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SubjectRe: [PATCH] Poll : introduce poll_wait_exclusive() new function
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> > Mathieu Desnoyers explained it cause following problem to LTTng.
> >
> > In LTTng, all lttd readers are polling all the available debugfs files
> > for data. This is principally because the number of reader threads is
> > user-defined and there are typical workloads where a single CPU is
> > producing most of the tracing data and all other CPUs are idle,
> > available to consume data. It therefore makes sense not to tie those
> > threads to specific buffers. However, when the number of threads grows,
> > we face a "thundering herd" problem where many threads can be woken up
> > and put back to sleep, leaving only a single thread doing useful work.
>
> Why do you need to have so many threads banging a single device/file?
> Have one (or any other very little number) puller thread(s), that
> activates with chucks of pulled data the other processing threads. That
> way there's no need for a new wakeup abstraction.

Mathieu, I don't hope I unstrictly explain to LTTng.
Could you please explain LTTng design?





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