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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65395C3A5A6 for ; Thu, 19 Sep 2019 14:05:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 373EB20644 for ; Thu, 19 Sep 2019 14:05:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WnOLmi4X" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388181AbfISOFw (ORCPT ); Thu, 19 Sep 2019 10:05:52 -0400 Received: from mail-lf1-f68.google.com ([209.85.167.68]:37549 "EHLO mail-lf1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732252AbfISOFw (ORCPT ); Thu, 19 Sep 2019 10:05:52 -0400 Received: by mail-lf1-f68.google.com with SMTP id w67so2474905lff.4; Thu, 19 Sep 2019 07:05:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=h+oYWN2bIpXs7KBEHPN+VQbt2Knn5M+tAZIEiVvjPno=; b=WnOLmi4XV+fV599arvh4a2gZ61D35bWIW65sZl4YLcHgL7/9m9nDOASpZ6mqQ6XC2l GdZWsGc4tJambYUGw8KGL/NNyUy7l299bfuYXj/nOWdH++cO+ylhE/dFDT82KOEyfrUX 74HB9Fleun4Lz8khKtFolG4hQaZl5sV2UmAljYww8q47VrwS/bkYe4Va/kMf/9HZQlpI 5r4xitcBI4tfwi88E2mrI0pNqbUQkPNGJ1B7lMib2+rioqqqVhmabKllheM+RC5A+hU3 paH5b4MgaKleBDPJ+9I+uf0pON8CCULTEmCC3VBBRx5xANQlSBhDWcrLwjj60ED1wDLX tRjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=h+oYWN2bIpXs7KBEHPN+VQbt2Knn5M+tAZIEiVvjPno=; b=bo2qawVqye7fJMJYGiRHm7LaG6xnr3sXxaub8lIosO8q1iKMO5w/O6WRR1YjeF8e8l 7FPWr6FoHAaPRHnBrG4vwxVhOQYxyvMoyCZSS86wjbf2rJ4mIUPoZsk2HUyLK8pvMgJy 8aAGNH4h86RGGmSjace3+mZ32UZ8RBcn2JNEDRnyAA6qgeJ6d31GPkzLmDTaCEvBtmN1 oK5eHw3cxTWM3UJTc17yobxQ59uPGaUMIwOcFxcuAfXKuZU/RQrqkp+RznV8ixMkZBxf aXtO/ns6xrQdg8h1FgceH5hAIYT6cfbMDCy5568mn4oHVdYCA6ZmFs1iHn1vIsz/oYuw trjw== X-Gm-Message-State: APjAAAUwl3D+3tWgPmUCbCMzvBs1bah2ubJM1tZdgtpu4njZXqOrlUmq nGy9VS6vGZQ6TWucluK+wNI= X-Google-Smtp-Source: APXvYqxsPhcRFukc4IhdmQrXZloLSMPMyygyC8uuqAoW+bU7v9Y6FGk9oe/nfiOdkCTm7I9+kXY4xA== X-Received: by 2002:a19:ef05:: with SMTP id n5mr5030008lfh.192.1568901949733; Thu, 19 Sep 2019 07:05:49 -0700 (PDT) Received: from uranus.localdomain ([5.18.103.226]) by smtp.gmail.com with ESMTPSA id 77sm1689625ljf.85.2019.09.19.07.05.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Sep 2019 07:05:48 -0700 (PDT) Received: by uranus.localdomain (Postfix, from userid 1000) id ED6ED4614AD; Thu, 19 Sep 2019 17:05:47 +0300 (MSK) Date: Thu, 19 Sep 2019 17:05:47 +0300 From: Cyrill Gorcunov To: Dmitry Safonov Cc: linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Adrian Reber , Alexander Viro , Andrei Vagin , Andy Lutomirski , Ingo Molnar , Oleg Nesterov , Pavel Emelyanov , Thomas Gleixner , containers@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 4/9] select: Micro-optimise __estimate_accuracy() Message-ID: <20190919140547.GC2507@uranus.lan> References: <20190909102340.8592-1-dima@arista.com> <20190909102340.8592-5-dima@arista.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190909102340.8592-5-dima@arista.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 09, 2019 at 11:23:35AM +0100, Dmitry Safonov wrote: > Shift on s64 is faster than division, use it instead. > > As the result of the patch there is a hardly user-visible effect: > poll(), select(), etc syscalls will be a bit more precise on ~2.3% > than before because 1000 != 1024 :) > > Signed-off-by: Dmitry Safonov > --- > fs/select.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/fs/select.c b/fs/select.c > index 12cdefd3be2d..2477c202631e 100644 > --- a/fs/select.c > +++ b/fs/select.c > @@ -51,15 +51,14 @@ > > static long __estimate_accuracy(ktime_t slack) > { > - int divfactor = 1000; > - > if (slack < 0) > return 0; Btw, don't you better use <= here?