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Wed, 25 May 2022 03:29:19 -0700 (PDT) Date: Wed, 25 May 2022 18:29:14 +0800 From: Muchun Song To: Vlastimil Babka Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, smuchun@gmail.com Subject: Re: [PATCH v2] mm: slab: optimize memcg_slab_free_hook() Message-ID: References: <20220429123044.37885-1-songmuchun@bytedance.com> <86fdbde5-a010-9473-2f5d-807c86620509@suse.cz> <970bbb88-3fc7-d2b9-6bb5-9c315888a889@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <970bbb88-3fc7-d2b9-6bb5-9c315888a889@suse.cz> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E58D740033 X-Rspam-User: Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=xtA2d4yq; spf=pass (imf17.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.215.174 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Stat-Signature: iibggbtjp8nzoeobm694octooqcjwd61 X-HE-Tag: 1653474530-282945 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: On Wed, May 25, 2022 at 12:09:19PM +0200, Vlastimil Babka wrote: > On 5/25/22 11:15, Muchun Song wrote: > > On Wed, May 25, 2022 at 09:34:58AM +0200, Vlastimil Babka wrote: > >> On 5/25/22 04:18, Muchun Song wrote: > >> > On Tue, May 24, 2022 at 07:05:31PM +0200, Vlastimil Babka wrote: > >> >> On 4/29/22 14:30, Muchun Song wrote: > >> >> > Most callers of memcg_slab_free_hook() already know the slab, which could > >> >> > be passed to memcg_slab_free_hook() directly to reduce the overhead of an > >> >> > another call of virt_to_slab(). For bulk freeing of objects, the call of > >> >> > slab_objcgs() in the loop in memcg_slab_free_hook() is redundant as well. > >> >> > Rework memcg_slab_free_hook() and build_detached_freelist() to reduce > >> >> > those unnecessary overhead and make memcg_slab_free_hook() can handle bulk > >> >> > freeing in slab_free(). > >> >> > > >> >> > Move the calling site of memcg_slab_free_hook() from do_slab_free() to > >> >> > slab_free() for slub to make the code clearer since the logic is weird > >> >> > (e.g. the caller need to judge whether it needs to call > >> >> > memcg_slab_free_hook()). It is easy to make mistakes like missing calling > >> >> > of memcg_slab_free_hook() like fixes of: > >> >> > > >> >> > commit d1b2cf6cb84a ("mm: memcg/slab: uncharge during kmem_cache_free_bulk()") > >> >> > commit ae085d7f9365 ("mm: kfence: fix missing objcg housekeeping for SLAB") > >> >> > >> >> Hm is this commit also fixing such bug? in mm/slab.c __cache_free(): > >> >> > > > > Sorry, I think I have misread it and misled you here. I mean commit > > My bad, I should have said "this patch" referring to yours, not "this > commit" which could refer to ae085d7f9365. > > > ae085d7f9365 ("mm: kfence: fix missing objcg housekeeping for SLAB") > > is a bug fix, this commit does not fix any issue since __cache_free() > > will be called from qlink_free() and __cache_free() will call > > memcg_slab_free_hook(), so there is no issues. This commit is totally > > an improvements for memcg_slab_free_hook(). > > Ah, I see, indeed. The un-quarantining in kasan went through > memcg_slab_free_hook() before your patch. But yeah it's better to do it > earlier as the freed object's user is who charged it to the memcg, and is no > longer using it - no reason to keep it accounted while in kasan's quarantine. > I couldn't agree more. Thanks.