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_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,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 670B7C433B4 for ; Wed, 7 Apr 2021 10:15:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 387306139C for ; Wed, 7 Apr 2021 10:15:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350769AbhDGKPf (ORCPT ); Wed, 7 Apr 2021 06:15:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:28939 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235774AbhDGKP3 (ORCPT ); Wed, 7 Apr 2021 06:15:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617790469; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tpWdJceqZi+vDccG7bvsZkCK5+mYmOOPU4eTEgJFV74=; b=BMdrLvVYUDU0dMx67/w98q396S14UhVdaX7EPv/ebwO5T0nTk9A5D5X/9urnQ+LgC5AZWh GT5rgmisUGvKXvwDrxSQdB57RUMUOvssenJ1qhHEJxSbI4HoEwAj/aH5F8ji9rnm8U/VJz jJqRzRfXwO8hG7N4DcGA9ZbfHbWgwoI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-206-wLL_GZhYOHi1VCsLdZKw8A-1; Wed, 07 Apr 2021 06:14:26 -0400 X-MC-Unique: wLL_GZhYOHi1VCsLdZKw8A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 35F1B1856A60; Wed, 7 Apr 2021 10:14:25 +0000 (UTC) Received: from T590 (ovpn-12-31.pek2.redhat.com [10.72.12.31]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9864E610A8; Wed, 7 Apr 2021 10:14:18 +0000 (UTC) Date: Wed, 7 Apr 2021 18:14:13 +0800 From: Ming Lei To: John Garry Cc: Jens Axboe , linux-block@vger.kernel.org, Yanhui Ma , Hannes Reinecke , Kashyap Desai Subject: Re: [PATCH] blk-mq: set default elevator as deadline in case of hctx shared tagset Message-ID: References: <20210406031933.767228-1-ming.lei@redhat.com> <6c346805-a7b1-f66d-af16-b1da03d77fc0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6c346805-a7b1-f66d-af16-b1da03d77fc0@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Apr 07, 2021 at 09:04:30AM +0100, John Garry wrote: > Reviewed-by: John Garry > > > > On Tue, Apr 06, 2021 at 11:25:08PM +0100, John Garry wrote: > > > On 06/04/2021 04:19, Ming Lei wrote: > > > > > > Hi Ming, > > > > > > > Yanhui found that write performance is degraded a lot after applying > > > > hctx shared tagset on one test machine with megaraid_sas. And turns out > > > > it is caused by none scheduler which becomes default elevator caused by > > > > hctx shared tagset patchset. > > > > > > > > Given more scsi HBAs will apply hctx shared tagset, and the similar > > > > performance exists for them too. > > > > > > > > So keep previous behavior by still using default mq-deadline for queues > > > > which apply hctx shared tagset, just like before. > > > I think that there a some SCSI HBAs which have nr_hw_queues > 1 and don't > > > use shared sbitmap - do you think that they want want this as well (without > > > knowing it)? > > I don't know but none has been used for them since the beginning, so not > > an regression of shared tagset, but this one is really. > > It seems fine to revert to previous behavior when host_tagset is set. I > didn't check the results for this recently, but for the original shared > tagset patchset [0] I had: > > none sched: 2132K IOPS > mq-deadline sched: 2145K IOPS BTW, Yanhui reported that sequential write on virtio-scsi drops by 40~70% in VM, and the virito-scsi is backed by file image on XFS over megaraid_sas. And the disk is actually SSD, instead of HDD. It could be worse in case of megaraid_sas HDD. Same drop is observed on virtio-blk too. I didn't figure out one simple reproducer in host side yet, but the performance data is pretty stable in the VM IO workload. Thanks, Ming