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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9A983C54EBE for ; Fri, 13 Jan 2023 11:46:02 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pGIUh-0006Xq-7Y; Fri, 13 Jan 2023 06:45:11 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pGIUd-0006XW-Nh for qemu-devel@nongnu.org; Fri, 13 Jan 2023 06:45:07 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pGIUb-0003ea-OC for qemu-devel@nongnu.org; Fri, 13 Jan 2023 06:45:07 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673610304; 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=TDeC/q9e/O2TdDj+PE5/t+nBZE0Vk5iCcYjhDCuMkrY=; b=iJ6hNc8+6HtXdDVMkEc1njHcJaIFYINLEdkVWxhbjw89yu7YdxnHo23driC/GATP9+NEV8 h68/NQuwhdJSNgGDeUdBje6qWYKrLI1JP+G7f81/w7CGe3MnVq9untQsnAkzQ+FpJgPr4N FO0F9o8WYiC4eaQCgQ7DZuN83+qSbTM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-300-JCBhxcfSPXCTVksdje4wPw-1; Fri, 13 Jan 2023 06:45:01 -0500 X-MC-Unique: JCBhxcfSPXCTVksdje4wPw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 83DC7858F0E; Fri, 13 Jan 2023 11:45:00 +0000 (UTC) Received: from redhat.com (unknown [10.39.195.6]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0D5E6492B00; Fri, 13 Jan 2023 11:44:58 +0000 (UTC) Date: Fri, 13 Jan 2023 12:44:57 +0100 From: Kevin Wolf To: Ilya Dryomov Cc: Or Ozeri , qemu-devel@nongnu.org, dupadhya@redhat.com, to.my.trociny@gmail.com, qemu-block@nongnu.org, dannyh@il.ibm.com, Stefan Hajnoczi , pbonzini@redhat.com Subject: Re: [PATCH v1 1/1] virtio-block: switch to blk_get_max_hw_transfer Message-ID: References: <20211209092815.778066-1-oro@il.ibm.com> <20211209092815.778066-2-oro@il.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 12.01.2023 um 21:28 hat Ilya Dryomov geschrieben: > On Thu, Dec 9, 2021 at 10:34 AM Or Ozeri wrote: > > > > The blk_get_max_hw_transfer API was recently added in 6.1.0. > > It allows querying an underlying block device its max transfer capability. > > This commit changes virtio-blk to use this. > > > > Signed-off-by: Or Ozeri > > --- > > hw/block/virtio-blk.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > > index f139cd7cc9..1ba9a06888 100644 > > --- a/hw/block/virtio-blk.c > > +++ b/hw/block/virtio-blk.c > > @@ -458,7 +458,7 @@ static void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb) > > return; > > } > > > > - max_transfer = blk_get_max_transfer(mrb->reqs[0]->dev->blk); > > + max_transfer = blk_get_max_hw_transfer(mrb->reqs[0]->dev->blk); > > > > qsort(mrb->reqs, mrb->num_reqs, sizeof(*mrb->reqs), > > &multireq_compare); > > Hi Or, > > Superficially, this makes sense to me. I'm not sure I understand. This is not a passthrough device (unlike scsi-generic), so why should we consider the hardware limits rather than the kernel/other backend limits for read/write requests? See the documentation of both fields: /* * Maximal transfer length in bytes. Need not be power of 2, but * must be multiple of opt_transfer and bl.request_alignment, or 0 * for no 32-bit limit. For now, anything larger than INT_MAX is * clamped down. */ uint32_t max_transfer; /* * Maximal hardware transfer length in bytes. Applies whenever * transfers to the device bypass the kernel I/O scheduler, for * example with SG_IO. If larger than max_transfer or if zero, * blk_get_max_hw_transfer will fall back to max_transfer. */ uint64_t max_hw_transfer; Is the real problem that max_transfer isn't right? Kevin