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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 84BA1C433FF for ; Mon, 29 Jul 2019 16:41:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64C66206A2 for ; Mon, 29 Jul 2019 16:41:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727924AbfG2Qlk (ORCPT ); Mon, 29 Jul 2019 12:41:40 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:36672 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726714AbfG2Qlj (ORCPT ); Mon, 29 Jul 2019 12:41:39 -0400 Received: by mail-oi1-f193.google.com with SMTP id q4so16564730oij.3 for ; Mon, 29 Jul 2019 09:41:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=qEnidYZvMtI0djmi8U0ZEWcmJ8XfKi49GrC/Gx0OghM=; b=iJR7OYOjRzHWCCc8hOGH9yDLDqur7PrWF3ZEKmrW+3hmOJMJ12aA8kZO1bQlJUX/03 RKi5vUgMtqT6dpX8biC2UN2b/XyLL9IfYwaeHjYIrIqEXzyLljQrRG435gZ/4hwHbSPl shyRur4wVIRwWOrw+faP6rDbKVv1c1Elt5vcb52VMsLXXsMoE2cb+Qn1KD+UfWj4vVyb RW0i3Uk5K2hgeG41swH88ZrrJCzCWwgxmuFHgw9EYE7qRBf88Be6lUmQDgOFPD84E1h+ 4KwRGB6Aal0lA5ComJblcDqV6C/iE9bvePu1FGpnD9Lu56m2RTll1Pz2g6qAx+wBiyAB IOyA== X-Gm-Message-State: APjAAAXRCw/WgrW+P5X2FoLtwblpBd3+wuEXnVQMSv6j0929zA8g/38u vkeNICl5KziVOcnDuQKUbWRBU4GR8poCxu3bWJnr1A== X-Google-Smtp-Source: APXvYqwLmyK1E/4jrfGUT98xeH//0WmrilX5ZcE9+u6f94aZr6eu7bn4vAgIsx2aZWLhabtNB/WLd0Vdna3tzy2IXKU= X-Received: by 2002:aca:1803:: with SMTP id h3mr20756041oih.24.1564418498709; Mon, 29 Jul 2019 09:41:38 -0700 (PDT) MIME-Version: 1.0 References: <20190717113030.163499-1-sgarzare@redhat.com> <20190717113030.163499-2-sgarzare@redhat.com> <20190729095956-mutt-send-email-mst@kernel.org> <20190729153656.zk4q4rob5oi6iq7l@steredhat> <20190729115904-mutt-send-email-mst@kernel.org> In-Reply-To: <20190729115904-mutt-send-email-mst@kernel.org> From: Stefano Garzarella Date: Mon, 29 Jul 2019 18:41:27 +0200 Message-ID: Subject: Re: [PATCH v4 1/5] vsock/virtio: limit the memory used per-socket To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Hajnoczi , "David S. Miller" , virtualization@lists.linux-foundation.org, Jason Wang , kvm@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jul 29, 2019 at 12:01:37PM -0400, Michael S. Tsirkin wrote: > On Mon, Jul 29, 2019 at 05:36:56PM +0200, Stefano Garzarella wrote: > > On Mon, Jul 29, 2019 at 10:04:29AM -0400, Michael S. Tsirkin wrote: > > > On Wed, Jul 17, 2019 at 01:30:26PM +0200, Stefano Garzarella wrote: > > > > Since virtio-vsock was introduced, the buffers filled by the host > > > > and pushed to the guest using the vring, are directly queued in > > > > a per-socket list. These buffers are preallocated by the guest > > > > with a fixed size (4 KB). > > > > > > > > The maximum amount of memory used by each socket should be > > > > controlled by the credit mechanism. > > > > The default credit available per-socket is 256 KB, but if we use > > > > only 1 byte per packet, the guest can queue up to 262144 of 4 KB > > > > buffers, using up to 1 GB of memory per-socket. In addition, the > > > > guest will continue to fill the vring with new 4 KB free buffers > > > > to avoid starvation of other sockets. > > > > > > > > This patch mitigates this issue copying the payload of small > > > > packets (< 128 bytes) into the buffer of last packet queued, in > > > > order to avoid wasting memory. > > > > > > > > Reviewed-by: Stefan Hajnoczi > > > > Signed-off-by: Stefano Garzarella > > > > > > This is good enough for net-next, but for net I think we > > > should figure out how to address the issue completely. > > > Can we make the accounting precise? What happens to > > > performance if we do? > > > > > > > In order to do more precise accounting maybe we can use the buffer size, > > instead of payload size when we update the credit available. > > In this way, the credit available for each socket will reflect the memory > > actually used. > > > > I should check better, because I'm not sure what happen if the peer sees > > 1KB of space available, then it sends 1KB of payload (using a 4KB > > buffer). > > The other option is to copy each packet in a new buffer like I did in > > the v2 [2], but this forces us to make a copy for each packet that does > > not fill the entire buffer, perhaps too expensive. > > > > [2] https://patchwork.kernel.org/patch/10938741/ > > > > So one thing we can easily do is to under-report the > available credit. E.g. if we copy up to 256bytes, > then report just 256bytes for every buffer in the queue. > Ehm sorry, I got lost :( Can you explain better? Thanks, Stefano