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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,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 2B637C47095 for ; Wed, 9 Jun 2021 06:12:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A40261278 for ; Wed, 9 Jun 2021 06:12:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231258AbhFIGOm (ORCPT ); Wed, 9 Jun 2021 02:14:42 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42633 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230353AbhFIGOm (ORCPT ); Wed, 9 Jun 2021 02:14:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623219167; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wsM4h3EkGEQmgmsNgnC2R5LoMvPDTkfK4KK+tHDX7DY=; b=jREiR5MLg6e/khI1QMCftYjm+3h0ZTQO955e3RoFDWMGtOq9g61PdAigRefYqjxtaErRR3 bLEu7qH9I//M36mQ/mstE6gqEEoTfbnNanb7ml9JO9qsowFjQ0Pxq5uwmLEOiS9TxH9up+ muKX80lJ4bNfllUsuw4D9RiDALb2YGI= 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-428-n1pWRk-7On6jWsatSSV6uw-1; Wed, 09 Jun 2021 02:12:44 -0400 X-MC-Unique: n1pWRk-7On6jWsatSSV6uw-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 69B3E801106; Wed, 9 Jun 2021 06:12:43 +0000 (UTC) Received: from T590 (ovpn-12-143.pek2.redhat.com [10.72.12.143]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3F64260C04; Wed, 9 Jun 2021 06:12:36 +0000 (UTC) Date: Wed, 9 Jun 2021 14:12:32 +0800 From: Ming Lei To: Wang Shanker Cc: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org Subject: Re: [PATCH 2/2] block: support bio merge for multi-range discard Message-ID: References: <20210609004556.46928-1-ming.lei@redhat.com> <20210609004556.46928-3-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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, Jun 09, 2021 at 11:05:59AM +0800, Wang Shanker wrote: > > > > 2021年06月09日 08:45，Ming Lei 写道： > > > > So far multi-range discard treats each bio as one segment(range) of single > > discard request. This way becomes not efficient if lots of small sized > > discard bios are submitted, and one example is raid456. > > > > Support bio merge for multi-range discard for improving lots of small > > sized discard bios. > > > > Turns out it is easy to support it: > > > > 1) always try to merge bio first > > > > 2) run into multi-range discard only if bio merge can't be done > > > > 3) add rq_for_each_discard_range() for retrieving each range(segment) > > of discard request > > > > Reported-by: Wang Shanker > > Signed-off-by: Ming Lei > > --- > > block/blk-merge.c | 12 ++++----- > > drivers/block/virtio_blk.c | 9 ++++--- > > drivers/nvme/host/core.c | 8 +++--- > > include/linux/blkdev.h | 51 ++++++++++++++++++++++++++++++++++++++ > > 4 files changed, 66 insertions(+), 14 deletions(-) > > > > diff --git a/block/blk-merge.c b/block/blk-merge.c > > index bcdff1879c34..65210e9a8efa 100644 > > --- a/block/blk-merge.c > > +++ b/block/blk-merge.c > > @@ -724,10 +724,10 @@ static inline bool blk_discard_mergable(struct request *req) > > static enum elv_merge blk_try_req_merge(struct request *req, > > struct request *next) > > { > > - if (blk_discard_mergable(req)) > > - return ELEVATOR_DISCARD_MERGE; > > - else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) > > + if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) > > return ELEVATOR_BACK_MERGE; > > + else if (blk_discard_mergable(req)) > > Shall we adjust how req->nr_phys_segments is calculated in > bio_attempt_discard_merge() so that multiple contiguous bio's can > be seen as one segment? I think it isn't necessary, because we try to merge discard IOs first just like plain IO. So when bio_attempt_discard_merge() is reached, it means that IOs can't be merged, so req->nr_phys_segments should be increased by 1. Thanks, Ming