From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Garzarella Subject: Re: [PATCH RFC 3/4] vsock/virtio: change the maximum packet size allowed Date: Fri, 5 Apr 2019 12:07:47 +0200 Message-ID: <20190405100747.dbwi3sjaudp3d2wa@steredhat> References: <20190404105838.101559-1-sgarzare@redhat.com> <20190404105838.101559-4-sgarzare@redhat.com> <20190405082447.GD25152@stefanha-x1.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, Jason Wang , "Michael S. Tsirkin" , Stefan Hajnoczi , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, "David S. Miller" To: Stefan Hajnoczi Return-path: Content-Disposition: inline In-Reply-To: <20190405082447.GD25152@stefanha-x1.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, Apr 05, 2019 at 09:24:47AM +0100, Stefan Hajnoczi wrote: > On Thu, Apr 04, 2019 at 12:58:37PM +0200, Stefano Garzarella wrote: > > Since now we are able to split packets, we can avoid limiting > > their sizes to VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE. > > Instead, we can use VIRTIO_VSOCK_MAX_PKT_BUF_SIZE as the max > > packet size. > > > > Signed-off-by: Stefano Garzarella > > --- > > net/vmw_vsock/virtio_transport_common.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > > index f32301d823f5..822e5d07a4ec 100644 > > --- a/net/vmw_vsock/virtio_transport_common.c > > +++ b/net/vmw_vsock/virtio_transport_common.c > > @@ -167,8 +167,8 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > > vvs = vsk->trans; > > > > /* we can send less than pkt_len bytes */ > > - if (pkt_len > VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE) > > - pkt_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE; > > + if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) > > + pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE; > > The next line limits pkt_len based on available credits: > > /* virtio_transport_get_credit might return less than pkt_len credit */ > pkt_len = virtio_transport_get_credit(vvs, pkt_len); > > I think drivers/vhost/vsock.c:vhost_transport_do_send_pkt() now works > correctly even with pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE. Correct. > > The other ->send_pkt() callback is > net/vmw_vsock/virtio_transport.c:virtio_transport_send_pkt_work() and it > can already send any size packet. > > Do you remember why VIRTIO_VSOCK_MAX_PKT_BUF_SIZE still needs to be the > limit? I'm wondering if we can get rid of it now and just limit packets > to the available credits. There are 2 reasons why I left this limit: 1. When the host receives a packets, it must be <= VIRTIO_VSOCK_MAX_PKT_BUF_SIZE [drivers/vhost/vsock.c:vhost_vsock_alloc_pkt()] So in this way we can limit the packets sent from the guest. 2. When the host send packets, it help us to increase the parallelism (especially if the guest has 64 KB RX buffers) because the user thread will split packets, calling multiple times transport->stream_enqueue() in net/vmw_vsock/af_vsock.c:vsock_stream_sendmsg() while the vhost_transport_send_pkt_work() send them to the guest. Do you think make sense? Thanks, Stefano 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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_NEOMUTT 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 2B0B8C4360F for ; Fri, 5 Apr 2019 10:07:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 04966217D4 for ; Fri, 5 Apr 2019 10:07:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730611AbfDEKHw (ORCPT ); Fri, 5 Apr 2019 06:07:52 -0400 Received: from mail-wm1-f66.google.com ([209.85.128.66]:36160 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729820AbfDEKHw (ORCPT ); Fri, 5 Apr 2019 06:07:52 -0400 Received: by mail-wm1-f66.google.com with SMTP id h18so6529766wml.1 for ; Fri, 05 Apr 2019 03:07:51 -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:in-reply-to:user-agent; bh=+/aW/JnHthgCgmq08tiXc9L78L5w7omyhaWJ3j/podY=; b=g05lVM71J7LWUPYzycIcbCYaUaCwtXo68VxZ+tEMhkqzJYBmDfGaKiPQlsucZ4Kcfc HzbNqn1RXQMWFbjgBEtOZ/g4tAcpN79WM3/ZpLDKSrvkBEbKjHiO46FNwa7YW2zT3Pft 7QdqoT/6atD4b4M0KkRNM7Eh5+mz+kZ8le7tSb0v7qniX/5j0zUckZwr2Us9vuOuoNC5 3XmQ9vnzrn9YO6WcwmZB/4K/6ineczpvlt9X/5Rs3VtZgmA4SnsjGpXdGesC5xNQSBIg c1TgByGVx8Hd4R0wO/9MLweKidlUTFz0iumoebZNATEyJ8CW7dYBUJBgsLBX4cSLD8hs R/Lw== X-Gm-Message-State: APjAAAXXJ3ImJZnylpVvPlgbbEIgevp2u2zrJXSe+hCA1t96igYDK2sR E8gU2ObtUMRpPHRTMXCq4G/cxw== X-Google-Smtp-Source: APXvYqzn6zuSHoGvZpYGa7hqC0hAik4W4vpY9vA8KctZspR1pc0UMWjB6L1RxysITXpB+qIoPK8kbw== X-Received: by 2002:a1c:39d7:: with SMTP id g206mr6721658wma.99.1554458870928; Fri, 05 Apr 2019 03:07:50 -0700 (PDT) Received: from steredhat (host35-203-static.12-87-b.business.telecomitalia.it. [87.12.203.35]) by smtp.gmail.com with ESMTPSA id n11sm32222748wrt.63.2019.04.05.03.07.49 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 05 Apr 2019 03:07:50 -0700 (PDT) Date: Fri, 5 Apr 2019 12:07:47 +0200 From: Stefano Garzarella To: Stefan Hajnoczi Cc: netdev@vger.kernel.org, Jason Wang , "Michael S. Tsirkin" , Stefan Hajnoczi , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, "David S. Miller" Subject: Re: [PATCH RFC 3/4] vsock/virtio: change the maximum packet size allowed Message-ID: <20190405100747.dbwi3sjaudp3d2wa@steredhat> References: <20190404105838.101559-1-sgarzare@redhat.com> <20190404105838.101559-4-sgarzare@redhat.com> <20190405082447.GD25152@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190405082447.GD25152@stefanha-x1.localdomain> User-Agent: NeoMutt/20180716 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Message-ID: <20190405100747.zNTOE-9HkrVBfd67It0rp8IkKt-rOY1kBSv0DtO--MQ@z> On Fri, Apr 05, 2019 at 09:24:47AM +0100, Stefan Hajnoczi wrote: > On Thu, Apr 04, 2019 at 12:58:37PM +0200, Stefano Garzarella wrote: > > Since now we are able to split packets, we can avoid limiting > > their sizes to VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE. > > Instead, we can use VIRTIO_VSOCK_MAX_PKT_BUF_SIZE as the max > > packet size. > > > > Signed-off-by: Stefano Garzarella > > --- > > net/vmw_vsock/virtio_transport_common.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > > index f32301d823f5..822e5d07a4ec 100644 > > --- a/net/vmw_vsock/virtio_transport_common.c > > +++ b/net/vmw_vsock/virtio_transport_common.c > > @@ -167,8 +167,8 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > > vvs = vsk->trans; > > > > /* we can send less than pkt_len bytes */ > > - if (pkt_len > VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE) > > - pkt_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE; > > + if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) > > + pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE; > > The next line limits pkt_len based on available credits: > > /* virtio_transport_get_credit might return less than pkt_len credit */ > pkt_len = virtio_transport_get_credit(vvs, pkt_len); > > I think drivers/vhost/vsock.c:vhost_transport_do_send_pkt() now works > correctly even with pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE. Correct. > > The other ->send_pkt() callback is > net/vmw_vsock/virtio_transport.c:virtio_transport_send_pkt_work() and it > can already send any size packet. > > Do you remember why VIRTIO_VSOCK_MAX_PKT_BUF_SIZE still needs to be the > limit? I'm wondering if we can get rid of it now and just limit packets > to the available credits. There are 2 reasons why I left this limit: 1. When the host receives a packets, it must be <= VIRTIO_VSOCK_MAX_PKT_BUF_SIZE [drivers/vhost/vsock.c:vhost_vsock_alloc_pkt()] So in this way we can limit the packets sent from the guest. 2. When the host send packets, it help us to increase the parallelism (especially if the guest has 64 KB RX buffers) because the user thread will split packets, calling multiple times transport->stream_enqueue() in net/vmw_vsock/af_vsock.c:vsock_stream_sendmsg() while the vhost_transport_send_pkt_work() send them to the guest. Do you think make sense? Thanks, Stefano