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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A1225C19F2A for ; Thu, 4 Aug 2022 14:22:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238146AbiHDOWa (ORCPT ); Thu, 4 Aug 2022 10:22:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231232AbiHDOW2 (ORCPT ); Thu, 4 Aug 2022 10:22:28 -0400 Received: from alexa-out-sd-02.qualcomm.com (alexa-out-sd-02.qualcomm.com [199.106.114.39]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B77F11F2E7; Thu, 4 Aug 2022 07:22:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1659622947; x=1691158947; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=XGxaOPSSf/dYHdHGXWUvW+HF+yIBOA1VfLwIE2nD8Nw=; b=TxlR0P9K9BWavG85g5buFpteRzp600Z7rxgNg8zTp/wnxR1Zka2Xi3oI TYZargKqLFCIzR08I0RokdZxbNKb3eaVcEm/83P4ihN1Z0cS6fceUwjO8 KO5RJEFyFwWXWTAiV3sQXM0+QABSICb1Gn+wGh1z92d/Rq1gC79Vta+OX Y=; Received: from unknown (HELO ironmsg05-sd.qualcomm.com) ([10.53.140.145]) by alexa-out-sd-02.qualcomm.com with ESMTP; 04 Aug 2022 07:22:27 -0700 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg05-sd.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Aug 2022 07:22:26 -0700 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22; Thu, 4 Aug 2022 07:22:26 -0700 Received: from [10.226.59.182] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.22; Thu, 4 Aug 2022 07:22:25 -0700 Message-ID: <0f19cc67-ccb1-7cd1-5475-d2ec0e1abfc0@quicinc.com> Date: Thu, 4 Aug 2022 08:22:24 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.0 Subject: Re: [PATCH] PCI: hv: Only reuse existing IRTE allocation for Multi-MSI Content-Language: en-US To: , , , , , , , , , , , , , , , , CC: Carl Vanderlip References: <20220804025104.15673-1-decui@microsoft.com> From: Jeffrey Hugo In-Reply-To: <20220804025104.15673-1-decui@microsoft.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On 8/3/2022 8:51 PM, Dexuan Cui wrote: > Jeffrey's 4 recent patches added Multi-MSI support to the pci-hyperv driver. > Unluckily, one of the patches, i.e., b4b77778ecc5, causes a regression to a > fio test for the Azure VM SKU Standard L64s v2 (64 AMD vCPUs, 8 NVMe drives): > > when fio runs against all the 8 NVMe drives, it runs fine with a low io-depth > (e.g., 2 or 4); when fio runs with a high io-depth (e.g., 256), somehow > queue-29 of each NVMe drive suddenly no longer receives any interrupts, and > the NVMe core code has to abort the queue after a timeout of 30 seconds, and > then queue-29 starts to receive interrupts again for several seconds, and > later queue-29 no longer receives interrupts again, and this pattern repeats: > > [ 223.891249] nvme nvme2: I/O 320 QID 29 timeout, aborting > [ 223.896231] nvme nvme0: I/O 320 QID 29 timeout, aborting > [ 223.898340] nvme nvme4: I/O 832 QID 29 timeout, aborting > [ 259.471309] nvme nvme2: I/O 320 QID 29 timeout, aborting > [ 259.476493] nvme nvme0: I/O 321 QID 29 timeout, aborting > [ 259.482967] nvme nvme0: I/O 322 QID 29 timeout, aborting > > Some other symptoms are: the throughput of the NVMe drives drops due to > commit b4b77778ecc5. When the fio test is running, the kernel prints some > soft lock-up messages from time to time. > > Commit b4b77778ecc5 itself looks good, and at the moment it's unclear where > the issue is. While the issue is being investigated, restore the old behavior > in hv_compose_msi_msg(), i.e., don't reuse the existing IRTE allocation for > single-MSI and MSI-X. This is a stopgap for the above NVMe issue. > > Fixes: b4b77778ecc5 ("PCI: hv: Reuse existing IRTE allocation in compose_msi_msg()") > Signed-off-by: Dexuan Cui > Cc: Jeffrey Hugo > Cc: Carl Vanderlip > --- I'm sorry a regression has been discovered. Right now, the issue doesn't make sense to me. I'd love to know what you find out. This stopgap solution appears reasonable to me. Reviewed-by: Jeffrey Hugo