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[194.45.78.10]) by smtp.gmail.com with ESMTPSA id n23-20020a170906841700b0099ce23c57e6sm1121679ejx.224.2023.08.18.05.32.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Aug 2023 05:32:47 -0700 (PDT) From: Jesper Dangaard Brouer X-Google-Original-From: Jesper Dangaard Brouer Message-ID: <0f77001b-8bd3-f72e-7837-cc0d3485aaf8@redhat.com> Date: Fri, 18 Aug 2023 14:32:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Cc: brouer@redhat.com, netdev@vger.kernel.org, vbabka@suse.cz, Eric Dumazet , "David S. Miller" , Jakub Kicinski , Paolo Abeni , linux-mm@kvack.org, Andrew Morton , Mel Gorman , Christoph Lameter , roman.gushchin@linux.dev, dsterba@suse.com Subject: Re: [PATCH net] net: use SLAB_NO_MERGE for kmem_cache skbuff_head_cache To: Matthew Wilcox , Jesper Dangaard Brouer , Vlastimil Babka References: <169211265663.1491038.8580163757548985946.stgit@firesoul> In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C3B7C40007 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: pr1do35h9rrc5ytf6m3x5ohaqiukuaky X-HE-Tag: 1692361971-278685 X-HE-Meta: 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 +ansrxUM 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 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 15/08/2023 17.53, Matthew Wilcox wrote: > On Tue, Aug 15, 2023 at 05:17:36PM +0200, Jesper Dangaard Brouer wrote: >> For the bulk API to perform efficiently the slub fragmentation need to >> be low. Especially for the SLUB allocator, the efficiency of bulk free >> API depend on objects belonging to the same slab (page). > > Hey Jesper, > > You probably haven't seen this patch series from Vlastimil: > > https://lore.kernel.org/linux-mm/20230810163627.6206-9-vbabka@suse.cz/ > > I wonder if you'd like to give it a try? It should provide some immunity > to this problem, and might even be faster than the current approach. > If it isn't, it'd be good to understand why, and if it could be improved. I took a quick look at: - https://lore.kernel.org/linux-mm/20230810163627.6206-11-vbabka@suse.cz/#Z31mm:slub.c To Vlastimil, sorry but I don't think this approach with spin_lock will be faster than SLUB's normal fast-path using this_cpu_cmpxchg. My experience is that SLUB this_cpu_cmpxchg trick is faster than spin_lock. On my testlab CPU E5-1650 v4 @ 3.60GHz: - spin_lock+unlock : 34 cycles(tsc) 9.485 ns - this_cpu_cmpxchg : 5 cycles(tsc) 1.585 ns - locked cmpxchg : 18 cycles(tsc) 5.006 ns SLUB does use a cmpxchg_double which I don't have a microbench for. > No objection to this patch going in for now, of course. >