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Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log |
Date: |
Tue, 22 Sep 2015 13:01:03 +0200 |
Hi
On Tue, Sep 22, 2015 at 12:12 PM, Michael S. Tsirkin <address@hidden> wrote:
>> 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.
>
I failed to see how the log of other devices is being updated when one
device needs a resize. There are multiple log already in this case.
>> 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?
> 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).
--
Marc-André Lureau
- [Qemu-devel] [PATCH v4 03/22] vhost-user: unit test for new messages, (continued)
- [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, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log,
Marc-André Lureau <=
- 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
[Qemu-devel] [PATCH v4 10/22] vhost-user: remove vhost_user_request_translate(), marcandre . lureau, 2015/09/19