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Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user |
Date: |
Fri, 28 Oct 2016 01:11:51 +0300 |
On Tue, Oct 18, 2016 at 04:21:57PM +0000, Felipe Franciosi wrote:
>
> > On 18 Oct 2016, at 16:25, Marc-André Lureau <address@hidden> wrote:
> >
> > Hi Felipe
> >
> > ----- Original Message -----
> >> Hello,
> >>
> >>> On 18 Oct 2016, at 10:24, Marc-André Lureau <address@hidden>
> >>> wrote:
> >>>
> >>> <...>
> >>>
> >>> diff --git a/contrib/libvhost-user/libvhost-user.h
> >>> b/contrib/libvhost-user/libvhost-user.h
> >>>
> >>> <...>
> >>>
> >>> +#define VHOST_MAX_NR_VIRTQUEUE 8
> >>> +#define VIRTQUEUE_MAX_SIZE 1024
> >>
> >> I think that the maximum number of VQs should be 1024 to match Qemu's.
> >>
> >> http://git.qemu.org/?p=qemu.git;a=blob;f=include/hw/virtio/virtio.h;h=b913aac45589449bcc5d8161651332f4b0d69c7f;hb=HEAD#l55
> >
> > That would make the VuDev structure quite big. We may want to set the nr of
> > max queues in vu_init() instead, and allocate it there. I think this is
> > rather a current limitation, but does not prevent iterating from there.
>
> Well, it depends what we call "quite big". The only thing that depends on
> that is:
>
> > struct VuDev {
> > <...>
> > VuVirtq vq[VHOST_MAX_NR_VIRTQUEUE];
> > <...>
>
> And VuVirtq is 96 bytes in size (x86_64). So we're really talking about 768
> bytes vs 96 KiB.
>
> Actually, you can bring it down to 88 bytes by...
>
> > typedef struct VuRing {
> > unsigned int num;
> > struct vring_desc *desc;
> > struct vring_avail *avail;
> > struct vring_used *used;
> > uint64_t log_guest_addr;
> > uint32_t flags;
>
> ... moving "flags" just below "num". Allows gcc to compact the struct better.
>
> > } VuRing;
>
>
> I'd rather fix this kind of thing sooner than later, but it's ultimately up
> to you.
>
> Felipe
I suspect the right thing to do is allocating it dynamically,
I'm fine merging as is for now though.
--
MST
- [Qemu-devel] [PATCH v2 0/6] Start a contrib/libvhost-user, (continued)
- [Qemu-devel] [PATCH v2 0/6] Start a contrib/libvhost-user, Marc-André Lureau, 2016/10/18
- [Qemu-devel] [PATCH v2 1/6] tests/vhost-user-bridge: remove false comment, Marc-André Lureau, 2016/10/18
- [Qemu-devel] [PATCH v2 2/6] tests/vhost-user-bridge: remove unnecessary dispatcher_remove, Marc-André Lureau, 2016/10/18
- [Qemu-devel] [PATCH v2 3/6] tests/vhost-user-bridge: indicate peer disconnected, Marc-André Lureau, 2016/10/18
- [Qemu-devel] [PATCH v2 4/6] tests/vhost-user-bridge: do not accept more than one connection, Marc-André Lureau, 2016/10/18
- [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user, Marc-André Lureau, 2016/10/18
- Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user, Felipe Franciosi, 2016/10/18
- Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user, Felipe Franciosi, 2016/10/18
- Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user, Marc-André Lureau, 2016/10/18
- Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user, Felipe Franciosi, 2016/10/18
- Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH v2 5/6] contrib: add libvhost-user, Felipe Franciosi, 2016/10/27
[Qemu-devel] [PATCH v2 6/6] tests/vhost-user-bridge: use contrib/libvhost-user, Marc-André Lureau, 2016/10/18