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Re: [Xen-devel] [for-4.7] x86/emulate: synchronize LOCKed instruction emulation
- To: "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx>
- From: "Jan Beulich" <JBeulich@xxxxxxxx>
- Date: Wed, 27 Apr 2016 00:25:07 -0600
- Cc: wei.liu2@xxxxxxxxxx, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>, george.dunlap@xxxxxxxxxxxxx, tim@xxxxxxx, ian.jackson@xxxxxxxxxxxxx, George Dunlap <george.dunlap@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxx, paul.durrant@xxxxxxxxxx, david.vrabel@xxxxxxxxxx, keir@xxxxxxx
- Delivery-date: Wed, 27 Apr 2016 06:25:13 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
>>> 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?
Jan
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