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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39811C433EF for ; Sun, 30 Jan 2022 20:49:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347646AbiA3Utr (ORCPT ); Sun, 30 Jan 2022 15:49:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347586AbiA3Utj (ORCPT ); Sun, 30 Jan 2022 15:49:39 -0500 Received: from mail-pl1-x631.google.com (mail-pl1-x631.google.com [IPv6:2607:f8b0:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5701C061714 for ; Sun, 30 Jan 2022 12:49:39 -0800 (PST) Received: by mail-pl1-x631.google.com with SMTP id y17so10747872plg.7 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=TCbG4xZNTCh3wd4m2ORJkvNX+o4LWSuPkGwGf+nthINR24HPLtI0zkVbUnU0FLdYNd tWcoV2yi/XPX33P1Q4kngQTfauAPRPd16Ns9fZUYB+oIzTqfQkbAp6UGCLQysvNCAQNu f/RpklhxRovL/fJmfIDM9k/R8XG3LLYr3++s6WygcDi+hjj67STc3xVkUhqTYCXXy1yN uT6nHDl5NZHHIky/IPY3BY4hz2NsAfAb6KGWUr35/nnmNCWPdMKLBnsWwHYjaLiqi37b 9ZMZsCu1kQiNpOeZEqwxK1vTyBSeysHfe48A1DIOQn4wwcbKW3J2BwZybRG9nxw2EfxR EnJA== X-Gm-Message-State: AOAM531iuofAtyw77yPHKViBCqerjmzedfXVWyEBRseh28r4c+6KyFsU 6QN3HmPlJMnBvsMyCyKSuckM/A== 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > >