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=-3.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 183C7C433E7 for ; Mon, 19 Oct 2020 17:37:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A63F52224D for ; Mon, 19 Oct 2020 17:37:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ttaylorr-com.20150623.gappssmtp.com header.i=@ttaylorr-com.20150623.gappssmtp.com header.b="adpOKnUz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728182AbgJSRh2 (ORCPT ); Mon, 19 Oct 2020 13:37:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725887AbgJSRh2 (ORCPT ); Mon, 19 Oct 2020 13:37:28 -0400 Received: from mail-io1-xd43.google.com (mail-io1-xd43.google.com [IPv6:2607:f8b0:4864:20::d43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C365C0613CE for ; Mon, 19 Oct 2020 10:37:28 -0700 (PDT) Received: by mail-io1-xd43.google.com with SMTP id u19so645720ion.3 for ; Mon, 19 Oct 2020 10:37:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ttaylorr-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Pj0LQpwbJjf9NhbxiWfVBC4ffssGazuyB6A5fHKcqSo=; b=adpOKnUzfx8Gahr0ImNRSq5Xc7VXah0IrElECvJlel8uFyMvb3dKBdJskiVdLKgJDc XlmkQPoQZVTpxGg8LSOnAYbN4dTMcEgRJH/Gl+Ym/zd6LMc/14EU5Y91wG7xhmhWHD/r 6+eGb7vOZtcVPgSiX7VC5KCAyBNK4Ah5wC2dr90l3OZHEG35IfgBT6efU19zfK24Oc5L ZNuFt84sWT4RW3XcnUlKHQzUWZmw7x4h6ji6BXPz5+YaAHrOuneK9HhgLQL716jZb3LK 4xfezpRUeC31NL8lip80Du25vavpSkC/ma9Q2hxPGy4R8IHQtwrqS6uG/6N4xAhoQKaE +jeQ== 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; bh=Pj0LQpwbJjf9NhbxiWfVBC4ffssGazuyB6A5fHKcqSo=; b=XFARaNG4Fk2Rv7OzOSFzKTJdUXHOADjljR5YMTadQPqGt++lmvXw5DP+mVXHT6gkJ5 jSa3c8uekUYk2rjc2KgM9Dtq1Vo2vTObOF81fHtVe9qH4yJgdq4tqBB8I+kNITNv53Im elBcumTSVXw497qQ957maA0z5WWLjwXk9dq0/TK7Wqy784qCmuYn+zJ4+RgQ52UDUyPe 1f/Nm8oTY4AHjobkFMHGU/qoE1mp08k32Mw7sYhcWZJEEaIuWRO4VC87MaTh2esXd7d3 gwsmT4c72+he0sAjGpMeGlU9Ge95679PNsD69gPTQKjvFxuY7L8kY9iDDIVG/SguVsi1 mQ9A== X-Gm-Message-State: AOAM531OvTj/wzBUD5yHxXVAdli4lXpa3vYyPSpYvwT1ivDqK6x0aE/B u2DBg0wOAvyBNaLH1K9FDRgeYQ== X-Google-Smtp-Source: ABdhPJxh3e3L2vN8OdV6xCUHvMTX26BqBaw/w3oUxr6sFZzSDNFwMXZrQNma6zGZJOoYAKakX3Xqcg== X-Received: by 2002:a02:6242:: with SMTP id d63mr895689jac.19.1603129047393; Mon, 19 Oct 2020 10:37:27 -0700 (PDT) Received: from localhost ([2605:9480:22e:ff10:c096:f5e9:cd72:773e]) by smtp.gmail.com with ESMTPSA id 128sm386844iow.50.2020.10.19.10.37.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Oct 2020 10:37:26 -0700 (PDT) Date: Mon, 19 Oct 2020 13:37:24 -0400 From: Taylor Blau To: Junio C Hamano Cc: Taylor Blau , Nipunn Koorapati , Alex Vandiver via GitGitGadget , git@vger.kernel.org, Derrick Stolee , Utsav Shah , Alex Vandiver Subject: Re: [PATCH 1/4] fsmonitor: use fsmonitor data in `git diff` Message-ID: <20201019173724.GA42706@nand.local> References: <13fd992a375e30e8c7b0953a128e149951dee0ea.1602968677.git.gitgitgadget@gmail.com> <20201018041642.GB2262492@nand.local> <20201018234344.GC4204@nand.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Mon, Oct 19, 2020 at 10:23:26AM -0700, Junio C Hamano wrote: > Taylor Blau writes: > > >> > There is some overhead to invoke the hook and talk to watchman, but > >> > I'd expect that to be dwarfed by not having to issue O(# files) > >> > syscalls. > >> > >> "invoke the hook"---is that a pipe+fork+exec, or something else that > >> is far lighter-weight? > > > > The former; see 'fsmonitor.c:query_fsmonitor()'. > > It brings us back to the "overhead of how many lstat(2) takes us > closer to the overhead of a single pipe+fork+exec plus reading from > the pipe", doesn't it? Somewhat unfortunately, yes. Hopefully any user that cares to use fsmonitor has enough files in their repository that a pipe+fork+exec is still faster than however many lstats they would have needed otherwise. Of course, finding out what that number is is still interesting... Thanks, Taylor