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From: Yosry Ahmed To: Shakeel Butt Cc: Andrew Morton , Uladzislau Rezki , 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: <20250403053326.26860-1-shakeel.butt@linux.dev> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 2C86210000F X-Stat-Signature: hoafmtktfe8ccnpby1wgi9au69d183wb X-Rspam-User: X-HE-Tag: 1745335068-964346 X-HE-Meta: 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 kAZiWOQR H9bJ4kCo8iQh5bawU/lGRR2VCqPDzAqghWhrEt6ifvM1d5eWjzYwAaXvUB9/rwGl5L8DzmR1bpwLh5LHnidCvfLVIzyB/1xRCwn+fkgmZ1HrOjd6aCx/jvYwW7DXFR4QXO2vQwqOxrCsf5v8d3MNu6PkfIG1P76a2N7thzR6oU2AZKlohY9pmnNeEBltEIsAXXOB3FNDEPi4W8+fx84Rr8zQszjkESpZQHO1RGv+XPb8SdS8= 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 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); > for (i = 0; i < vm->nr_pages; i++) { > struct page *page = vm->pages[i]; > > BUG_ON(!page); > - if (!(vm->flags & VM_MAP_PUT_PAGES)) > - mod_memcg_page_state(page, MEMCG_VMALLOC, -1); We can add a debug check here (and/or in the vmalloc path) to check that all pages are indeed charged to the same memcg. Regardless, this change makes sense: Reviewed-by: Yosry Ahmed > /* > * High-order allocs for huge vmallocs are split, so > * can be freed as an array of order-0 allocations > @@ -3671,12 +3671,9 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > node, page_order, nr_small_pages, area->pages); > > atomic_long_add(area->nr_pages, &nr_vmalloc_pages); > - if (gfp_mask & __GFP_ACCOUNT) { > - int i; > - > - for (i = 0; i < area->nr_pages; i++) > - mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC, 1); > - } > + if (gfp_mask & __GFP_ACCOUNT && area->nr_pages) > + mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC, > + area->nr_pages); > > /* > * If not enough pages were obtained to accomplish an > -- > 2.47.1 > >