Re: VM memory allocation speed with cs 26056

[Zhigang Wang <zhigang.x.wang@oracle.com>]

[-- Attachment #1: Type: text/plain, Size: 1880 bytes --]

On 11/13/2012 10:46 AM, Zhigang Wang wrote:
> On 11/12/2012 01:25 PM, Keir Fraser wrote:
>> On 12/11/2012 15:01, "Zhigang Wang" <zhigang.x.wang@oracle.com> wrote:
>>
>>> Hi Keir/Jan,
>>>
>>> Recently I got a chance to access a big machine (2T mem/160 cpus) and I tested
>>> your patch: http://xenbits.xen.org/hg/xen-unstable.hg/rev/177fdda0be56
>>>
>>> Attached is the result.
>> The PVM result is weird, there is a small-ish slowdown for small domains,
>> becoming a very large %age slowdown as domain memory increases, and then
>> turning into a *speedup* as the memory size gets very large indeed.
>>
>> What are the error bars like on these measurements I wonder? One thing we
>> could do to allow PV guests doing 4k-at-a-time allocations through
>> alloc_heap_pages() to benefit from the TLB-flush improvements, is pull the
>> filtering-and-flush out into populate_physmap() and increase_reservation().
>> This is listed as a todo in the original patch (26056).
>>
>> To be honest I don't know why the original patch would make PV domain
>> creation slower, and certainly not by a varying %age depending on domain
>> memory size!
>>
>>  -- Keir
> I did it second time. It seems the result (attached) is promising.
>
> I think the strange result is due to the order of testing:
> start_physical_machine -> test_hvm -> test_pvm.
>
> This time, I did: start_physical_machine -> test_pvm -> test_hvm.
>
> You can see the pvm memory allocation speed is not affected by your patch this time.
>
> So I believe this patch is excellent now.

I get another chance to run the test without (old) and with (new) cs 25056 with
order:

start_physical_machine -> test_hvm -> test_pvm

It seems PV guest memory allocation is not affected by this patch, although it
makes a big difference if testing with order:

start_physical_machine -> test_pvm -> test_hvm

Thanks for the patch.

Zhigang


[-- Attachment #2: result.pdf --]
[-- Type: application/pdf, Size: 15769 bytes --]

[-- Attachment #3: Type: text/plain, Size: 126 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel