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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v2] mm: slab: optimize memcg_slab_free_hook() Content-Language: en-US To: Muchun Song , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, smuchun@gmail.com References: <20220429123044.37885-1-songmuchun@bytedance.com> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1655211544; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=SMr1/XLuAOMxSe9sGiC+UXBNDWGlTqQ/hao0UnZOiCI=; b=3xhUf7VPj1SCEktSaRkNbh8wJRIniyxmsHxNvbsrKEclcDT7ZztvcVVzoQf/MMqy6SHDtR sHnOFw/68RVCvE8SL9Zwz5c9p//TEH4xV7ydrra+80a5h609y/uLS6C8tOlSd0zrfTmQdI M2ygTwWt0WgLBVVPWyYinkmDrm4YOyA= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655211544; a=rsa-sha256; cv=none; b=GQlXpAID5//9yvKV6zACxIuG5XRuJ+qqaV/ykh7azK564lodd9cXZNNP8qQTzlvA7lVUsY elbRIKMP83hgj4xVmB/mLgiya7ALpmyweFgeUwhkx3fMn2K7tyYeavC7Slsfq2Nn8N8ceA LewkHU65DFQdfxqvtpkGFLLhHP7rQCQ= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=aqiIxHDc; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=hQCKkXMC; dmarc=none; spf=pass (imf19.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=aqiIxHDc; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=hQCKkXMC; dmarc=none; spf=pass (imf19.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.29 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Rspamd-Server: rspam12 X-Rspam-User: X-Stat-Signature: 83usshttgwfkfkwzmh4c5uqnun5cdi4o X-Rspamd-Queue-Id: 3C0D81A009C X-HE-Tag: 1655211544-522933 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 6/9/22 08:34, Muchun Song wrote: > On Fri, Apr 29, 2022 at 08:30:44PM +0800, 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") >> >> This optimization is mainly for bulk objects freeing. The following numbers >> is shown for 16-object freeing. >> >> before after >> kmem_cache_free_bulk: ~430 ns ~400 ns >> >> The overhead is reduced by about 7% for 16-object freeing. >> >> Signed-off-by: Muchun Song > > Hi Vlastimil, > > Wolud you mind picking it up? I did not see this patch on the > slab tree. Sorry, was waiting for rc1 to start the for-5.20 branches and was away for another week then. Now pushed to slab/for-5.20/optimizations > Thanks. >