqODr59dbkYtzMiR89mS0+Sz/Z28Pl8fcbeBQS58Wc6MUkM0WJFnIelqXbNpJY08HkCXyjGmu6WKLAiy3PKdABMHBGWREq/PGn5DY2WTolAq9SU6kpbYYQ5r6UekLIME8+cLuBYytUtq+kn7+umRpVMMSJ+fNVlB99OPrNpYVl1kZJrahBwthgRl3KQRb17sARa5PxeoGDHTPOkfUVE20dk19/c4D0hEm6I2A//MwEC0InYPY69nzixT8+StzJP7K82cFmVCGH1TwoDZEXal13m6DVLZFN73iXco1lF2z9cm0a4vnfNr1dc8LzpG7EaZV/MTdJbqqiut1wcEA21P5DLW8dhc5vptXb9yzbrkDHBh4W1LjG8SNgmqp2l8x3KNvzTZ9Rpth8LDlEMGlNSG2/cqAQgG6rkwc0/ta/hdpRgw71lqYbwn7273IW1HR 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 Thu, Apr 03, 2025 at 11:20:18AM -0700, Shakeel Butt wrote: > On Thu, Apr 03, 2025 at 01:17:22PM +0200, Uladzislau Rezki wrote: > > On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > > > The vmalloc region can either be charged to a single memcg or none. At > > > the moment kernel traverses all the pages backing the vmalloc region to > > > update the MEMCG_VMALLOC stat. However there is no need to look at all > > > the pages as all those pages will be charged to a single memcg or none. > > > Simplify the MEMCG_VMALLOC update by just looking at the first page of > > > the vmalloc region. > > > > > > Signed-off-by: Shakeel Butt > > > --- > > > mm/vmalloc.c | 13 +++++-------- > > > 1 file changed, 5 insertions(+), 8 deletions(-) > > > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > > index 3ed720a787ec..cdae76994488 100644 > > > --- a/mm/vmalloc.c > > > +++ b/mm/vmalloc.c > > > @@ -3370,12 +3370,12 @@ void vfree(const void *addr) > > > > > > if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) > > > vm_reset_perms(vm); > > > + if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES)) > > > + mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages); > > > > > Could you please add a comment stating that the first page should be > > modified? > > > > Sorry, what do you mean by first page should be modified? > mod_memcg_page_state() will not modify the page but extract memcg from > it and modify its vmalloc stat. > I meant what you wrote in the commit message. A mod_memcg_page_state() can be invoked only on a first page within a mapped range, because the rest is anyway is associated with the same mem_cgroup struct. Just add a comment that we do not need to check all pages. Can you add it? -- Uladzislau Rezki