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 3C0DEC433DF for ; Thu, 4 Jun 2020 01:04:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1513720679 for ; Thu, 4 Jun 2020 01:04:26 +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="XOG7B0Uq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727878AbgFDBEV (ORCPT ); Wed, 3 Jun 2020 21:04:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41566 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726200AbgFDBEV (ORCPT ); Wed, 3 Jun 2020 21:04:21 -0400 Received: from mail-pj1-x1042.google.com (mail-pj1-x1042.google.com [IPv6:2607:f8b0:4864:20::1042]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E5478C08C5C0 for ; Wed, 3 Jun 2020 18:04:20 -0700 (PDT) Received: by mail-pj1-x1042.google.com with SMTP id jz3so339583pjb.0 for ; Wed, 03 Jun 2020 18:04:20 -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=o1u/ed182CTWV8ow6a1sNvTj56lmdVmqwb3Ugrhvu/U=; b=XOG7B0UqKMUBqsmoZP8owSJl9EczK6OxwF3SJPJbA3aYLAPGTl0/f/XWkbRf+ZHI6z gxdhlS0G7mu/aTcyOE+Q+VY6008fSTbJhPPxx1NyyjxNyC5UHJ+hh1GxbQzKOxMn/TVS xpg5G65SVDRkyk8hkTf895suzz6jRplA4wMYc/XQ5B0t3HlFxK+mrEvjpvD8GL525ZFC XgamVRkWG8Z0XGCSND93tk/EXitp9qsShjq09fjp1Mos5xuazTOmRUzmQeLMLA9UF42h kdBOildx92qTrLay+BF9nH2aXnxLvzST5gkY9Y0dyOJqzeE/2AGqSCwQaPANmfTx4kqq BkHQ== 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=o1u/ed182CTWV8ow6a1sNvTj56lmdVmqwb3Ugrhvu/U=; b=s9J4uwhfAzynyyrm5D+zUwf/ptlLfNC3yZPc/Tv0AWgGtqiahfwizydN904O86SHSU VYHojAvh8vr4QEpudZOLSc7Vy+0Uj6qsz3n38Jd4WZV381OQzIomsAMCHkwYp776H79j P8X+BVA1Rmj82Gyu4clO68mAq2FaosXyKQnqqOx0zi8ZOmpuDiRlGKA1rcHX3CyJ3yhH dIz/+x1N3f05FrGh3BeibBjsxPuGTdZqFFaxjn/RINW2YiHIIcv6X44VWOqQrYaR3QIV peKi6LDl6Cb5SfAVnvSQY6fTfWc5zO+pQn7jNydu72d5kPZK0KEfpCw1zlxUNAboMPGb 72aA== X-Gm-Message-State: AOAM531iRS5Ec9d6LP8FIgWhl+M+nVRTFDSKv0auOcb9iAvwRtud332k VseX8JjISKUs5lCb7WffQj2r/A== X-Google-Smtp-Source: ABdhPJwbOM4D7odfCkk3PeUCFQAJ68BerkNFfcVMjPgVIAg8AgGN6Jz9Tv9I+1N2b/H1jvH+Fj92XQ== X-Received: by 2002:a17:90a:642:: with SMTP id q2mr3082422pje.71.1591232660150; Wed, 03 Jun 2020 18:04:20 -0700 (PDT) Received: from [192.168.1.188] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id b6sm2889281pfp.24.2020.06.03.18.04.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Jun 2020 18:04:19 -0700 (PDT) Subject: Re: [PATCHSET v5 0/12] Add support for async buffered reads To: Andres Freund Cc: io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org References: <20200526195123.29053-1-axboe@kernel.dk> <20200604005916.niy2mejjcsx4sv6t@alap3.anarazel.de> From: Jens Axboe Message-ID: Date: Wed, 3 Jun 2020 19:04:17 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200604005916.niy2mejjcsx4sv6t@alap3.anarazel.de> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 6/3/20 6:59 PM, Andres Freund wrote: > Hi, > > I was trying to benchmark the benefits of this for the io_uring using > postgres I am working on. The initial results where quite promising > (reducing cpu usage significantly, to lower than non-uring sync io). But > unfortunately trying another workload triggered both panics and before > that seemingly returned wrong data. > > I first saw that problem with b360d424ce02, which was > linux-block/async-buffered.6 at the time. After hitting the issue, I > updated to the current linux-block/async-buffered.6, but the problem > persists. > > The workload that triggers the bug within a few seconds is postgres > doing a parallel sequential scan of a large table (and aggregating the > data, but that shouldn't matter). In the triggering case that boils down > to 9 processes sequentially reading a number of 1GB files (we chunk > tables internally into smaller files). Each process will read a 512kB > chunk of the file on its own, and then claim the next 512kB from a > shared memory location. Most of the IO will be READV requests, reading > 16 * 8kB into postgres' buffer pool (which may or may not be neighboring > 8kB pages). I'll try and reproduce this, any chance you have a test case that can be run so I don't have to write one from scratch? The more detailed instructions the better. > The io submissions in this case will all be done to the same io_uring, > targeting MAP_HUGETLB | MAP_SHARED | MAP_ANONYMOUS memory. The data is > on xfs. > > The benchmark starts with dropping caches, which helpfully is visible in > dmesg... That takes a few seconds, so the actual buffered io_uring load > starts soon after. > > [ 125.526092] tee (7775): drop_caches: 3 > [ 146.264327] kill_fasync: bad magic number in fasync_struct! > > After this, but before the oops, I see some userspace memory or > non-io-uring pipe reads being corrupted. > > > [ 146.264327] kill_fasync: bad magic number in fasync_struct! > [ 146.285175] kill_fasync: bad magic number in fasync_struct! > [ 146.290793] kill_fasync: bad magic number in fasync_struct! > [ 146.285175] kill_fasync: bad magic number in fasync_struct! > [ 146.290793] kill_fasync: bad magic number in fasync_struct! > [ 157.071979] BUG: kernel NULL pointer dereference, address: 0000000000000020 > [ 157.078945] #PF: supervisor read access in kernel mode > [ 157.084082] #PF: error_code(0x0000) - not-present page > [ 157.089225] PGD 0 P4D 0 > [ 157.091763] Oops: 0000 [#1] SMP NOPTI > [ 157.095429] CPU: 3 PID: 7756 Comm: postgres Not tainted 5.7.0-rc7-andres-00133-gc8707bf69395 #41 > [ 157.104208] Hardware name: Supermicro SYS-7049A-T/X11DAi-N, BIOS 3.2 11/13/2019 > [ 157.111518] RIP: 0010:xfs_log_commit_cil+0x356/0x7f0 > [ 157.116478] Code: 00 00 48 89 7e 08 49 89 76 30 48 89 11 48 89 4a 08 8b 4c 24 2c 48 89 85 c0 00 00 00 48 89 85 c8 00 00 00 49 8b 46 20 45 31 c9 <8b> 70 20 85 f6 0f 84 d9 02 00 00 45 31 c0 85 c9 7e 4f 41 8b 46 2c > [ 157.135226] RSP: 0018:ffffc90021fefb00 EFLAGS: 00010246 > [ 157.140452] RAX: 0000000000000000 RBX: ffff8897a9ea80b0 RCX: 0000000000000458 > [ 157.147582] RDX: ffff8897a9ea80c0 RSI: ffff88afc39a1200 RDI: ffff88afb1ae2c18 > [ 157.154715] RBP: ffff8897a9ea8000 R08: ffffc90021fefb30 R09: 0000000000000000 > [ 157.161848] R10: 0000000000000084 R11: 0000000000000012 R12: ffff8897721bd400 > [ 157.168983] R13: ffff88afb1ae2c00 R14: ffff88afb19860c0 R15: ffff8897a9ea80a0 > [ 157.176115] FS: 00007ffbbe9a1980(0000) GS:ffff8897e0cc0000(0000) knlGS:0000000000000000 > [ 157.184199] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 157.189946] CR2: 0000000000000020 CR3: 000000179c0ac005 CR4: 00000000007606e0 > [ 157.197081] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 157.204212] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 157.211343] PKRU: 55555554 > [ 157.214048] Call Trace: > [ 157.216498] __xfs_trans_commit+0xa1/0x340 > [ 157.220596] xfs_create+0x4cc/0x5e0 > [ 157.224087] xfs_generic_create+0x241/0x310 > [ 157.228274] path_openat+0xdb7/0x1020 > [ 157.231940] do_filp_open+0x91/0x100 > [ 157.235518] ? __sys_recvfrom+0xe4/0x170 > [ 157.239444] ? _cond_resched+0x19/0x30 > [ 157.243196] do_sys_openat2+0x215/0x2d0 > [ 157.247037] do_sys_open+0x44/0x80 > [ 157.250443] do_syscall_64+0x48/0x130 > [ 157.254108] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 157.259161] RIP: 0033:0x7ffbc0ded307 > [ 157.262738] Code: 25 00 00 41 00 3d 00 00 41 00 74 47 64 8b 04 25 18 00 00 00 85 c0 75 6b 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 95 00 00 00 48 8b 4c 24 28 64 48 33 0c 25 > [ 157.281485] RSP: 002b:00007fff520a4940 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 > [ 157.289052] RAX: ffffffffffffffda RBX: 00005561dc02eca0 RCX: 00007ffbc0ded307 > [ 157.296185] RDX: 0000000000000241 RSI: 00005561dc013470 RDI: 00000000ffffff9c > [ 157.303317] RBP: 00005561dc013470 R08: 0000000000000004 R09: 0000000000000001 > [ 157.310447] R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000241 > [ 157.317575] R13: 00005561dc02eca0 R14: 0000000000000001 R15: 0000000000000000 > [ 157.324705] Modules linked in: isst_if_common squashfs nls_iso8859_1 nls_cp437 snd_hda_codec_realtek vfat snd_hda_codec_generic fat iwlmvm ledtrig_audio snd_hda_codec_hdmi x86_pkg_temp_thermal intel_powerclamp snd_hda_intel snd_intel_dspcfg iwlwifi efi_pstore btusb snd_hda_codec btrtl btbcm efivars snd_hwdep btintel snd_hda_core iTCO_wdt iTCO_vendor_support mei_me mei loop coretemp hid_logitech_hidpp hid_logitech_dj hid_lenovo amdgpu gpu_sched i40e ixgbe ast drm_vram_helper drm_ttm_helper ttm mdio xhci_pci xhci_hcd > [ 157.370249] CR2: 0000000000000020 > > There's a lot more of these later, some interspersed (possibly related > to grabbing the output via serial->bmc->network->ipmitool). I've > attached the whole dmesg and .config. > > What would be helpful for debugging? Should I try the v5 branch instead? > > I'll try setting up a VM + passing through NVME to be able to test this > without fear... In one instance I did see some minor corruption on > another device & fs (ext4 on dm-crypt on nvme). It's all backed up, > but... I have a known issue with request starvation, wonder if that could be it. I'm going to rebase the branch on top of the aops->readahead() changes shortly, and fix that issue. Hopefully that's what's plaguing your run here, but if not, I'll hunt that one down. Thanks for testing! -- Jens Axboe