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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 8EDF8C433DF for ; Fri, 5 Jun 2020 03:40:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63A38206DB for ; Fri, 5 Jun 2020 03:40:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bMinaiap" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728407AbgFEDk2 (ORCPT ); Thu, 4 Jun 2020 23:40:28 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:28087 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726076AbgFEDk2 (ORCPT ); Thu, 4 Jun 2020 23:40:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591328426; 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=W+XRm7Fs7zNlH2EKv4SYh8NMSzGAObCRW7/zCrf8kTM=; b=bMinaiappCB0rQc0Seywa3/cVkuzqVzgZOHZhSWQYCSkZ81iRslS8kNSRBSGKgQPcCx3Eu gHHK9CiCuq2raB5URMZCpac6lqycim7AIT742YFDBVZhE+poHPc5vekg0QfB/DIc6sNCgl vs8r/qfW+iKVf6IEabXSwJEbgFg5uds= 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-257-WjnfLQgyPAadytx9KbfT2Q-1; Thu, 04 Jun 2020 23:40:24 -0400 X-MC-Unique: WjnfLQgyPAadytx9KbfT2Q-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AD756100960F; Fri, 5 Jun 2020 03:40:23 +0000 (UTC) Received: from [10.72.12.233] (ovpn-12-233.pek2.redhat.com [10.72.12.233]) by smtp.corp.redhat.com (Postfix) with ESMTP id D3AE45C290; Fri, 5 Jun 2020 03:40:18 +0000 (UTC) Subject: Re: [PATCH RFC 03/13] vhost: batching fetches To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, =?UTF-8?Q?Eugenio_P=c3=a9rez?= , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org References: <20200602130543.578420-1-mst@redhat.com> <20200602130543.578420-4-mst@redhat.com> <3323daa2-19ed-02de-0ff7-ab150f949fff@redhat.com> <20200604045830-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <6c2e6cc7-27c5-445b-f252-0356ff8a83f3@redhat.com> Date: Fri, 5 Jun 2020 11:40:17 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200604045830-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/6/4 下午4:59, Michael S. Tsirkin wrote: > On Wed, Jun 03, 2020 at 03:27:39PM +0800, Jason Wang wrote: >> On 2020/6/2 下午9:06, Michael S. Tsirkin wrote: >>> With this patch applied, new and old code perform identically. >>> >>> Lots of extra optimizations are now possible, e.g. >>> we can fetch multiple heads with copy_from/to_user now. >>> We can get rid of maintaining the log array. Etc etc. >>> >>> Signed-off-by: Michael S. Tsirkin >>> Signed-off-by: Eugenio Pérez >>> Link:https://lore.kernel.org/r/20200401183118.8334-4-eperezma@redhat.com >>> Signed-off-by: Michael S. Tsirkin >>> --- >>> drivers/vhost/test.c | 2 +- >>> drivers/vhost/vhost.c | 47 ++++++++++++++++++++++++++++++++++++++----- >>> drivers/vhost/vhost.h | 5 ++++- >>> 3 files changed, 47 insertions(+), 7 deletions(-) >>> >>> diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c >>> index 9a3a09005e03..02806d6f84ef 100644 >>> --- a/drivers/vhost/test.c >>> +++ b/drivers/vhost/test.c >>> @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) >>> dev = &n->dev; >>> vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; >>> n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; >>> - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, >>> + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, >>> VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, NULL); >>> f->private_data = n; >>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >>> index 8f9a07282625..aca2a5b0d078 100644 >>> --- a/drivers/vhost/vhost.c >>> +++ b/drivers/vhost/vhost.c >>> @@ -299,6 +299,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, >>> { >>> vq->num = 1; >>> vq->ndescs = 0; >>> + vq->first_desc = 0; >>> vq->desc = NULL; >>> vq->avail = NULL; >>> vq->used = NULL; >>> @@ -367,6 +368,11 @@ static int vhost_worker(void *data) >>> return 0; >>> } >>> +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) >>> +{ >>> + return vq->max_descs - UIO_MAXIOV; >>> +} >> 1 descriptor does not mean 1 iov, e.g userspace may pass several 1 byte >> length memory regions for us to translate. >> > Yes but I don't see the relevance. This tells us how many descriptors to > batch, not how many IOVs. Yes, but questions are: - this introduce another obstacle to support more than 1K queue size - if we support 1K queue size, does it mean we need to cache 1K descriptors, which seems a large stress on the cache Thanks >