From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Subject: Re: [PATCH v2 1/3] lib/vsprintf: Avoid redundant work with 0 size Date: Mon, 31 Jan 2022 11:53:40 +0900 Message-ID: References: <20220129205315.478628-1-longman@redhat.com> <20220129205315.478628-2-longman@redhat.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6nez3pOZHeNZeiNmWCxSv7m+o4l1wZUkGv8l3sBghcI=; b=bl5s49Mf5Jo0PPhp/YsG2pTfX/cSkte5Lb2YhdUnfcNtzIDFxkyo9yob+m2iPtZt5l xv1Vy09vmGfTJgQMgshwZY6wjI8DTo9tDQAicdQ1O3Aqys0vTHUn6jxnEoqVLuU2iR4W zrtwNdfbEMlcxfBvB1g967RSxbAm1PeIBDoKQ= Content-Disposition: inline In-Reply-To: <20220129205315.478628-2-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Waiman Long Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Ira Weiny , Rafael Aquini On (22/01/29 15:53), Waiman Long wrote: > For *scnprintf(), vsnprintf() is always called even if the input size is > 0. That is a waste of time, so just return 0 in this case. > > Signed-off-by: Waiman Long Reviewed-by: Sergey Senozhatsky > +++ b/lib/vsprintf.c > @@ -2895,13 +2895,15 @@ int vscnprintf(char *buf, size_t size, const char *fmt, va_list args) > { > int i; > > + if (!size) > + return 0; > + > i = vsnprintf(buf, size, fmt, args); > > if (likely(i < size)) > return i; > - if (size != 0) > - return size - 1; > - return 0; > + > + return size - 1; > } > EXPORT_SYMBOL(vscnprintf); 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 7EA14C433F5 for ; Mon, 31 Jan 2022 02:53:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9D0686B00A2; Sun, 30 Jan 2022 21:53:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 97FDF6B00A3; Sun, 30 Jan 2022 21:53:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 820096B00A4; Sun, 30 Jan 2022 21:53:48 -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 71B026B00A2 for ; Sun, 30 Jan 2022 21:53:48 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id ECD1397911 for ; Mon, 31 Jan 2022 02:53:47 +0000 (UTC) X-FDA: 79089062094.22.989413C Received: from mail-pf1-f175.google.com (mail-pf1-f175.google.com [209.85.210.175]) by imf30.hostedemail.com (Postfix) with ESMTP id 9160380004 for ; Mon, 31 Jan 2022 02:53:47 +0000 (UTC) Received: by mail-pf1-f175.google.com with SMTP id i17so11686912pfq.13 for ; Sun, 30 Jan 2022 18:53:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6nez3pOZHeNZeiNmWCxSv7m+o4l1wZUkGv8l3sBghcI=; b=bl5s49Mf5Jo0PPhp/YsG2pTfX/cSkte5Lb2YhdUnfcNtzIDFxkyo9yob+m2iPtZt5l xv1Vy09vmGfTJgQMgshwZY6wjI8DTo9tDQAicdQ1O3Aqys0vTHUn6jxnEoqVLuU2iR4W zrtwNdfbEMlcxfBvB1g967RSxbAm1PeIBDoKQ= 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=6nez3pOZHeNZeiNmWCxSv7m+o4l1wZUkGv8l3sBghcI=; b=EmRmtne9jD2ueTAJLOQqP4OPvzvgpBs2VygrKqmQoXo3L3apMqw/0RQ5RoLqKPPLwZ TuywEfMzLDXGwR5rBpCp72tMH6PkxnAaAxafnFrCOxBD63gX4gTWiOtCRbMCOesKAMSO hkjHhopCiIQFPxaiMDXl484C6f8LakSBfKYk8HMSvbwlDtmvOiO+/7zF/FuK4qJgfSaj YYql+gY4AOPo4muS/XKEIrPga9FTOop9Brp4upTacMOmjnhEv+FUIYmqni0TnkqduSrx 63BCxSNRIjwcig6DSiU1895uVC57qnxgmcQV6WHf9lH/cIwThUCB0hM1xwK2XUlv6j40 dNlQ== X-Gm-Message-State: AOAM532fFwHuktGtCqJsWPlnSI+6hWz4tNgejGn/oRU7r4YpmqFIAXQJ UqhzTShI1fF18P0M1tcUTn5eo7ntReXOFw== X-Google-Smtp-Source: ABdhPJzO+7lFn8ygZzzqkaFmFJWnpaPl2WneC2yR92lFloNUW2Ont7/aPnzolC2YcwGu0sJ4yGqn2g== X-Received: by 2002:a63:2a92:: with SMTP id q140mr15200339pgq.379.1643597626524; Sun, 30 Jan 2022 18:53:46 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:c6d0:3c7:e220:605c]) by smtp.gmail.com with ESMTPSA id y128sm17628695pfb.75.2022.01.30.18.53.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Jan 2022 18:53:45 -0800 (PST) Date: Mon, 31 Jan 2022 11:53:40 +0900 From: Sergey Senozhatsky To: Waiman Long Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Ira Weiny , Rafael Aquini Subject: Re: [PATCH v2 1/3] lib/vsprintf: Avoid redundant work with 0 size Message-ID: References: <20220129205315.478628-1-longman@redhat.com> <20220129205315.478628-2-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220129205315.478628-2-longman@redhat.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 9160380004 X-Stat-Signature: dcdy8rdazc7na8rmu3a8sihg68pc5zui Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=bl5s49Mf; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf30.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.175 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org X-Rspam-User: nil X-HE-Tag: 1643597627-296347 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 (22/01/29 15:53), Waiman Long wrote: > For *scnprintf(), vsnprintf() is always called even if the input size is > 0. That is a waste of time, so just return 0 in this case. > > Signed-off-by: Waiman Long Reviewed-by: Sergey Senozhatsky > +++ b/lib/vsprintf.c > @@ -2895,13 +2895,15 @@ int vscnprintf(char *buf, size_t size, const char *fmt, va_list args) > { > int i; > > + if (!size) > + return 0; > + > i = vsnprintf(buf, size, fmt, args); > > if (likely(i < size)) > return i; > - if (size != 0) > - return size - 1; > - return 0; > + > + return size - 1; > } > EXPORT_SYMBOL(vscnprintf);