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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,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 C5E86C433DF for ; Mon, 15 Jun 2020 19:10:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 93FC720768 for ; Mon, 15 Jun 2020 19:10:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592248221; bh=4ZZaot3vOXFQ4oupOtC24lNN5o+DJ/l8xbn0qgqEkJA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=K/AdcYdoiGElu94Hj5T42ZjZde/CeU5J+UGnpGKNqbpzSSja0zWUOYKDU1v3A9iqt MndZ19Z/hOUWpjVcSdq/olV/wc/+la3iBofgasc4ELdo8bBcwF1L+5cC5bUCGsr7hH 588Mu5OwC/vUeYhydIJimuhrgBQOZt43yUmwtpvQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731449AbgFOTKU (ORCPT ); Mon, 15 Jun 2020 15:10:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731371AbgFOTKT (ORCPT ); Mon, 15 Jun 2020 15:10:19 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3473C061A0E for ; Mon, 15 Jun 2020 12:10:18 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id i3so16010302ljg.3 for ; Mon, 15 Jun 2020 12:10:18 -0700 (PDT) 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=bLrasL53j1rcRe899kvLmCMS2kS/RWB75sihborwOiM=; b=DU/av6GzFEWftb06S7JjYSuQL7mwTQX2oFzubBhqTr2gBiqg95+qQX9FqcOTm9AjwQ Yq0zZ9x9/hOq8rqWpgeww9tEr2/8p15ZJQPl+E1hFXLI91NsEMARowGIpz1YT/Hxq+Ec tVOtVB/wETKIX+FyhrN8QKEePGQgISImY71OM= 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=bLrasL53j1rcRe899kvLmCMS2kS/RWB75sihborwOiM=; b=odEMpp8WnBSOL9lKU31bLFH22p356tEcwzezDZJPSwRnpHZFSBVmQNTNl6SQ3WqNDC Y21X3H8aDs3lwota8ElrH2oaxjO0OYRnMCKB8Oj3HY3MSn6ZdAoOre1CWHUzgLINBTxO tXrXmaBOdPeFdGgMynTyEvfUfm0GZJpCkW/ACySpJRwR24kxV8GVaVQQZlFXRn4N/WJ/ mzQPsRzG8sr/bDn5DOxBw4f1qTyGPbtbJiGgep7Ru0tomH22hoYfq6GPJnIQu9tjvWQC r5baa9ZIRAxzyd46HinxRUDUJA+dxvzvr5EjVB2UIqPszbYuv8Uk2WtAE3i8ViZjkDYA b3WQ== X-Gm-Message-State: AOAM532Vu/9ltrhQVFBlydvy6f1UFbtQZA6w/kWhHmfhbCcGh8U+lgjJ ggsThoAiZjDTyGl2fxDRSOehFIU3Lks= X-Google-Smtp-Source: ABdhPJzkYSIuAkPff+g2+RfU+hzz/xjjDjWe0zmuZis7QiW4x2LNBYVcgpS8GTJGPbN/0ff6igXcWQ== X-Received: by 2002:a2e:9b8f:: with SMTP id z15mr3860134lji.59.1592248216530; Mon, 15 Jun 2020 12:10:16 -0700 (PDT) Received: from mail-lj1-f174.google.com (mail-lj1-f174.google.com. [209.85.208.174]) by smtp.gmail.com with ESMTPSA id m14sm939012lfp.18.2020.06.15.12.10.15 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Jun 2020 12:10:15 -0700 (PDT) Received: by mail-lj1-f174.google.com with SMTP id x18so20510598lji.1 for ; Mon, 15 Jun 2020 12:10:15 -0700 (PDT) X-Received: by 2002:a2e:97c3:: with SMTP id m3mr14454425ljj.312.1592248214672; Mon, 15 Jun 2020 12:10:14 -0700 (PDT) MIME-Version: 1.0 References: <20200611040453.GK12456@shao2-debian> In-Reply-To: From: Linus Torvalds Date: Mon, 15 Jun 2020 12:09:58 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [gup] 17839856fd: stress-ng.vm-splice.ops_per_sec 2158.6% improvement To: Jann Horn Cc: kernel test robot , Christoph Hellwig , Oleg Nesterov , Kirill Shutemov , Jan Kara , Andrea Arcangeli , Matthew Wilcox , LKML , lkp@lists.01.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 15, 2020 at 12:33 AM Jann Horn wrote: > > So in summary I guess the test was just really slow up until now > because it was hitting a slowpath that you wouldn't hit during normal > usage? At least for vmsplice(), writing uninitialized pages doesn't > really make a whole lot of sense... Heh. My main worry with that commit was that we'd see the reverse effect: somebody implicitly depending on the continued sharing of pages in some odd splice situation, and where breaking the COW would result in a performance degradation. The fact that it went the other way instead is somewhat ironic. But good. I guess I'll just ping the stable people to say "yeah, put that in stable too". It's a fix, and apparently it _helps_ performance for the degenerate cases rather than hurting anything. Linus