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 C377DC433F5 for ; Sun, 30 Jan 2022 20:49:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A30CA6B0071; Sun, 30 Jan 2022 15:49:40 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9E0F56B0073; Sun, 30 Jan 2022 15:49:40 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 881716B0074; Sun, 30 Jan 2022 15:49:40 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0117.hostedemail.com [216.40.44.117]) by kanga.kvack.org (Postfix) with ESMTP id 760EC6B0071 for ; Sun, 30 Jan 2022 15:49:40 -0500 (EST) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 2C4508249980 for ; Sun, 30 Jan 2022 20:49:40 +0000 (UTC) X-FDA: 79088144520.31.B9EFD3E Received: from mail-pj1-f54.google.com (mail-pj1-f54.google.com [209.85.216.54]) by imf04.hostedemail.com (Postfix) with ESMTP id B7EBB40007 for ; Sun, 30 Jan 2022 20:49:39 +0000 (UTC) Received: by mail-pj1-f54.google.com with SMTP id s61-20020a17090a69c300b001b4d0427ea2so16233065pjj.4 for ; Sun, 30 Jan 2022 12:49:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:in-reply-to:message-id:references :mime-version; bh=aE3FiEfD4YX71c3f0yLgS/uNySrINu0tsaBgzhna2ek=; b=Zjc4YSbGgk5QwhyB+a51LM72RbO00quYJOUYe1md1PNeyr/pecUXyZy7c65ujwauiA CUXD+drBbDEDTaQ4MV92WmTsZfC1dJ8T8yrwIOweCjuFhprfvSu8cEBcojLm4+52bSK3 hjteoxIHrZN7kcEWFRqyz9jfr3ZIvCrsWiL8+zSAtgeBonKZzynzshN8x3jZCgWYXTsy f3jg0rnNBNZh7xLjmAYXc8WSRADrZEQTFdN0a9S1En9/RjEz98r1OKDSxZdZ6AS+ctMq EcyxQCOAQSj95T6quv5E/UQAfAfzA+PKBTErMyBRTY9t23qn6560MJ0PuKndvNAQsRY3 qj/Q== 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:in-reply-to:message-id :references:mime-version; bh=aE3FiEfD4YX71c3f0yLgS/uNySrINu0tsaBgzhna2ek=; b=7WbB9sJDWk2PZfHHpqfJb9fGIQwoz55wHGpe6pLCrW/C/UW6fMBJGG10Eke6UEA3sW xY2fJtSF4mDZhMuHof0KQYq3FJ29OP4cGE7qI05yV3s6NipZDAmFUqwQ7F3vTcbn3jOc 4tBJYW379Dl8yfAoW6sZbsAnl1ZX2vN47FxcxuIVu45COed8KPKmuynTLxUR/jLNP4s/ ULLBsD1PzQjBOfoQ4kV/R5G2ohbfCHvPZLOoqMhfFoY+r+fLlp1WFHOFMUyWLFwevUas mFj6cXzjmOiBaxaDj3U+/cH3TrubZfEvWTWSzcPoJMxhMIPX2qbWVDsAJMVHG3DDalmQ Y2cw== X-Gm-Message-State: AOAM532usZ01rrnkqVwm/cP/6RPKpMfemO0yQWP45HtHZ/bPTO783inT 5camPVWGVqGkboo3d7lX6ZtVNA== X-Google-Smtp-Source: ABdhPJzknUBOF48IkBEUpy+P7QTvqoIlz5pQ0VVuk6JLHYZn5+JJKai/TswjaJ3CjRFcvKy4MFgcBw== X-Received: by 2002:a17:90a:8592:: with SMTP id m18mr21353483pjn.142.1643575778465; Sun, 30 Jan 2022 12:49:38 -0800 (PST) Received: from [2620:15c:29:204:2b97:ce13:593d:973d] ([2620:15c:29:204:2b97:ce13:593d:973d]) by smtp.gmail.com with ESMTPSA id f64sm12998472pfa.165.2022.01.30.12.49.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Jan 2022 12:49:38 -0800 (PST) Date: Sun, 30 Jan 2022 12:49:37 -0800 (PST) From: David Rientjes 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 In-Reply-To: <20220129205315.478628-2-longman@redhat.com> 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 X-Rspamd-Queue-Id: B7EBB40007 X-Rspam-User: nil Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Zjc4YSbG; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf04.hostedemail.com: domain of rientjes@google.com designates 209.85.216.54 as permitted sender) smtp.mailfrom=rientjes@google.com X-Stat-Signature: hkkrdubrpe8gf7ai59m75rkozd66rdmo X-Rspamd-Server: rspam08 X-HE-Tag: 1643575779-289286 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, 29 Jan 2022, 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 > --- > lib/vsprintf.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 3b8129dd374c..a65df546fb06 100644 > --- a/lib/vsprintf.c > +++ 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; Nit: any reason this shouldn't be unlikely()? If the conditional for i < size is likely(), this seems assumed already? > + > 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); > > -- > 2.27.0 > > >