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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 2686CC3A589 for ; Thu, 15 Aug 2019 19:31:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EC1DB20656 for ; Thu, 15 Aug 2019 19:31:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="W/vU/7xc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731509AbfHOTbG (ORCPT ); Thu, 15 Aug 2019 15:31:06 -0400 Received: from mail-io1-f65.google.com ([209.85.166.65]:46580 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731334AbfHOTbG (ORCPT ); Thu, 15 Aug 2019 15:31:06 -0400 Received: by mail-io1-f65.google.com with SMTP id x4so1453935iog.13 for ; Thu, 15 Aug 2019 12:31:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=0zU1UzGhGpSs42osUb1VwxYmT+F95oS3ySvyshFJEKk=; b=W/vU/7xc7p47Vimmqfb1G2QAFDNTCqMFaGRsHe74Wkbx3UmQHnCznpOGppBbaqTWcc +VolBhjCxYDeXdliOmI2HmmxY4nH8B8J+UBWDvk+IL36DHmxcQmAU1ln3BX7cctIfCBF yjwLo/ZtJOegnWApB777y2VXG2wTFCipZVImeKD1AtIYfliO9cqFDmP8BCzcekMgAXuu Zw9Kmzt3+xaa4mJg6S0NR9wwpYJK4FjvLmgDrPv1UWddx0BEpCy/bwkd95d1TrvQsNKP JCQRpzjCTHUGnQCc7F0fhTww1+q9U2m4YSB9y9BKNZqZSTOrrvp07VVWalqxEYnHimfO wHKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=0zU1UzGhGpSs42osUb1VwxYmT+F95oS3ySvyshFJEKk=; b=koA6PRd0XdJnPJSPZ3GFIl1rdyV6Mkrj7Re6oIRhJgtactkYHdBx+4HBsv2UR5T1hu d0ZkIS1uPWUTtC6HDifpfN1tfrT4TVWUlkQOKs1tDLLXE5r/Cx4OXS2DmHNkcRCTs9dC t4OQZ/Gjcr6bJWuxozKcjEiBn+Hh7R1uPv4yAb1e/RCA4EQi/BKZaxviQVrYWKYz97qA gN2QP9BHES6aZQl0rA83mMlfQqORPyDfbJ+XQ9aaQoxzh0OE33bsa96lFsGTBGNQIUAB 6BPQdrb7Webu8H0q7jCEtnNeDrW9BGdpk0wiG2caj6naL1gbthSgxaccj8AWSHFUGcyl EhZQ== X-Gm-Message-State: APjAAAWPrLVlAMA7YDvjBUMdSmdI+wJOxP4imECnI1/j3Hx9tfWkg1QY A78OV7OqKN5O5Lwq3ZrF8BNuzg== X-Google-Smtp-Source: APXvYqzqTPRFTBKjlHaL1Hke9CdTLw+pYgxq+9XjlO17fN4eFFBk9o/pg1C4j6n/IYoXtb76mhp+Yg== X-Received: by 2002:a5d:9448:: with SMTP id x8mr7675761ior.102.1565897465344; Thu, 15 Aug 2019 12:31:05 -0700 (PDT) Received: from [192.168.1.50] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id h8sm2468682ioq.61.2019.08.15.12.31.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 15 Aug 2019 12:31:03 -0700 (PDT) Subject: Re: [PATCH v2 block 1/2] writeback, cgroup: Adjust WB_FRN_TIME_CUT_DIV to accelerate foreign inode switching To: Tejun Heo , Jan Kara Cc: linux-block@vger.kernel.org, kernel-team@fb.com, linux-kernel@vger.kernel.org References: <20190802190738.GB136335@devbig004.ftw2.facebook.com> <20190815192528.GA2240241@devbig004.ftw2.facebook.com> From: Jens Axboe Message-ID: Date: Thu, 15 Aug 2019 13:31:02 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190815192528.GA2240241@devbig004.ftw2.facebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 8/15/19 1:25 PM, Tejun Heo wrote: > WB_FRN_TIME_CUT_DIV is used to tell the foreign inode detection logic > to ignore short writeback rounds to prevent getting confused by a > burst of short writebacks. The parameter is currently 2 meaning that > anything smaller than half of the running average writback duration > will be ignored. > > This is unnecessarily aggressive. The detection logic uses 16 history > slots and is already reasonably protected against some short bursts > confusing it and the current parameter can lead to tens of seconds of > missed detection depending on the writeback pattern. > > Let's change the parameter to 8, so that it only ignores writeback > with are smaller than 12.5% of the current running average. > > v2: Add comment explaining what's going on with the foreign detection > parameters. Applied 1-2 for 5.4, thanks. -- Jens Axboe