From: "Michael S. Tsirkin" <mst@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Stefan Hajnoczi <stefanha@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
virtualization@lists.linux-foundation.org,
Jason Wang <jasowang@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH v4 1/5] vsock/virtio: limit the memory used per-socket
Date: Mon, 29 Jul 2019 12:01:37 -0400 [thread overview]
Message-ID: <20190729115904-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20190729153656.zk4q4rob5oi6iq7l@steredhat>
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 <stefanha@redhat.com>
> > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> >
> > 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.
>
> Thanks,
> Stefano
next prev parent reply other threads:[~2019-07-29 16:01 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 11:30 [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput Stefano Garzarella
2019-07-17 11:30 ` [PATCH v4 1/5] vsock/virtio: limit the memory used per-socket Stefano Garzarella
2019-07-29 14:04 ` Michael S. Tsirkin
2019-07-29 15:36 ` Stefano Garzarella
2019-07-29 15:49 ` Michael S. Tsirkin
2019-07-29 16:19 ` Stefano Garzarella
2019-07-29 16:50 ` Stefano Garzarella
2019-07-29 19:10 ` Michael S. Tsirkin
2019-07-30 9:35 ` Stefano Garzarella
2019-07-30 20:42 ` Michael S. Tsirkin
2019-08-01 10:47 ` Stefano Garzarella
2019-08-01 13:21 ` Michael S. Tsirkin
2019-08-01 13:36 ` Stefano Garzarella
2019-09-01 8:26 ` Michael S. Tsirkin
2019-09-01 10:17 ` Michael S. Tsirkin
2019-09-02 9:57 ` Stefano Garzarella
2019-09-02 15:23 ` Michael S. Tsirkin
2019-09-03 4:39 ` Michael S. Tsirkin
2019-09-03 7:45 ` Stefano Garzarella
2019-09-03 7:52 ` Michael S. Tsirkin
2019-09-03 8:00 ` Stefano Garzarella
2019-07-29 16:01 ` Michael S. Tsirkin [this message]
2019-07-29 16:41 ` Stefano Garzarella
2019-07-29 19:33 ` Michael S. Tsirkin
2019-08-30 9:40 ` Stefano Garzarella
2019-09-01 6:56 ` Michael S. Tsirkin
2019-09-02 8:39 ` Stefan Hajnoczi
2019-09-02 8:55 ` Stefano Garzarella
2019-10-11 13:40 ` Stefano Garzarella
2019-10-11 14:11 ` Michael S. Tsirkin
2019-10-11 14:23 ` Stefano Garzarella
2019-10-14 8:17 ` Stefan Hajnoczi
2019-10-14 8:21 ` Jason Wang
2019-10-14 8:38 ` Stefano Garzarella
2019-07-17 11:30 ` [PATCH v4 2/5] vsock/virtio: reduce credit update messages Stefano Garzarella
2019-07-22 8:36 ` Stefan Hajnoczi
2019-09-03 4:38 ` Michael S. Tsirkin
2019-09-03 7:31 ` Stefano Garzarella
2019-09-03 7:38 ` Michael S. Tsirkin
2019-07-17 11:30 ` [PATCH v4 3/5] vsock/virtio: fix locking in virtio_transport_inc_tx_pkt() Stefano Garzarella
2019-07-17 14:51 ` Michael S. Tsirkin
2019-07-18 7:43 ` Stefano Garzarella
2019-07-22 8:53 ` Stefan Hajnoczi
2019-07-17 11:30 ` [PATCH v4 4/5] vhost/vsock: split packets to send using multiple buffers Stefano Garzarella
2019-07-17 14:54 ` Michael S. Tsirkin
2019-07-18 7:50 ` Stefano Garzarella
2019-07-18 8:13 ` Michael S. Tsirkin
2019-07-18 9:37 ` Stefano Garzarella
2019-07-18 11:35 ` Michael S. Tsirkin
2019-07-19 8:08 ` Stefano Garzarella
2019-07-19 8:21 ` Jason Wang
2019-07-19 8:39 ` Stefano Garzarella
2019-07-19 8:51 ` Jason Wang
2019-07-19 9:20 ` Stefano Garzarella
2019-07-22 9:06 ` Stefan Hajnoczi
2019-07-17 11:30 ` [PATCH v4 5/5] vsock/virtio: change the maximum packet size allowed Stefano Garzarella
2019-07-17 14:59 ` Michael S. Tsirkin
2019-07-18 7:52 ` Stefano Garzarella
2019-07-18 12:33 ` Michael S. Tsirkin
2019-07-19 8:29 ` Stefano Garzarella
2019-07-22 9:07 ` Stefan Hajnoczi
2019-07-22 9:08 ` [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput Stefan Hajnoczi
2019-07-22 9:14 ` Stefano Garzarella
2019-07-29 13:12 ` Stefan Hajnoczi
2019-07-29 13:59 ` Michael S. Tsirkin
2019-07-30 9:40 ` Stefano Garzarella
2019-07-30 10:03 ` Jason Wang
2019-07-30 15:38 ` Stefano Garzarella
2019-09-03 8:02 ` request for stable (was Re: [PATCH v4 0/5] vsock/virtio: optimizations to increase the throughput) Michael S. Tsirkin
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