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Fri, 22 Sep 2023 03:29:22 -0400 X-MC-Unique: ICVV_mQKOaG-pfcCcUitWA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 98D2F3C0F376; Fri, 22 Sep 2023 07:29:21 +0000 (UTC) Received: from localhost (unknown [10.72.112.35]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E171049BB9A; Fri, 22 Sep 2023 07:29:19 +0000 (UTC) Date: Fri, 22 Sep 2023 15:29:14 +0800 From: Baoquan He To: Vlastimil Babka Cc: David Rientjes , Christoph Lameter , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Jay Patel , Roman Gushchin , Pekka Enberg , Joonsoo Kim , linux-mm@kvack.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] mm/slub: refactor calculate_order() and calc_slab_order() Message-ID: References: <20230908145302.30320-6-vbabka@suse.cz> <20230908145302.30320-10-vbabka@suse.cz> <4662588e-fc8b-1854-57f8-d15e08a3c368@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4662588e-fc8b-1854-57f8-d15e08a3c368@suse.cz> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 X-Rspamd-Queue-Id: 77F1440007 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: bthwjarh1bypkam51dcpm5gxk6j8wnwj X-HE-Tag: 1695367768-169704 X-HE-Meta: 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 +NlyiQaN eeQCUMjkv15iEmanrFXWqb+ip2pQVuoShDKw7UP0mVEPlL7k7/cMvDd8B09r8fOLMJllU7stqKgU2Abc8JZdjSkzSiYXEMa2P3jB2dW5C2xj8cYwiixKROB2B414k/UkbARMGtoWsiM7V6V9BvdTI5svv94p3WLr5RtwIQsBIqMnMooDMjmoxs3sy6cSOkDidVQ5INubL8+k3kQzIoiaDD1Z2TlH8+HRuLSa7GhtzD9dbUstqo804b4QW5Mw7bHW1C3kqMWDCZVzCbu6KBEv3k4y4kT3osY20j1zAuslKAnBbq33vfTmYq+l7+3X+gHbg4/6/ 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 09/22/23 at 09:00am, Vlastimil Babka wrote: > On 9/16/23 03:28, Baoquan He wrote: > > On 09/08/23 at 04:53pm, Vlastimil Babka wrote: > >> @@ -4152,7 +4147,7 @@ static inline int calculate_order(unsigned int size) > >> * order on systems that appear larger than they are, and too > >> * low order on systems that appear smaller than they are. > >> */ > >> - nr_cpus = num_present_cpus(); > >> + unsigned int nr_cpus = num_present_cpus(); > >> if (nr_cpus <= 1) > >> nr_cpus = nr_cpu_ids; > >> min_objects = 4 * (fls(nr_cpus) + 1); > > > > A minor concern, should we change 'min_objects' to be a local static > > to avoid the "if (!min_objects) {" code block every time? It's deducing > > the value from nr_cpus, we may not need do the calculation each time. > > Maybe, although it's not a hot path. But we should make sure the > num_present_cpus() cannot change. Could it be e.g. low (1) very early when > we bootstrap the initial caches, but then update and at least most of the > caches then reflect the real number of cpus? With a static we would create > everything with 1. Yeah, I was silly, didn't think about it. We may check via system_state, but it's not worth to bother since it's not hot path as you said. Sorry for the noise.