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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 77225C388F9 for ; Sat, 21 Nov 2020 18:23:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3688422206 for ; Sat, 21 Nov 2020 18:23:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="dH00Lj87" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727048AbgKUSXe (ORCPT ); Sat, 21 Nov 2020 13:23:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35838 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727032AbgKUSXe (ORCPT ); Sat, 21 Nov 2020 13:23:34 -0500 Received: from mail-lf1-x143.google.com (mail-lf1-x143.google.com [IPv6:2a00:1450:4864:20::143]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3301C061A4A for ; Sat, 21 Nov 2020 10:23:33 -0800 (PST) Received: by mail-lf1-x143.google.com with SMTP id u18so18103957lfd.9 for ; Sat, 21 Nov 2020 10:23:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=m7cZfFDWETupzrz1W/PA0N75+saduUeI+gk15nXI7Q0=; b=dH00Lj87XUWDjVhZTS31u5fK+b2ZiXmaVewWBK/V48aWDdpvmlY8lYEZ3TsPZy+JuP Piggiet9UE2qE2SNHmspoYRK7bxHTomINqVwsLJcANApC/MOgACoEjU5ZxHckGmnDp1N lQ0V7X3C4QU5N8npwm/3beAXsfs54Clu8S4xY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=m7cZfFDWETupzrz1W/PA0N75+saduUeI+gk15nXI7Q0=; b=S2WSFVyY5CfTi0kEJJMm8G9Yiuncf6+dO0yYSjQixrVk3m4U2iVQJDV9af5IQzRlat +q2NC2Pl8ejXy/GAJC4/ThfwtgxMeRb4WFCq8SUlB/bTsiC0lRbiVVZsbwWYHDhZJl2Q dCK1hIwjSFdnCVw/gLwgR9Gxky5nVno4mdS8AHKUU/uJ/Tl0t6lzDUkZsd1p7S4/2tcR O1GsCTY5a8NU8j+qmALCGjkYvdUhboCzerXcM1RttZ9Cgt1fX0aAFP3b+YgIL8LUR96P F8gvm9pfIL/zyUfn8mUm6IV7Wdcag0U59qSFobPbz2uReHIRecsrCPi+1jKdbjoHozSo r69A== X-Gm-Message-State: AOAM53102eKVSyM9PwG8MVV2qKWh2CNqeL+uq1JRp3YTSwN/ePE8Krmk wUW4U1DXPVFaCWDLbPD0oMKP73sp2mcw8A== X-Google-Smtp-Source: ABdhPJwqOAtwsouRn9aafr82f0vKlAj+Yh8O8qmrWv+l47+gU3aaxpIbRaLzcmDw8GdoZJtPJhRWjQ== X-Received: by 2002:a19:5d55:: with SMTP id p21mr815424lfj.115.1605983011678; Sat, 21 Nov 2020 10:23:31 -0800 (PST) Received: from mail-lf1-f52.google.com (mail-lf1-f52.google.com. [209.85.167.52]) by smtp.gmail.com with ESMTPSA id r7sm782506lfc.206.2020.11.21.10.23.29 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 21 Nov 2020 10:23:30 -0800 (PST) Received: by mail-lf1-f52.google.com with SMTP id z21so18082812lfe.12 for ; Sat, 21 Nov 2020 10:23:29 -0800 (PST) X-Received: by 2002:a19:ae06:: with SMTP id f6mr11146486lfc.133.1605983009454; Sat, 21 Nov 2020 10:23:29 -0800 (PST) MIME-Version: 1.0 References: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> In-Reply-To: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> From: Linus Torvalds Date: Sat, 21 Nov 2020 10:23:13 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 00/29] RFC: iov_iter: Switch to using an ops table To: David Howells Cc: Pavel Begunkov , Matthew Wilcox , Jens Axboe , Alexander Viro , linux-fsdevel , linux-block , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sat, Nov 21, 2020 at 6:13 AM David Howells wrote: > > Can someone recommend a good way to benchmark this properly? The problem > is that the difference this makes relative to the amount of time taken to > actually do I/O is tiny. Maybe try /dev/zero -> /dev/null to try a load where the IO itself is cheap. Or vmsplice to /dev/null? Linus