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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 5E630C07E85 for ; Tue, 11 Dec 2018 18:09:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3040A20851 for ; Tue, 11 Dec 2018 18:09:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3040A20851 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726850AbeLKSJU (ORCPT ); Tue, 11 Dec 2018 13:09:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34032 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbeLKSJT (ORCPT ); Tue, 11 Dec 2018 13:09:19 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3613889AC5; Tue, 11 Dec 2018 18:09:19 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EEE5F1057069; Tue, 11 Dec 2018 18:09:17 +0000 (UTC) From: Jeff Moyer To: Jens Axboe Cc: Matthew Wilcox , Alexander Viro , Benjamin LaHaise , Andrew Morton , Kees Cook , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dan Carpenter , kent.overstreet@gmail.com Subject: Re: [PATCH] aio: Convert ioctx_table to XArray References: <20181128183531.5139-1-willy@infradead.org> <20181211175156.GF6830@bombadil.infradead.org> <0f77a532-0d88-78bc-b9cc-06bb203a0405@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Tue, 11 Dec 2018 13:09:17 -0500 In-Reply-To: <0f77a532-0d88-78bc-b9cc-06bb203a0405@kernel.dk> (Jens Axboe's message of "Tue, 11 Dec 2018 11:05:12 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 11 Dec 2018 18:09:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: > On 12/11/18 11:02 AM, Jeff Moyer wrote: >> Matthew Wilcox writes: >> >>> On Tue, Dec 11, 2018 at 12:21:52PM -0500, Jeff Moyer wrote: >>>> I'm going to submit this version formally. If you're interested in >>>> converting the ioctx_table to xarray, you can do that separately from a >>>> security fix. I would include a performance analysis with that patch, >>>> though. The idea of using a radix tree for the ioctx table was >>>> discarded due to performance reasons--see commit db446a08c23d5 ("aio: >>>> convert the ioctx list to table lookup v3"). I suspect using the xarray >>>> will perform similarly. >>> >>> There's a big difference between Octavian's patch and mine. That patch >>> indexed into the radix tree by 'ctx_id' directly, which was pretty >>> much guaranteed to exhibit some close-to-worst-case behaviour from the >>> radix tree due to IDs being sparsely assigned. My patch uses the ring >>> ID which _we_ assigned, and so is nicely behaved, being usually a very >>> small integer. >> >> OK, good to know. I obviously didn't look too closely at the two. >> >>> What performance analysis would you find compelling? Octavian's original >>> fio script: >>> >>>> rw=randrw; size=256k ;directory=/mnt/fio; ioengine=libaio; iodepth=1 >>>> blocksize=1024; numjobs=512; thread; loops=100 >>>> >>>> on an EXT2 filesystem mounted on top of a ramdisk >>> >>> or something else? >> >> I think the most common use case is a small number of ioctx-s, so I'd >> like to see that use case not regress (that should be easy, right?). Bah, I meant a small number of threads doing submit/getevents. >> Kent, what were the tests you were using when doing this work? Jens, >> since you're doing performance work in this area now, are there any >> particular test cases you care about? > > I can give it a spin, ioctx lookup is in the fast path, and for "classic" > aio we do it twice for each IO... Thanks! -Jeff