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Re: [Qemu-devel] [PATCH v2 0/5] AArch64 TLB performance improvements
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [PATCH v2 0/5] AArch64 TLB performance improvements |
Date: |
Mon, 04 Aug 2014 12:34:22 +0100 |
Alex Bennée writes:
> Paolo Bonzini writes:
>
>> Il 30/07/2014 17:20, Alex Bennée ha scritto:
>>> Hi,
>>>
> <snip>
>>> The most important thing is I've measured a 25-30% improvement in
>>> kernel and android boot time.
>>>
> <snip>
>> Hi Alex, have you seen this patch? Perhaps you're interested in
>> reviving it.
>>
>> http://article.gmane.org/gmane.comp.emulators.qemu/253864
>
> I saw it when it first came out but I didn't quite follow what it was
> doing as I hadn't looked at the TLB code. I'll have another look and see
> what difference it can make.
A quick and dirty benchmark:
**** Comparing 10bit/12bit tables with and without
[[http://article.gmane.org/gmane.comp.emulators.qemu/253864][victim cache]]
#+BEGIN_NOTES
Time in seconds, smaller is better
Percentage is amount of time compared to run to the left
#+END_NOTES
| Code | 10 bit | 10 bit + victim | 12 bit | 12 bit + victim |
|-------+----------+-----------------+-----------+-----------------|
| | 12.783 | 11.664 | 10.348 | 9.527 |
| Runs | 13.046 | 11.971 | 10.123 | 9.326 |
| | 12.929 | 11.673 | 11.130 | 9.858 |
| | 12.981 | 11.941 | 10.223 | 9.673 |
|-------+----------+-----------------+-----------+-----------------|
| Avgs | 12.93475 | 11.81225 | 10.456 | 9.596 |
|-------+----------+-----------------+-----------+-----------------|
| %prev | 100% | 91.321827 | 88.518276 | 91.775057 |
#+TBLFM:
$2=vmean(@I..II)::$3=(@II$3/@II$2)*100::$4=vmean(@I..II)::$5=vmean(@I..II)
Which as you expect shows the page table size is a greater improvement
to the performance but the victim cache also improves the run time on
top of this.
I say as you would expect because any time you need to exit translated
code there is a bunch of overhead in doing so.
--
Alex Bennée