From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BDFAC433EF for ; Tue, 21 Dec 2021 13:16:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F118E6B0073; Tue, 21 Dec 2021 08:16:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ECAAC6B0074; Tue, 21 Dec 2021 08:16:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D12B46B0075; Tue, 21 Dec 2021 08:16:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0059.hostedemail.com [216.40.44.59]) by kanga.kvack.org (Postfix) with ESMTP id C3ABF6B0073 for ; Tue, 21 Dec 2021 08:16:30 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 853FB181AC9C6 for ; Tue, 21 Dec 2021 13:16:30 +0000 (UTC) X-FDA: 78941850540.27.149C326 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) by imf30.hostedemail.com (Postfix) with ESMTP id 2C6CA80032 for ; Tue, 21 Dec 2021 13:16:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=GBBnAb3uzp4suSaLhtbSHK02SXI8tanA6M9OarZBIic=; b=HtWgQ2UPNiBB+1pCTUpNRwXNWg 4YT+vCRicbSTUKU+aQvt504rRzWV/8P1JQRX07xiTCDwvNGbvwnvMsOPMKGOGfgULiTKoSOMzzq+V XcLZ117cDWyRFT2SvNM1eGltV+MTk7nsQcKZ6WQxJqsPX//00ELuBEBhVI+XevOCoYp/j7PwBljBR ILJsQ2a1tTui4sMuXK6PruhmMd7I9DAz323LS3znH6LXqx5mEzhflaXOVZApXNk8d0ouS9yhqUJl8 V1OW4BP0bGhVgzqRjLIOQ3GBsQUX6dCZ/9QWTcAiX6N0FrSAcOE2/5wBTY8MZShzGBfv1tKXgL2R+ K38yFwVA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mzezl-002jtH-DR; Tue, 21 Dec 2021 13:15:57 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id AF34030044A; Tue, 21 Dec 2021 14:15:56 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9D91A2072814B; Tue, 21 Dec 2021 14:15:56 +0100 (CET) Date: Tue, 21 Dec 2021 14:15:56 +0100 From: Peter Zijlstra To: Yury Norov Cc: linux-kernel@vger.kernel.org, "James E.J. Bottomley" , "Martin K. Petersen" , =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , "Paul E. McKenney" , "Rafael J. Wysocki" , Alexander Shishkin , Alexey Klimov , Amitkumar Karwar , Andi Kleen , Andrew Lunn , Andrew Morton , Andy Gross , Andy Lutomirski , Andy Shevchenko , Anup Patel , Ard Biesheuvel , Arnaldo Carvalho de Melo , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christoph Hellwig , Christoph Lameter , Daniel Vetter , Dave Hansen , David Airlie , David Laight , Dennis Zhou , Emil Renner Berthing , Geert Uytterhoeven , Geetha sowjanya , Greg Kroah-Hartman , Guo Ren , Hans de Goede , Heiko Carstens , Ian Rogers , Ingo Molnar , Jakub Kicinski , Jason Wessel , Jens Axboe , Jiri Olsa , Joe Perches , Jonathan Cameron , Juri Lelli , Kees Cook , Krzysztof Kozlowski , Lee Jones , Marc Zyngier , Marcin Wojtas , Mark Gross , Mark Rutland , Matti Vaittinen , Mauro Carvalho Chehab , Mel Gorman , Michael Ellerman , Mike Marciniszyn , Nicholas Piggin , Palmer Dabbelt , Petr Mladek , Randy Dunlap , Rasmus Villemoes , Russell King , Saeed Mahameed , Sagi Grimberg , Sergey Senozhatsky , Solomon Peachy , Stephen Boyd , Stephen Rothwell , Steven Rostedt , Subbaraya Sundeep , Sudeep Holla , Sunil Goutham , Tariq Toukan , Tejun Heo , Thomas Bogendoerfer , Thomas Gleixner , Ulf Hansson , Vincent Guittot , Vineet Gupta , Viresh Kumar , Vivien Didelot , Vlastimil Babka , Will Deacon , bcm-kernel-feedback-list@broadcom.com, kvm@vger.kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-csky@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-snps-arc@lists.infradead.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 13/17] kernel/cpu: add num_possible_cpus counter Message-ID: References: <20211218212014.1315894-1-yury.norov@gmail.com> <20211218212014.1315894-14-yury.norov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211218212014.1315894-14-yury.norov@gmail.com> X-Rspamd-Queue-Id: 2C6CA80032 X-Stat-Signature: feagbqenwy7ezo5xfap9kne6c8fr7bnx Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=desiato.20200630 header.b=HtWgQ2UP; spf=none (imf30.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.92.199) smtp.mailfrom=peterz@infradead.org; dmarc=none X-Rspamd-Server: rspam10 X-HE-Tag: 1640092590-267865 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 Sat, Dec 18, 2021 at 01:20:09PM -0800, Yury Norov wrote: > Similarly to the online cpus, the cpu_possible_mask is actively used > in the kernel. This patch adds a counter for possible cpus, so that > users that call num_possible_cpus() would know the result immediately, > instead of calling the bitmap_weight for the mask underlying. So what user actually cares about performance here enough to warrant this? > +EXPORT_SYMBOL(set_cpu_possible); NAK