Patch series implementing speculative page faults for x86.
Still needs lots of things sorted, like:
- call_srcu()
- ptl, irq and tlb-flush
- a 2nd VM_FAULT_LOCK? return code to distuinguish between
simple retry and must take mmap_sem semantics?
Comments?
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On 01/04/2010 01:24 PM, Peter Zijlstra wrote:
> Patch series implementing speculative page faults for x86.
Fun, but why do we need this?
What improvements did you measure?
I'll take a look over the patches to see whether they're
sane...
--
All rights reversed.
On Mon, 2010-01-04 at 16:41 -0500, Rik van Riel wrote:
> On 01/04/2010 01:24 PM, Peter Zijlstra wrote:
> > Patch series implementing speculative page faults for x86.
>
> Fun, but why do we need this?
People were once again concerned with mmap_sem contention on threaded
apps on large machines. Kame-san posted some patches, but I felt they
weren't quite crazy enough ;-)
> What improvements did you measure?
I got it not to crash :-) Although I'd not be surprised if other people
do manage, it needs more eyes.
> I'll take a look over the patches to see whether they're
> sane...
More appreciated, thanks!
On Mon, 4 Jan 2010, Rik van Riel wrote:
> Fun, but why do we need this?
>
> What improvements did you measure?
If it measures up to Kame-sans approach then the possible pagefault rate
will at least double ...
On 01/04/2010 04:46 PM, Peter Zijlstra wrote:
> On Mon, 2010-01-04 at 16:41 -0500, Rik van Riel wrote:
>> On 01/04/2010 01:24 PM, Peter Zijlstra wrote:
>>> Patch series implementing speculative page faults for x86.
>>
>> Fun, but why do we need this?
>
> People were once again concerned with mmap_sem contention on threaded
> apps on large machines. Kame-san posted some patches, but I felt they
> weren't quite crazy enough ;-)
In that case, I assume that somebody else (maybe Kame-san or
Christoph) will end up posting a benchmark that shows how
these patches help.
--
All rights reversed.
On Mon, 4 Jan 2010 15:59:45 -0600 (CST)
Christoph Lameter <[email protected]> wrote:
> On Mon, 4 Jan 2010, Rik van Riel wrote:
>
> > Fun, but why do we need this?
> >
> > What improvements did you measure?
>
> If it measures up to Kame-sans approach then the possible pagefault rate
> will at least double ...
>
On 4-core/2 socket machine ;)
More than page fault rate, important fact is that we can reduce cache contention
by skipping mmap_sem in some situation.
And I think we have some chances.
Thanks,
-Kame
Hi, Peter.
On Tue, Jan 5, 2010 at 3:24 AM, Peter Zijlstra <[email protected]> wrote:
> Patch series implementing speculative page faults for x86.
>
> Still needs lots of things sorted, like:
>
> - call_srcu()
> - ptl, irq and tlb-flush
> - a 2nd VM_FAULT_LOCK? return code to distuinguish between
> simple retry and must take mmap_sem semantics?
>
> Comments?
> --
>
>
I looked over this patch series.
This series are most neat in things I have ever seen.
If we solve call_srcu problem, it would be good.
I will help you test this series in my machine to work well.
--
Kind regards,
Minchan Kim