[lttng-dev] HugePages shared memory support in LLTng

[Jonathan Rajotte-Julien]

Hi Yiteng,

Make sure to always CC the mailing list.

> > Were you able to observe a positive impact?
> >
> > This is something we might be interested in upstreaming if we have good
> > feedback.
> 
> Yes, page faults disappeared and I didn't get those periodic overheads anymore.

Good. We will have to discuss this with Mathieu Desnoyers when he is back from
vacation and see if always using MAP_POPULATE make sense.

> 
> And I also solved the problem that hugepages are not closed correctly
> in my patch. It is my fault that I forgot to close the mmap pointer. I
> updated the patch here:
> https://github.com/lttng/lttng-ust/compare/master...guoyiteng:hugepages

Good. Would you be interested in posting those patches as RFC on the mailing
list so that we have a trace of this work in the future? Github cannot give us
the persistence needed for this. It might also lead to broader discussion.

> The current prefault solution works well for me and I will use that
> for now. In my opinion, using hugepages could further reduce the TLB
> misses, but that involved more changes in source codes than the
> prefault solution.
> 
> Best,
> Yiteng

-- 
Jonathan Rajotte-Julien
EfficiOS