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=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 F40C6C04E53 for ; Wed, 15 May 2019 08:22:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEAED20843 for ; Wed, 15 May 2019 08:22:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726528AbfEOIWk (ORCPT ); Wed, 15 May 2019 04:22:40 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:38443 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725933AbfEOIWk (ORCPT ); Wed, 15 May 2019 04:22:40 -0400 Received: by mail-wm1-f65.google.com with SMTP id f2so1523382wmj.3 for ; Wed, 15 May 2019 01:22:38 -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:user-agent; bh=PPQSJiwlVW1PE92NeJWVh3dDEhwcNImDy2Q5NEYn4yo=; b=VazcWsFiKyvULxq1MEK6mjDwpYc0j0RCm9lw+vPvzc6beGqHwBsZO4zDq3ySghD23I lh5DLXTerHAXXlYsxaHiKTSXwh+VUxldx+dTDinEkuC1xOHUj9sUKWsh2OSKtJVmiRJ+ J2XM0enjF8tDYJHnUySAjyY3BdzYzyp70ZYWSwgkM8EsHY/K4V9xGy8piCWjKheaXHlk +hIwshN9wWjEbGdORDkOzDYkEkK2Sr3jSFKvC32Dz9mZKEvBiO4vXHIC9q6lpmamHIIN Z2BlM8g/G1jpSgKlqm6RgXkPntXqynX9dLADqWIs13XpuMMKZBXiJboIhEctfeDio3Ki P2rA== X-Gm-Message-State: APjAAAW53o9mlOpTvOSOHdzlcWEvUOoSpI528yxBclFjDe5mLWbymyot XdI+xK6v5hA0I0S0BB+NRpCzSw== X-Google-Smtp-Source: APXvYqwpXrWkAROlq0ytsK33r1VNVYl9awseeDiyNlDpFhZC69GGaWDX1zimAMr2LLpZz2MeWmJqQg== X-Received: by 2002:a1c:2104:: with SMTP id h4mr21953640wmh.146.1557908557541; Wed, 15 May 2019 01:22:37 -0700 (PDT) Received: from steredhat (host151-251-static.12-87-b.business.telecomitalia.it. [87.12.251.151]) by smtp.gmail.com with ESMTPSA id y184sm1579251wmg.7.2019.05.15.01.22.35 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 15 May 2019 01:22:36 -0700 (PDT) Date: Wed, 15 May 2019 10:22:33 +0200 From: Stefano Garzarella To: Jason Wang Cc: netdev@vger.kernel.org, "David S. Miller" , "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Stefan Hajnoczi Subject: Re: [PATCH v2 7/8] vsock/virtio: increase RX buffer size to 64 KiB Message-ID: <20190515082233.iqaibtfdoblijb5z@steredhat> References: <20190510125843.95587-1-sgarzare@redhat.com> <20190510125843.95587-8-sgarzare@redhat.com> <20190513175138.4yycad2xi65komw6@steredhat> <20190514162056.5aotcuzsi6e6wya7@steredhat> <646275c5-3530-f428-98da-56da99d72fe1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <646275c5-3530-f428-98da-56da99d72fe1@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 15, 2019 at 10:50:43AM +0800, Jason Wang wrote: > > On 2019/5/15 上午12:20, Stefano Garzarella wrote: > > On Tue, May 14, 2019 at 11:38:05AM +0800, Jason Wang wrote: > > > On 2019/5/14 上午1:51, Stefano Garzarella wrote: > > > > On Mon, May 13, 2019 at 06:01:52PM +0800, Jason Wang wrote: > > > > > On 2019/5/10 下午8:58, Stefano Garzarella wrote: > > > > > > In order to increase host -> guest throughput with large packets, > > > > > > we can use 64 KiB RX buffers. > > > > > > > > > > > > Signed-off-by: Stefano Garzarella > > > > > > --- > > > > > > include/linux/virtio_vsock.h | 2 +- > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h > > > > > > index 84b72026d327..5a9d25be72df 100644 > > > > > > --- a/include/linux/virtio_vsock.h > > > > > > +++ b/include/linux/virtio_vsock.h > > > > > > @@ -10,7 +10,7 @@ > > > > > > #define VIRTIO_VSOCK_DEFAULT_MIN_BUF_SIZE 128 > > > > > > #define VIRTIO_VSOCK_DEFAULT_BUF_SIZE (1024 * 256) > > > > > > #define VIRTIO_VSOCK_DEFAULT_MAX_BUF_SIZE (1024 * 256) > > > > > > -#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 4) > > > > > > +#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 64) > > > > > > #define VIRTIO_VSOCK_MAX_BUF_SIZE 0xFFFFFFFFUL > > > > > > #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE (1024 * 64) > > > > > We probably don't want such high order allocation. It's better to switch to > > > > > use order 0 pages in this case. See add_recvbuf_big() for virtio-net. If we > > > > > get datapath unified, we will get more stuffs set. > > > > IIUC, you are suggesting to allocate only pages and put them in a > > > > scatterlist, then add them to the virtqueue. > > > > > > > > Is it correct? > > > > > > Yes since you are using: > > > > > >                 pkt->buf = kmalloc(buf_len, GFP_KERNEL); > > >                 if (!pkt->buf) { > > >                         virtio_transport_free_pkt(pkt); > > >                         break; > > >                 } > > > > > > This is likely to fail when the memory is fragmented which is kind of > > > fragile. > > > > > > > > Thanks for pointing that out. > > > > > > The issue that I have here, is that the virtio-vsock guest driver, see > > > > virtio_vsock_rx_fill(), allocates a struct virtio_vsock_pkt that > > > > contains the room for the header, then allocates the buffer for the payload. > > > > At this point it fills the scatterlist with the &virtio_vsock_pkt.hdr and the > > > > buffer for the payload. > > > > > > This part should be fine since what is needed is just adding more pages to > > > sg[] and call virtuqeueu_add_sg(). > > > > > > > > Yes, I agree. > > > > > > Changing this will require several modifications, and if we get datapath > > > > unified, I'm not sure it's worth it. > > > > Of course, if we leave the datapaths separated, I'd like to do that later. > > > > > > > > What do you think? > > > > > > For the driver it self, it should not be hard. But I think you mean the > > > issue of e.g virtio_vsock_pkt itself which doesn't support sg. For short > > > time, maybe we can use kvec instead. > > I'll try to use kvec in the virtio_vsock_pkt. > > > > Since this struct is shared also with the host driver (vhost-vsock), > > I hope the changes could be limited, otherwise we can remove the last 2 > > patches of the series for now, leaving the RX buffer size to 4KB. > > > Yes and if it introduces too much changes, maybe we can do the 64KB buffer > in the future with the conversion of using skb where supports page frag > natively. Yes, I completely agree! Thanks, Stefano