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Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log |
Date: |
Tue, 22 Sep 2015 14:54:21 +0300 |
On Tue, Sep 22, 2015 at 01:50:47PM +0200, Marc-André Lureau wrote:
> hi
>
> On Tue, Sep 22, 2015 at 1:41 PM, Michael S. Tsirkin <address@hidden> wrote:
> > There's a single log at the moment:
> > static struct vhost_log *vhost_log;
> >
> > But all devices are updated by the memory core, we don't
> > have a list in the vhost code.
>
> Do you mean that all devices will have their memory listener restart
> the log, so they all point to the same global vhost_log?
Exactly.
> >> >> Is there a clear benefit
> >> >> of this? since the memory isn't shared without the memfd passed to
> >> >> another process and the overhead of memfd is probably quite small, and
> >> >> pre-shm or future resize will not use the shared memory already.
> >> >
> >> > For example, THP doesn't work for memfd at the moment,
> >> > so all accesses are a bit slower.
> >>
> >> What's THP? How is it slower once the fd is mmap?
> >
> > Transparent huge page. This process doesn't work for
> > memfd AFAIK.
> >
> >> > Really, I don't want to merge hacks. Switching from non memfd
> >> > to memfd but not back has all the signs of one.
> >> > Let's do it cleanly please.
> >>
> >> The current code isn't switching existing logs either. What would be
> >> simpler to do is to allocate a different log region for the "share"
> >> case. So there would be no need to switch other non-shareable logs (to
> >> the cost of using twice the memory needed).
> >
> > OK, that's not too bad. Let's go for it.
>
>
> ok, working on new patch
I've tentatively applied the multiqueue patches, please make sure
yours work on top.
> --
> Marc-André Lureau
- [Qemu-devel] [PATCH v4 06/22] util: add memfd helpers, (continued)
- [Qemu-devel] [PATCH v4 06/22] util: add memfd helpers, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, marcandre . lureau, 2015/09/19
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log,
Michael S. Tsirkin <=
[Qemu-devel] [PATCH v4 08/22] vhost: document log resizing, marcandre . lureau, 2015/09/19
[Qemu-devel] [PATCH v4 09/22] vhost: use a function for each call, marcandre . lureau, 2015/09/19
[Qemu-devel] [PATCH v4 10/22] vhost-user: remove vhost_user_request_translate(), marcandre . lureau, 2015/09/19
[Qemu-devel] [PATCH v4 11/22] vhost-user: send log shm fd along with log_base, marcandre . lureau, 2015/09/19