[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory.
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory. |
Date: |
Wed, 18 Jul 2012 11:32:55 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
On 07/17/2012 09:36 PM, Stefano Stabellini wrote:
> On Tue, 17 Jul 2012, Avi Kivity wrote:
>> On 07/17/2012 04:59 PM, Anthony PERARD wrote:
>> >>
>> >> This is pretty ugly. An alternative is to set up a periodic bitmap scan
>> >> that looks at the qemu dirty bitmap and calls xen_modified_memory() for
>> >> dirty page ranges, and clears the bitmap for the next pass. Is it
>> >> workable?
>> >
>> > I don't think a periodic scan can do anything useful, unfortunately.
>>
>> Why not?
>
> I vaguely remember that we used to have a bitmap years ago, but, aside from
> making the code much more complicated, it caused blue screens on
> intensive disk accesses.
Surely it was some bug, not the scan itself.
>
>
>> >> (is xen_modified_memory a hypercall, or does it maintain an in-memory
>> >> structure?)
>> >
>> > It's an hypercall. The function do something (call the hypercall) only
>> > during migration, otherwise it return immediately.
>>
>> I see. I guess it isn't expensive for you because there isn't much dma
>> done by qemu usually with xen (unlike kvm where pv block devices are
>> implemented in qemu).
>>
>> How about pushing the call into cpu_physical_memory_set_dirty_flags()?
>> Would that reduce the number of call sites?
>
> Pushing the calls to cpu_physical_memory_set_dirty_flags and
> cpu_physical_memory_set_dirty_range would make the code much nicer.
> However being these functions in exec-obsolete.h, are they at risk of
> removal?
exec-obsolete.h just means don't add new call sites. The functions
won't be removed, instead they'll be absorbed into the memory code with
different names and different implementations.
--
error compiling committee.c: too many arguments to function
- [Qemu-devel] [PATCH 0/4] Xen, introducing dirty log for migration., Anthony PERARD, 2012/07/17
- [Qemu-devel] [PATCH 2/4] xen: Introduce xen_modified_memory., Anthony PERARD, 2012/07/17
- [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Anthony PERARD, 2012/07/17
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Avi Kivity, 2012/07/17
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Anthony PERARD, 2012/07/17
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Avi Kivity, 2012/07/17
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Stefano Stabellini, 2012/07/17
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory.,
Avi Kivity <=
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Anthony PERARD, 2012/07/19
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Avi Kivity, 2012/07/19
- Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Anthony PERARD, 2012/07/19
Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory., Stefano Stabellini, 2012/07/17
[Qemu-devel] [PATCH 1/4] QMP, Introduce set-global-dirty-log command., Anthony PERARD, 2012/07/17