netdev - Re: [PATCH 2/2] virtio_net: remove send completion interrupts and avoid TX queue overrun through packet drop

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1300375115.3255.45.camel@localhost.localdomain>
Date:	Thu, 17 Mar 2011 08:18:35 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	David Miller <davem@...emloft.net>, kvm@...r.kernel.org,
	netdev@...r.kernel.org, Herbert Xu <herbert@...dor.hengli.com.au>
Subject: Re: [PATCH 2/2] virtio_net: remove send completion interrupts and
 avoid TX queue overrun through packet drop

On Thu, 2011-03-17 at 07:02 +0200, Michael S. Tsirkin wrote:
> So, this just tries to make sure there's enough space for
> max packet in the ring, if not - drop and return OK.
> Why bother checking beforehand though?
> If that's what we want to do, we can just call add_buf and see
> if it fails?

In add_buf, there is an additional kick, see below. I added check
capacity to avoid this, thought it would be better performance. I will
retest it w/i add_buf to see the performance difference.

        if (vq->num_free < out + in) {
                pr_debug("Can't add buf len %i - avail = %i\n",
                         out + in, vq->num_free);
                /* FIXME: for historical reasons, we force a notify here
if
                 * there are outgoing parts to the buffer.  Presumably
the
                 * host should service the ring ASAP. */
                if (out)
                        vq->notify(&vq->vq);
                END_USE(vq);
                return -ENOSPC;
        }

Thanks
Shirley

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html