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=-7.1 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,URIBL_BLOCKED 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 C0880C433DF for ; Tue, 21 Jul 2020 06:53:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BD1120B1F for ; Tue, 21 Jul 2020 06:53:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=broadcom.com header.i=@broadcom.com header.b="bK8YIY79" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728117AbgGUGxn (ORCPT ); Tue, 21 Jul 2020 02:53:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726698AbgGUGxm (ORCPT ); Tue, 21 Jul 2020 02:53:42 -0400 Received: from mail-qt1-x844.google.com (mail-qt1-x844.google.com [IPv6:2607:f8b0:4864:20::844]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 268BAC061794 for ; Mon, 20 Jul 2020 23:53:42 -0700 (PDT) Received: by mail-qt1-x844.google.com with SMTP id e12so15370150qtr.9 for ; Mon, 20 Jul 2020 23:53:42 -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=/LzX205OrVJxpDVgD3okbRlxqqEZJ1kZvD6gwUPc6+w=; b=bK8YIY79uozJq8nAajqEK227dyxwk/ewc+lSm4zEJp4hFMrzvVBAK/UStdfJGz8pK/ xfex1nbbbqNWdolykGggSOqmlvMLGr6bVnUFALah9O0qn0S2CX/mdfV5PrICYAYYhjwv T1rgXpyCIhEo6ihcdRPCMVt+6nFBEuLxj/F04= 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=/LzX205OrVJxpDVgD3okbRlxqqEZJ1kZvD6gwUPc6+w=; b=MeuMpHD5gOQyjiHyUD2xLjSfyvknMmvvRd+V0NbGIICXq9Uf0b2sdMo3yNb2H1yrav yysBtwj05XvqYrDMcR/CfxFNt6c2wG1eWdW10mhUd/900ZDOPgfL13IFJSrznOpXlyuZ PbkjbaoZSmMHQrp+WO7TpZNBCD+uh+xfzXHQAebzrmd/25oi+I5krOdB+CfI2pPM1JWR gDDnB8I14zoVCD1A6TbSb9BK+2SGrDe9Cps4KY3ZFnjwPg1/xn7entY5q3ypVoBzBQx3 Jr5g++HzeF1MpOriz32IykiMLjU212vXOMhMSvrDv/PSPOnoWMc6UodrjkxWJvlrsGpm VIUg== X-Gm-Message-State: AOAM531UvUw2vSwhOlx/8e6gvcbmKfqZaRnYvTR6SbI8NAzCShN2X5SJ ywMcx7oheFzQ0KZyJoNbck2BnAJqljLlkS7HK4/3tQ== X-Google-Smtp-Source: ABdhPJx9UIqbJmT3ciJpPn/RECvKEVWHhtsDZpKUoXVlcMNzMGiz5RapIvzx6yBFENi+j4pIIeS78ePC4YigAXjBNo0= X-Received: by 2002:ac8:36bb:: with SMTP id a56mr27509911qtc.201.1595314421244; Mon, 20 Jul 2020 23:53:41 -0700 (PDT) From: Kashyap Desai References: <92ba1829c9e822e4239a7cdfd94acbce@mail.gmail.com> <10d36c09-9d5b-92e9-23ac-ea1a2628e7d9@huawei.com> <0563e53f843c97de1a5a035fae892bf8@mail.gmail.com> <61299951-97dc-b2be-c66c-024dfbd3a1cb@huawei.com> <13d6b63e-3aa8-68fa-29ab-a4c202024280@huawei.com> <34a832717fef4702b143ea21aa12b79e@mail.gmail.com> <1dcf2bb9-142c-7bb8-9207-5a1b792eb3f9@huawei.com> <20200721011323.GA833377@T590> In-Reply-To: <20200721011323.GA833377@T590> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 15.0 Thread-Index: AQGYVoTUA+B9zIZNqWv71qXbwKlkDwGZowweAlKrFcUB/hGY5AG4aoXNAvsHUMYCeW9VQwH6WrIOAzKzW+wCpzQ5OANTX/rUqMuvaHA= Date: Tue, 21 Jul 2020 12:23:39 +0530 Message-ID: Subject: RE: [PATCH RFC v7 10/12] megaraid_sas: switch fusion adapters to MQ To: Ming Lei Cc: John Garry , axboe@kernel.dk, jejb@linux.ibm.com, martin.petersen@oracle.com, don.brace@microsemi.com, Sumit Saxena , bvanassche@acm.org, hare@suse.com, hch@lst.de, Shivasharan Srikanteshwara , linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, esc.storagedev@microsemi.com, chenxiang66@hisilicon.com, "PDL,MEGARAIDLINUX" Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org > > > > > > Perf top (shared host tag. IOPS = 230K) > > > > > > 13.98% [kernel] [k] sbitmap_any_bit_set > > > 6.43% [kernel] [k] blk_mq_run_hw_queue > > > > blk_mq_run_hw_queue function take more CPU which is called from " > > scsi_end_request" > > The problem could be that nr_hw_queues is increased a lot so that sample on > blk_mq_run_hw_queue() can be observed now. Yes. That is correct. > > > It looks like " blk_mq_hctx_has_pending" handles only elevator > > (scheduler) case. If queue has ioscheduler=none, we can skip. I case > > of scheduler=none, IO will be pushed to hardware queue and it by pass > software queue. > > Based on above understanding, I added below patch and I can see > > performance scale back to expectation. > > > > Ming mentioned that - we cannot remove blk_mq_run_hw_queues() from IO > > completion path otherwise we may see IO hang. So I have just modified > > completion path assuming it is only required for IO scheduler case. > > https://www.spinics.net/lists/linux-block/msg55049.html > > > > Please review and let me know if this is good or we have to address > > with proper fix. > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c index > > 1be7ac5a4040..b6a5b41b7fc2 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -1559,6 +1559,9 @@ void blk_mq_run_hw_queues(struct > request_queue > > *q, bool async) > > struct blk_mq_hw_ctx *hctx; > > int i; > > > > + if (!q->elevator) > > + return; > > + > > This way shouldn't be correct, blk_mq_run_hw_queues() is still needed for > none because request may not be dispatched successfully by direct issue. When block layer attempt posting request to h/w queue directly (for ioscheduler=none) and if it fails, it is calling blk_mq_request_bypass_insert(). blk_mq_request_bypass_insert function will start the h/w queue from submission context. Do we still have an issue if we skip running hw queue from completion ? Kashyap > > > Thanks, > Ming