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 20646C433EF for ; Sun, 17 Apr 2022 01:43:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 42E2B6B0072; Sat, 16 Apr 2022 21:43:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3B5236B0073; Sat, 16 Apr 2022 21:43:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2302E6B0074; Sat, 16 Apr 2022 21:43:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0134.hostedemail.com [216.40.44.134]) by kanga.kvack.org (Postfix) with ESMTP id 10B3D6B0072 for ; Sat, 16 Apr 2022 21:43:32 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id B2438A5D4E for ; Sun, 17 Apr 2022 01:43:31 +0000 (UTC) X-FDA: 79364673822.29.4632A93 Received: from mail-pj1-f47.google.com (mail-pj1-f47.google.com [209.85.216.47]) by imf18.hostedemail.com (Postfix) with ESMTP id 46B6B1C0002 for ; Sun, 17 Apr 2022 01:43:31 +0000 (UTC) Received: by mail-pj1-f47.google.com with SMTP id z6-20020a17090a398600b001cb9fca3210so11323774pjb.1 for ; Sat, 16 Apr 2022 18:43:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=YGLhajMrQZ0HNv4gi0NLxOpmUqsJjdy2hqp78V6xiwY=; b=g//V0jscMI2Iyi2QAQ+PFI2DZw+WBUeb1QJwsZJbLNu7fgV9Th/w+uwsLB5E7zAhI9 yygUNRHTbNBt9yDOep7SnjvKtg6Cxe0AqZfDkAQyNJeICjR9ZhWWkbLaLap1N3oSdA/+ O1bkxjJuTmaRSzucphnqxJfqfZPkKUmiLat/pdTy+TTaI5ej/z60OJI8OcDXAFiElWhl jDaXE0XACzc4ZlmZ0S1/90AjwKDyiGbelicBz08DAlgQGBbDIblDSU5uQ4w3i4/k9OCq E5UrugBJ8OSw5OOfy2KSzL6fZaWqLXeMY6JwXoVK8HdYmbUsovmdAzpTn9CYOWrfzEFj NLqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=YGLhajMrQZ0HNv4gi0NLxOpmUqsJjdy2hqp78V6xiwY=; b=hVQX+NcGgjzd/GCbvjwUXPK6S+EbXwP3Sg60I8BMIXcxWaszic0siN58Oj9MlKV/V/ VFZV9TNA8STvuKv1YlVo7xnIkuFJHx50Q99IX0cqlCB3j7YPxZZHqzqQjoBR0ScTVKVd jtuJviTnaU8DzoiAAAinBUcoiIo07Q3uVlIqS9c5gnBOyJEOy3QbRYOZLcF6Mra2g1Ti 5L5l+NubKk/fXmEbc+OTzfI8cK2f3huNleOl2TEVUoO5Ab+Ouo/hhkIxur0xM9OwyG26 Sl8BlsgZeZNrBubZtXFsiWyH2slOiUVgjN1fHhb5sWeJ5UvIVAekVg17Kff4BJH+NemD cfzA== X-Gm-Message-State: AOAM533hqZ6bch9VMrObUuclkQDsyO6Toh78aD0N39qLydEa3mHOzipo Ngg8irWd/IbUdBkLXEUbcfA= X-Google-Smtp-Source: ABdhPJyOwejMu2zDtBa0GmDs8EK961A5N3tydC83+EkD4XBsRu3AhBC5J/Bj8v/SxRY99nVJptNTtg== X-Received: by 2002:a17:902:ea0a:b0:158:acff:ff89 with SMTP id s10-20020a170902ea0a00b00158acffff89mr5593131plg.88.1650159810180; Sat, 16 Apr 2022 18:43:30 -0700 (PDT) Received: from hyeyoo ([114.29.24.243]) by smtp.gmail.com with ESMTPSA id u25-20020aa78399000000b00505f75651e7sm7049105pfm.158.2022.04.16.18.43.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 16 Apr 2022 18:43:28 -0700 (PDT) Date: Sun, 17 Apr 2022 10:43:20 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Wonhyuk Yang Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Ohhoon Kwon , JaeSang Yoo , Jiyoup Kim , Donghyeok Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/slub: Remove repeated action in calculate_order() Message-ID: References: <20220416074059.526970-1-vvghjk1234@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220416074059.526970-1-vvghjk1234@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 46B6B1C0002 X-Stat-Signature: rnya8qqqko4qqr5bbty84f5querfd1dk Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="g//V0jsc"; spf=pass (imf18.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.216.47 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-HE-Tag: 1650159811-580379 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, Apr 16, 2022 at 04:40:59PM +0900, Wonhyuk Yang wrote: > To calculate order, calc_slab_order() is called repeatly changing the > fract_leftover. Thus, the branch which is not dependent on > fract_leftover is executed repeatly. So make it run only once. > > Plus, when min_object reached to 0, we set fract_leftover to 1. In Maybe you mean when min_object reached 1. > this case, we can calculate order by max(slub_min_order, > get_order(size)) instead of calling calc_slab_order(). > > No functional impact expected. > Signed-off-by: Wonhyuk Yang > --- > V1 -> V2: Fix typo miss in a commit message > > mm/slub.c | 18 +++++++----------- > 1 file changed, 7 insertions(+), 11 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index ed5c2c03a47a..e7a394d7b75a 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3795,9 +3795,6 @@ static inline unsigned int calc_slab_order(unsigned int size, > unsigned int min_order = slub_min_order; > unsigned int order; > > - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) > - return get_order(size * MAX_OBJS_PER_PAGE) - 1; > - > for (order = max(min_order, (unsigned int)get_order(min_objects * size)); > order <= max_order; order++) { > > @@ -3820,6 +3817,11 @@ static inline int calculate_order(unsigned int size) > unsigned int max_objects; > unsigned int nr_cpus; > > + if (unlikely(order_objects(slub_min_order, size) > MAX_OBJS_PER_PAGE)) { > + order = get_order(size * MAX_OBJS_PER_PAGE) - 1; > + goto out; > + } > + > /* > * Attempt to find best configuration for a slab. This > * works by first attempting to generate a layout with > @@ -3865,14 +3867,8 @@ static inline int calculate_order(unsigned int size) > * We were unable to place multiple objects in a slab. Now > * lets see if we can place a single object there. > */ > - order = calc_slab_order(size, 1, slub_max_order, 1); > - if (order <= slub_max_order) > - return order; > - > - /* > - * Doh this slab cannot be placed using slub_max_order. > - */ > - order = calc_slab_order(size, 1, MAX_ORDER, 1); > + order = max_t(unsigned int, slub_min_order, (unsigned int)get_order(size)); > +out: You don't need to cast value of get_order(size). max_t() does cast both operands. > if (order < MAX_ORDER) > return order; > return -ENOSYS; For the correctness of the patch, I don't see any problem about the code. But to be honest I'm a bit skeptical about saving some cycles in calculating slab order. It's done only when creating caches (usually in boot process). > -- > 2.30.2 > > -- Thanks, Hyeonggon