Re: Some newbie questions

[Avi Kivity <avi at scylladb dot com>]

On 08/17/2016 09:35 PM, Frank Ch. Eigler wrote:
> 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.

Hi,

Should I wait for ongoing improvement here, or shall I look elsewhere 
for my tracing needs?

It would be a pity (for me) if I have to find another solution, because 
systemtap has all the expressiveness and integration I need.  But it has 
a dramatic impact on my application runtime.

I was able to extract some useful data with perf probe/perf record, but 
as soon as I need to qualify a probe point with runtime information, 
perf falls short.


Avi