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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 295B0C4363A for ; Thu, 29 Oct 2020 14:58:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3DE052076E for ; Thu, 29 Oct 2020 14:58:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="oc3AlERP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3DE052076E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 332EC6B005C; Thu, 29 Oct 2020 10:58:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2E3686B0071; Thu, 29 Oct 2020 10:58:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D28A6B0073; Thu, 29 Oct 2020 10:58:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0201.hostedemail.com [216.40.44.201]) by kanga.kvack.org (Postfix) with ESMTP id E25986B005C for ; Thu, 29 Oct 2020 10:58:04 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 7CD401EE6 for ; Thu, 29 Oct 2020 14:58:04 +0000 (UTC) X-FDA: 77425268088.13.cause59_3109bc52728e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 588F818140B60 for ; Thu, 29 Oct 2020 14:58:04 +0000 (UTC) X-HE-Tag: cause59_3109bc52728e X-Filterd-Recvd-Size: 3271 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Thu, 29 Oct 2020 14:58:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=HmfYod2GmMxvpGF38bdMbVaIZ4kE8IF6cgtgzxBjEeI=; b=oc3AlERPiwizRV8aRe0b9UHNmA PvjPAh2NqolvgY6Kcq6hzeFxA7O5nXNcgZ30hceYGMURaIZVLNATcrB4a/3zLAV3t2BUbfgu2WA/c uEangX8w1Pw0osXbDk/+T1VmhaR/SsiEq2lUVlpfnyJCEWLFSfuBaVJKKgZcavG2+zSDsbB99Humh Op7+QHDo3FkIIxhb82tlYcUJYcBEbRYTAV2Bs3ig++i9rdPWCb5T2a83DqWPISlSmV+6bGP8VbwGH vqRTNGnLVBIA4EQlLHrQ81mRjYdFLzOQySly9lmQ/KJnPGT+T47UYe6tFzDk9BOrP8eRnIcn3C5n1 lsMsVKIQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kY9NH-000587-Ie; Thu, 29 Oct 2020 14:58:00 +0000 Date: Thu, 29 Oct 2020 14:57:59 +0000 From: Matthew Wilcox To: Jens Axboe Cc: Andrew Morton , linux-mm@kvack.org, kent.overstreet@gmail.com Subject: Re: + fs-break-generic_file_buffered_read-up-into-multiple-functions.patch added to -mm tree Message-ID: <20201029145759.GA27442@casper.infradead.org> References: <20201025220817.XxXVE%akpm@linux-foundation.org> <20201027133551.GW20115@casper.infradead.org> <20201028152235.125172e46ae70ba4d7094469@linux-foundation.org> <543aa047-f334-cc40-8466-51bff70ac3b3@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <543aa047-f334-cc40-8466-51bff70ac3b3@kernel.dk> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 29, 2020 at 07:57:34AM -0600, Jens Axboe wrote: > On 10/28/20 4:26 PM, Jens Axboe wrote: > > I did see some wins when I tested this. I'll try and run some testing > > tomorrow and report back. If there's something specifically you want to > > see tested, let me know. > > I did some testing, unfortunately it's _very_ hard to produce somewhat > consistent and good numbers as it quickly becomes a game of kswapd. > Here's a basic case of 4 threads doing 32k random reads: > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 462 root 20 0 0 0 0 R 65.5 0.0 0:08.02 kswapd0 > 2287 axboe 20 0 1303448 2176 1072 R 46.6 0.0 0:05.35 fio > 2289 axboe 20 0 1303456 2196 1092 D 46.6 0.0 0:05.34 fio > 2290 axboe 20 0 1303460 2216 1112 D 46.6 0.0 0:05.37 fio > 2288 axboe 20 0 1303452 2224 1120 R 45.9 0.0 0:05.33 fio > > Sad face... Unfortunately once kswapd kicks in, performance also > plummets. This box only has 32G of ram, and you can fill that in less > than 10 seconds doing buffered reads like that. > > I ran 4k and 32k testing, and using 1 and 4 threads. But given the above > sadness, it quickly ends up looking the same for me. What if your workload actually fits in memory? That would seem to be the situation where Kent's patches would make a difference.