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Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead
From: |
Edivaldo de Araujo Pereira |
Subject: |
Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead |
Date: |
Tue, 27 Nov 2012 08:54:26 -0800 (PST) |
Dear friends,
Please excuse-me for not reporting earlier... I confirm that the patch by
Michael really fixes the problem I've reported. The regression has gone away
when I used it, so I think it is good to be applied.
Thanks,
Edivaldo de Araújo Pereira
--- Em ter, 27/11/12, Michael S. Tsirkin <address@hidden> escreveu:
> De: Michael S. Tsirkin <address@hidden>
> Assunto: Re: [PATCH] virtio: limit avail bytes lookahead
> Para: "Amit Shah" <address@hidden>
> Cc: "Stefan Hajnoczi" <address@hidden>, "Edivaldo de Araujo Pereira"
> <address@hidden>, address@hidden, "Anthony Liguori" <address@hidden>, "Bug
> 1066055" <address@hidden>
> Data: Terça-feira, 27 de Novembro de 2012, 8:25
> On Thu, Nov 01, 2012 at 06:07:21PM
> +0200, Michael S. Tsirkin wrote:
> > Commit 0d8d7690850eb0cf2b2b60933cf47669a6b6f18f
> introduced
> > a regression in virtio-net performance because it
> looks
> > into the ring aggressively while we really only care
> > about a single packet worth of buffers.
> > To fix, add parameters limiting lookahead, and
> > use in virtqueue_avail_bytes.
> >
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > Reported-by: Edivaldo de Araujo Pereira <address@hidden>
>
> Ping.
> Anthony - going to apply this?
>
>
> > ---
> >
> > Edivaldo could you please confirm this fixes
> regression?
> >
> > diff --git a/hw/virtio-serial-bus.c
> b/hw/virtio-serial-bus.c
> > index d20bd8b..a761cdc 100644
> > --- a/hw/virtio-serial-bus.c
> > +++ b/hw/virtio-serial-bus.c
> > @@ -297,7 +297,7 @@ size_t
> virtio_serial_guest_ready(VirtIOSerialPort *port)
> > if (use_multiport(port->vser)
> && !port->guest_connected) {
> > return 0;
> > }
> > - virtqueue_get_avail_bytes(vq,
> &bytes, NULL);
> > + virtqueue_get_avail_bytes(vq,
> &bytes, NULL, UINT_MAX, 0);
> > return bytes;
> > }
> >
> > diff --git a/hw/virtio.c b/hw/virtio.c
> > index ec8b7d8..f40a8c5 100644
> > --- a/hw/virtio.c
> > +++ b/hw/virtio.c
> > @@ -336,7 +336,8 @@ static unsigned
> virtqueue_next_desc(hwaddr desc_pa,
> > }
> >
> > void virtqueue_get_avail_bytes(VirtQueue *vq,
> unsigned int *in_bytes,
> > -
>
> unsigned int *out_bytes)
> > +
>
> unsigned int *out_bytes,
> > +
>
> unsigned max_in_bytes, unsigned
> max_out_bytes)
> > {
> > unsigned int idx;
> > unsigned int total_bufs, in_total,
> out_total;
> > @@ -385,6 +386,9 @@ void
> virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int
> *in_bytes,
> > } else
> {
> >
> out_total += vring_desc_len(desc_pa, i);
> > }
> > + if (in_total
> >= max_in_bytes && out_total >= max_out_bytes)
> {
> > +
> goto done;
> > + }
> > } while ((i =
> virtqueue_next_desc(desc_pa, i, max)) != max);
> >
> > if (!indirect)
> > @@ -392,6 +396,7 @@ void
> virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int
> *in_bytes,
> > else
> >
> total_bufs++;
> > }
> > +done:
> > if (in_bytes) {
> > *in_bytes =
> in_total;
> > }
> > @@ -405,12 +410,8 @@ int
> virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,
> > {
> > unsigned int in_total, out_total;
> >
> > - virtqueue_get_avail_bytes(vq,
> &in_total, &out_total);
> > - if ((in_bytes && in_bytes <
> in_total)
> > - || (out_bytes &&
> out_bytes < out_total)) {
> > - return 1;
> > - }
> > - return 0;
> > + virtqueue_get_avail_bytes(vq,
> &in_total, &out_total, in_bytes, out_bytes);
> > + return in_bytes <= in_total
> && out_bytes <= out_total;
> > }
> >
> > void virtqueue_map_sg(struct iovec *sg, hwaddr
> *addr,
> > diff --git a/hw/virtio.h b/hw/virtio.h
> > index ac482be..1278328 100644
> > --- a/hw/virtio.h
> > +++ b/hw/virtio.h
> > @@ -150,7 +150,8 @@ int virtqueue_pop(VirtQueue *vq,
> VirtQueueElement *elem);
> > int virtqueue_avail_bytes(VirtQueue *vq, unsigned
> int in_bytes,
> >
> unsigned int
> out_bytes);
> > void virtqueue_get_avail_bytes(VirtQueue *vq,
> unsigned int *in_bytes,
> > -
>
> unsigned int *out_bytes);
> > +
>
> unsigned int *out_bytes,
> > +
>
> unsigned max_in_bytes, unsigned
> max_out_bytes);
> >
> > void virtio_notify(VirtIODevice *vdev, VirtQueue
> *vq);
> >
>
- Re: [Qemu-devel] [Bug 1066055] Re: Network performance regression with vde_switch, Amit Shah, 2012/11/01
- Re: [Qemu-devel] [Bug 1066055] Re: Network performance regression with vde_switch, Michael S. Tsirkin, 2012/11/01
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Michael S. Tsirkin, 2012/11/27
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead,
Edivaldo de Araujo Pereira <=
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Anthony Liguori, 2012/11/27
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Michael S. Tsirkin, 2012/11/28
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Amit Shah, 2012/11/29
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Michael S. Tsirkin, 2012/11/29
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Anthony Liguori, 2012/11/29
- Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead, Michael S. Tsirkin, 2012/11/29