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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27E74C433FE for ; Wed, 15 Dec 2021 17:45:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237789AbhLORpp (ORCPT ); Wed, 15 Dec 2021 12:45:45 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235513AbhLORpn (ORCPT ); Wed, 15 Dec 2021 12:45:43 -0500 Received: from mail-pj1-x102a.google.com (mail-pj1-x102a.google.com [IPv6:2607:f8b0:4864:20::102a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA136C061574; Wed, 15 Dec 2021 09:45:42 -0800 (PST) Received: by mail-pj1-x102a.google.com with SMTP id n15-20020a17090a160f00b001a75089daa3so21092777pja.1; Wed, 15 Dec 2021 09:45:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RLdWdHoT6O3wLXgWsRx2m2m62hSjV0BcJXlTjn5JUFY=; b=fVGVY8wqrxR8Y9FDXFtr4SE6iyR8BVVbZ5vgJ4y8dkqTnryOyAM1f7oIOnezuj4A6J xZUPr4yWMlNLYsHQ1fallxSJg8aU00+SwAnq0ijeJb6rpCasKd3VYye0HMu7Rz4Fmzli VTY7ooY+g0kHA+TAUoyyLgzX0mSn9ha1KmFllLdg51BzQBC+Mgmo9+XdPBjphX6Y4e34 aHA3UHFWRC7Btex9u1tZiEFoYFee/G/WGm4rYd3nNUPqV0MpixQGc6Vx0PruHv6wejmQ Ow0n2j4fyu9ba9vCZKTh9cTJvx1bERx0Yn7rh5DuRA2QxMZuAeUzJXU06wIQ9Mevfcss WI7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RLdWdHoT6O3wLXgWsRx2m2m62hSjV0BcJXlTjn5JUFY=; b=sXa4PcQUXBKlR2VROcfOlrvxsOIi4XVb+mljr5YNYnVds/2Me+M5DI44i8rGe9Rcnk UY8yugizTuUUUgzZfMVuh3URcNtM660AB1Gkd67ZcxQTgY24kDF9abv/x9fBJqAeEReX 7Zhgo7ET0YVC0GzDKs17CDVjYYvF160fhZSSG+SILcsHJRVm1vPoqWcO6rSfwCUaY+lV PlbbsWM06gUdehVGBC4896CjSbgZKstoR0VClDQoo6UyaLnWd9E9cshdwORHG/jN/RdJ xaV+ctip9qT+NOtVFAFVnv0azE6qDGv3C/xyePJvckwSI/ZKrDcygb4xLSWyNvJ6P6b4 7aPQ== X-Gm-Message-State: AOAM531bZh5ia5V0qOR9CYeeK4bH6cqyS2+9ClJCKIRMj41tZ4/JaYmR GzI4SXUAq703SpgzI+2TkhJHRYocxravu9zYHsQ= X-Google-Smtp-Source: ABdhPJxIcVzS1V95pBlMUcYP2k7Lrcyzl/rBNhnf3pbvrkTovj6aQvXpyQPCUffP2FcbLTl6T7AIgJQIhLFRrE2qAuQ= X-Received: by 2002:a17:90a:4a06:: with SMTP id e6mr968675pjh.228.1639590342342; Wed, 15 Dec 2021 09:45:42 -0800 (PST) MIME-Version: 1.0 References: <20211128035704.270739-1-yury.norov@gmail.com> <20211128035704.270739-3-yury.norov@gmail.com> <0ccb827de1164b2989d652bfb6f1bbab@AcuMS.aculab.com> In-Reply-To: <0ccb827de1164b2989d652bfb6f1bbab@AcuMS.aculab.com> From: Yury Norov Date: Wed, 15 Dec 2021 09:45:30 -0800 Message-ID: Subject: Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with bitmap_weight_eq() To: David Laight Cc: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , "linux-kernel@vger.kernel.org" , "James E.J. Bottomley" , "Martin K. Petersen" , "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 , Dennis Zhou , Dinh Nguyen , Geetha sowjanya , Geert Uytterhoeven , Greg Kroah-Hartman , Guo Ren , Hans de Goede , Heiko Carstens , Ian Rogers , Ingo Molnar , Jakub Kicinski , Jason Wessel , Jens Axboe , Jiri Olsa , Jonathan Cameron , Juri Lelli , Kalle Valo , 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 , Peter Zijlstra , Petr Mladek , Randy Dunlap , Rasmus Villemoes , Roy Pledge , 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" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 15, 2021 at 12:41 AM David Laight wrote: > > From: Yury Norov > > Sent: 14 December 2021 19:43 > ... > > > > I think that for long bitmaps the most time consuming operation is moving > > data to L1, and for short bitmaps the difference between approaches is > > barely measurable. > > > > But hweght_long on each iteration can't be more effective than the current > > version. So, I'll drop this patch for v2 and keep things unchanged. > > Actually do bitmap_full/empty() calls make any sense at all? > The result is stale since bitmaps are designed to do locked operations. > If you have a lock covering the bitmap then you should be using > something that uses non-locked accesses. > Rightly or wrongly that isn't the bitmap api. Are you talking about __{set,clear}_bit()? include/asm-generic/bitops/non-atomic.h