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Re: Some newbie questions


Hi -

On Wed, Aug 17, 2016 at 09:30:38PM +0300, Avi Kivity wrote:
> [...]
> >>My load indeed calls epoll_wait() at a high rate, with zero timeout.
> >[...]
> Yes.  It's not very common, but some high throughput or latency 
> sensitive applications will poll.  In my case it's both high throughput 
> and latency sensitive.

Interesting.  I assume you've measured that.


> [...]
> >looks for mmap/exec syscalls.  Perhaps there could be a mode (a -D
> >setting?)  for selecting kprobes rather than syscall-tracepoints to
> >catch those events.
> 
> Why not trace just mmap and exec syscalls, rather than everything? 
> Surely there's a static tracepoint for those.

Heh, in this case it's "surely not".  :-) There exists only a
multiplexed system-call-entry and a system-call-exit pair of
tracepoints.


> I'd say defaulting to taking a spinlock on every syscall is going to 
> cause anyone who's using more than a laptop a lot of pain.

There may well exist optimization opportunities that would benefit
syscall-saturated applications such as yours.


- FChE


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