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=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 62FD6C433B4 for ; Wed, 14 Apr 2021 13:59:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 34BB96113D for ; Wed, 14 Apr 2021 13:59:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351770AbhDNN7e (ORCPT ); Wed, 14 Apr 2021 09:59:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349256AbhDNN7b (ORCPT ); Wed, 14 Apr 2021 09:59:31 -0400 Received: from mail-qv1-xf2d.google.com (mail-qv1-xf2d.google.com [IPv6:2607:f8b0:4864:20::f2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35DCDC061574 for ; Wed, 14 Apr 2021 06:59:10 -0700 (PDT) Received: by mail-qv1-xf2d.google.com with SMTP id dp18so5257259qvb.5 for ; Wed, 14 Apr 2021 06:59:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=from:references:in-reply-to:mime-version:thread-index:date :message-id:subject:to:cc; bh=6r9JwOVALllemG/KZpFYZ890CpHBTKvGkm/N0RAA4G8=; b=TwIlfcyFBsYIyKzAbGvvayNp0ebIZEMurcwrAlDTcmfq8dk2R8FTTtAM654ZfEXSq4 6ybkUUzdQEN478YZOrx5GxUfURMtlaEy9PpD/xu8S8z5mukNlfMqf6ZxVYtKQ3+hUSc+ TMTwYOojMYWrJiakhekFk1yTJYTIfHLuaWSP0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:references:in-reply-to:mime-version :thread-index:date:message-id:subject:to:cc; bh=6r9JwOVALllemG/KZpFYZ890CpHBTKvGkm/N0RAA4G8=; b=XWUXKXvyg63FIBAiGbzxMwBLDSFvv2sgAcP0gaZuaDfBXBhG5cZzuqGcpF2tlhKglQ BFSeJfU+IQFWED76yLqj2ULMCviJsjKjh3+IhAjkRiFgK08tFODY+8BHP73kkkMu0Pdl VKOKgbPvoIwT1dfRqWs39ArMNgbQ5jrfLtUFZOBg9bC1qpEYHUaSGBMQOdMALwggXt9F M3CJ2RDHKZB+GM1OmHfPEVt0YMqLLJQTe3z5xvSMlamJjt8mNioRd6fh25UwDalBrefm PkcIvhSwZL64lXN0AcAEl10b4cpLkFYPrpfvTwUm8WySSWp9NrEX8R/2WK1hV7OLYtTn 4U0g== X-Gm-Message-State: AOAM532LgAu6m/RBtfmezGuSjILxM5v+fPjETyNqp0YuyR2knxMrsFZk tu9QYcBWuHoB5mvcBm3Ny6P4HbkVL6374SZXjy3E5w== X-Google-Smtp-Source: ABdhPJySIQ6dEH9/1rs6FkRfcCSDDlu8j1m1IGcDm7vrnIlk/9pCZ1nO+a45CO7V2pKHBIkMr7pghPIP2+gRTEftjaI= X-Received: by 2002:a0c:fa8e:: with SMTP id o14mr3451204qvn.45.1618408749257; Wed, 14 Apr 2021 06:59:09 -0700 (PDT) From: Kashyap Desai References: <9a6145a5-e6ac-3d33-b52a-0823bfc3b864@huawei.com> In-Reply-To: MIME-Version: 1.0 X-Mailer: Microsoft Outlook 15.0 Thread-Index: AQHvM4xIklkXT4m1nLiQOVtWtLHGaQF/MHX/AdTL8DQCJZY+sapYNahw Date: Wed, 14 Apr 2021 19:29:07 +0530 Message-ID: Subject: RE: [bug report] shared tags causes IO hang and performance drop To: Ming Lei Cc: John Garry , linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, "Martin K. Petersen" , Jens Axboe , Douglas Gilbert Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="000000000000a02c2f05bfef26b1" Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org --000000000000a02c2f05bfef26b1 Content-Type: text/plain; charset="UTF-8" > > I tried both - 5.12.0-rc1 and 5.11.0-rc2+ and there is a same behavior. > > Let me also check megaraid_sas and see if anything generic or this is > > a special case of scsi_debug. > > As I mentioned, it could be one generic issue wrt. SCHED_RESTART. > shared tags might have to restart all hctx since all share same tags. Ming - I tried many combination on MR shared host tag driver but there is no single instance of IO hang. I will keep trying, but when I look at scsi_debug driver code I found below odd settings in scsi_debug driver. can_queue of adapter is set to 128 but queue_depth of sdev is set to 255. If I apply below patch, scsi_debug driver's hang is also resolved. Ideally sdev->queue depth cannot exceed shost->can_queue. Not sure why cmd_per_lun is 255 in scsi_debug driver which can easily exceed can_queue. I will simulate something similar in MR driver and see how it behaves w.r.t IO hang issue. diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c index 70165be10f00..dded762540ee 100644 --- a/drivers/scsi/scsi_debug.c +++ b/drivers/scsi/scsi_debug.c @@ -218,7 +218,7 @@ static const char *sdebug_version_date = "20200710"; */ #define SDEBUG_CANQUEUE_WORDS 3 /* a WORD is bits in a long */ #define SDEBUG_CANQUEUE (SDEBUG_CANQUEUE_WORDS * BITS_PER_LONG) -#define DEF_CMD_PER_LUN 255 +#define DEF_CMD_PER_LUN SDEBUG_CANQUEUE /* UA - Unit Attention; SA - Service Action; SSU - Start Stop Unit */ #define F_D_IN 1 /* Data-in command (e.g. READ) */ @@ -7558,6 +7558,7 @@ static int sdebug_driver_probe(struct device *dev) sdbg_host = to_sdebug_host(dev); sdebug_driver_template.can_queue = sdebug_max_queue; + sdebug_driver_template.cmd_per_lun = sdebug_max_queue; if (!sdebug_clustering) sdebug_driver_template.dma_boundary = PAGE_SIZE - 1; > > > Thanks, > Ming --000000000000a02c2f05bfef26b1 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