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Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] virtio: limit avail bytes lookahead |
Date: |
Wed, 28 Nov 2012 23:53:08 +0200 |
On Tue, Nov 27, 2012 at 06:25:04PM +0200, Michael S. Tsirkin wrote:
> 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?
virtio rng was added since so naturally build broke.
Here's a patch on top to fix it up. I never used virtio rng before so
could not test at this hour, but it does fix the build.
I'll take a look at how to test it tomorrow but any
info would be appreciated.
Amit could you pls review?
--
diff --git a/hw/virtio-rng.c b/hw/virtio-rng.c
index df329f2..a73ef8e 100644
--- a/hw/virtio-rng.c
+++ b/hw/virtio-rng.c
@@ -43,11 +43,11 @@ static bool is_guest_ready(VirtIORNG *vrng)
return false;
}
-static size_t get_request_size(VirtQueue *vq)
+static size_t get_request_size(VirtQueue *vq, unsigned quota)
{
unsigned int in, out;
- virtqueue_get_avail_bytes(vq, &in, &out);
+ virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
return in;
}
@@ -84,12 +84,18 @@ static void chr_read(void *opaque, const void *buf, size_t
size)
static void virtio_rng_process(VirtIORNG *vrng)
{
size_t size;
+ unsigned quota;
if (!is_guest_ready(vrng)) {
return;
}
- size = get_request_size(vrng->vq);
+ if (vrng->quota_remaining < 0) {
+ quota = 0;
+ } else {
+ quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
+ }
+ size = get_request_size(vrng->vq, quota);
size = MIN(vrng->quota_remaining, size);
if (size) {
rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
- Re: [Qemu-devel] [Bug 1066055] Re: Network performance regression with vde_switch, (continued)
- 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, 2012/11/27
- 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 <=
- 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