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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 13:12:18 +0300 |
On Mon, Sep 21, 2015 at 11:44:38PM +0200, Marc-André Lureau wrote:
> Hi
>
> On Mon, Sep 21, 2015 at 9:29 PM, Michael S. Tsirkin <address@hidden> wrote:
> >> Can this be considered a future enhancement?
> >
> > What's the big issue? Just count the devices that need a shared one, if
> > that count is 0 reallocate with shared == false.
>
>
> But then it should also VHOST_SET_LOG_BASE all the other devices with
> the new log, unless you want to tackle only the future log users. So
> it needs to track all the users of the log.
We already do this.
Same applies to non-memfd->memfd switch.
> 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.
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.
> --
> Marc-André Lureau
- [Qemu-devel] [PATCH v4 02/22] vhost-user: add protocol feature negotiation, (continued)
- [Qemu-devel] [PATCH v4 02/22] vhost-user: add protocol feature negotiation, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 03/22] vhost-user: unit test for new messages, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 04/22] configure: probe for memfd, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 05/22] util: add linux-only memfd fallback, marcandre . lureau, 2015/09/19
- [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 <=
- 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, 2015/09/22
[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