[lttng-dev] HugePages shared memory support in LLTng

[Jonathan Rajotte-Julien]

hi Yiteng,

On Mon, Jul 22, 2019 at 03:23:08PM -0400, Jonathan Rajotte-Julien wrote:
> Hi Yiteng,
> 
> On Mon, Jul 22, 2019 at 02:44:09PM -0400, Yiteng Guo wrote:
> > Hi Jonathan,
> > 
> > I spent these days on this problem and finally figured it out. Here
> > are patches I've written.
> 
> Sorry for that, I had other stuff ongoing.
> 
> I had a brief discussion about this with Mathieu Desnoyers.
> 
> Mathieu mentioned that the page faults you are seeing might be related to
> qemu/kvm usage of KSM [1]. I did not have time to play around with it and see if
> this indeed have an effect. You might be better off trying it since you are
> already all setup. Might want to disable it and retry your experiment (if only
> doing this on a vm).

Disregard all of this for now. I think we misunderstood the first email and got
too far too fast.

I modified lttng-ust to use MAP_POPULATE and based on the result from the page_fault
perf counter it seems to achieve what you are looking for.

See attached patch. Let me know if this help.

Cheers.
-- 
Jonathan Rajotte-Julien
EfficiOS
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