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=-6.9 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 autolearn=unavailable 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 B8889C433DF for ; Thu, 4 Jun 2020 08:59:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91E212074B for ; Thu, 4 Jun 2020 08:59:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="K2fjP8ko" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728237AbgFDI7d (ORCPT ); Thu, 4 Jun 2020 04:59:33 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:32646 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726923AbgFDI7c (ORCPT ); Thu, 4 Jun 2020 04:59:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1591261169; 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=WtpcAxuXjKPd+xNwjjUSXh6QNnhLy+bQzZ28Gv1mh5o=; b=K2fjP8koRi/mDx9Rx0VbKt0KVuea1h/Ql/59SGD65d5Yxs1nRT3Ztg45bwuRZuUVBLhV8y vwnplek9Ak4lviCK1B8iPXQ//DgA57q+yFRAOwykUcbpGPjP+Q5gcK7D+kLwzZwixsj1Hg 4yCgDYJ0/VyaXPHLNwCV3/qlOrBAY+M= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-145-ShVdGubiNG6_lEYQHGK6rg-1; Thu, 04 Jun 2020 04:59:28 -0400 X-MC-Unique: ShVdGubiNG6_lEYQHGK6rg-1 Received: by mail-wr1-f69.google.com with SMTP id z10so2160975wrs.2 for ; Thu, 04 Jun 2020 01:59:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=WtpcAxuXjKPd+xNwjjUSXh6QNnhLy+bQzZ28Gv1mh5o=; b=dAjPrZUW6zcgCp/30phcxWOtu5Fc1guSZZ7ThKjZy+vEffLqcts5Pde0t0O6iXxDJ1 ryLjzrRT4M6qzKE4NpU+PdkXsPudviSpWC39gnoZ15yA5er/u8r6v8d9Rkao2JapPIgY 5+FO3DTU303DA5BZYedM2uoQy8HQhahKFhaV2bJWVxYxzsAYY5tT697Tg+NNEYfpoKME AhJddUG97R05uPGD0t9up3w0ZB7VO0dwvnP/VJpdU7Y12iohoYk7eIMcH727Ka0DRpt7 +xGa+a6YAZ8kyU8N+070czBoTuqU6keIME9reUHUA5qAVTl7/K3csLwTR40YvjGVhzij OslQ== X-Gm-Message-State: AOAM532CirSS1BM0BvXVFXOdFpHqEg1AY0lbbjxQiq7Aavam6lUl+rJo J2SC1MVNdpNd07pfGAjci+92EIdQ/U8UDHk7MuLx4JXqlEBJ6UOxBa2vGeA9deekjE1wxvo26kJ 3lVx3eS6stPgXwa/P X-Received: by 2002:a7b:cd83:: with SMTP id y3mr2969358wmj.5.1591261166632; Thu, 04 Jun 2020 01:59:26 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyQVYOhaYqCqR2g6yBIim1YuvVtyZyB4PwbWTMfxoV4tzCD7LBQh4YsXfIK4thbfTeY+Hcx7Q== X-Received: by 2002:a7b:cd83:: with SMTP id y3mr2969335wmj.5.1591261166347; Thu, 04 Jun 2020 01:59:26 -0700 (PDT) Received: from redhat.com ([2a00:a040:185:f65:9a3b:8fff:fed3:ad8d]) by smtp.gmail.com with ESMTPSA id h12sm6760861wro.80.2020.06.04.01.59.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jun 2020 01:59:25 -0700 (PDT) Date: Thu, 4 Jun 2020 04:59:22 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: linux-kernel@vger.kernel.org, Eugenio =?iso-8859-1?Q?P=E9rez?= , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH RFC 03/13] vhost: batching fetches Message-ID: <20200604045830-mutt-send-email-mst@kernel.org> References: <20200602130543.578420-1-mst@redhat.com> <20200602130543.578420-4-mst@redhat.com> <3323daa2-19ed-02de-0ff7-ab150f949fff@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3323daa2-19ed-02de-0ff7-ab150f949fff@redhat.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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. > > + > > static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) > > { > > kfree(vq->descs); > > @@ -389,6 +395,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) > > for (i = 0; i < dev->nvqs; ++i) { > > vq = dev->vqs[i]; > > vq->max_descs = dev->iov_limit; > > + if (vhost_vq_num_batch_descs(vq) < 0) { > > + return -EINVAL; > > + } > > vq->descs = kmalloc_array(vq->max_descs, > > sizeof(*vq->descs), > > GFP_KERNEL); > > @@ -1570,6 +1579,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > > vq->last_avail_idx = s.num; > > /* Forget the cached index value. */ > > vq->avail_idx = vq->last_avail_idx; > > + vq->ndescs = vq->first_desc = 0; > > break; > > case VHOST_GET_VRING_BASE: > > s.index = idx; > > @@ -2136,7 +2146,7 @@ static int fetch_indirect_descs(struct vhost_virtqueue *vq, > > return 0; > > } > > -static int fetch_descs(struct vhost_virtqueue *vq) > > +static int fetch_buf(struct vhost_virtqueue *vq) > > { > > unsigned int i, head, found = 0; > > struct vhost_desc *last; > > @@ -2149,7 +2159,11 @@ static int fetch_descs(struct vhost_virtqueue *vq) > > /* Check it isn't doing very strange things with descriptor numbers. */ > > last_avail_idx = vq->last_avail_idx; > > - if (vq->avail_idx == vq->last_avail_idx) { > > + if (unlikely(vq->avail_idx == vq->last_avail_idx)) { > > + /* If we already have work to do, don't bother re-checking. */ > > + if (likely(vq->ndescs)) > > + return vq->num; > > + > > if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { > > vq_err(vq, "Failed to access avail idx at %p\n", > > &vq->avail->idx); > > @@ -2240,6 +2254,24 @@ static int fetch_descs(struct vhost_virtqueue *vq) > > return 0; > > } > > +static int fetch_descs(struct vhost_virtqueue *vq) > > +{ > > + int ret = 0; > > + > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > + vq->first_desc = 0; > > + vq->ndescs = 0; > > + } > > + > > + if (vq->ndescs) > > + return 0; > > + > > + while (!ret && vq->ndescs <= vhost_vq_num_batch_descs(vq)) > > + ret = fetch_buf(vq); > > + > > + return vq->ndescs ? 0 : ret; > > +} > > + > > /* This looks in the virtqueue and for the first available buffer, and converts > > * it to an iovec for convenient access. Since descriptors consist of some > > * number of output then some number of input descriptors, it's actually two > > @@ -2265,7 +2297,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, > > if (unlikely(log)) > > *log_num = 0; > > - for (i = 0; i < vq->ndescs; ++i) { > > + for (i = vq->first_desc; i < vq->ndescs; ++i) { > > unsigned iov_count = *in_num + *out_num; > > struct vhost_desc *desc = &vq->descs[i]; > > int access; > > @@ -2311,14 +2343,19 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, > > } > > ret = desc->id; > > + > > + if (!(desc->flags & VRING_DESC_F_NEXT)) > > + break; > > } > > - vq->ndescs = 0; > > + vq->first_desc = i + 1; > > return ret; > > err: > > - vhost_discard_vq_desc(vq, 1); > > + for (i = vq->first_desc; i < vq->ndescs; ++i) > > + if (!(vq->descs[i].flags & VRING_DESC_F_NEXT)) > > + vhost_discard_vq_desc(vq, 1); > > vq->ndescs = 0; > > return ret; > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > index 76356edee8e5..a67bda9792ec 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -81,6 +81,7 @@ struct vhost_virtqueue { > > struct vhost_desc *descs; > > int ndescs; > > + int first_desc; > > int max_descs; > > struct file *kick; > > @@ -229,7 +230,7 @@ void vhost_iotlb_map_free(struct vhost_iotlb *iotlb, > > struct vhost_iotlb_map *map); > > #define vq_err(vq, fmt, ...) do { \ > > - pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \ > > + pr_err(pr_fmt(fmt), ##__VA_ARGS__); \ > > > Need a separate patch for this? > > Thanks Oh that's a debugging thing. I will drop it. > > > if ((vq)->error_ctx) \ > > eventfd_signal((vq)->error_ctx, 1);\ > > } while (0) > > @@ -255,6 +256,8 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, > > void *private_data) > > { > > vq->private_data = private_data; > > + vq->ndescs = 0; > > + vq->first_desc = 0; > > } > > /**