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Re: [Xen-devel] [for-4.7] x86/emulate: synchronize LOCKed instruction emulation

>>> On 26.04.16 at 19:39, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 26/04/16 18:23, Razvan Cojocaru wrote:
>> Regarding this version of the patch, Jan has asked for more information
>> on the performance impact, but I'm not sure how to obtain it in a
>> rigorous manner. If it is decided that a version of this patch is
>> desirable, I can go on fixing the issues we've found and address the
>> comments we've had so far and submit a new version.
> XenServer did performance testing.  No observable impact for normal VM
> workloads (which is to be expected, as an OS wouldn't normally LOCK the
> instructions it uses for MMIO).  The per-cpu rwlocks have ~0 overhead
> when the lock isn't held for writing.

So how about PV guests doing locked page table updates, or the
impact on log-dirty mode?


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