[PATCH RFC] Summary of syscall latency

[Dmitry V. Levin]

On Tue, May 20, 2014 at 10:26:11AM +0100, Mark Hills wrote:
> Time spent in system time is not useful where a syscall depends on some 
> non-CPU resource, eg. typically open() or stat() to a network drive.
> 
> This patch adds a -w flag to produce a summary of the time difference 
> between beginning and end of the system call (ie. latency)
> 
> This functionality has been useful to profile slow processes that are not 
> CPU-bound.
> 
> An older commit 8050cdc mentions this:
> 
> > It might be useful to have a mode where we show wall clock time spent in 
> > syscalls, not CPU time. It might also be more accurate.
> 
> I'm not sure how reasonably useful the crude profile of CPU "system time" 
> is. Is it better to replace the existing functionality with 
> wallclock/latency time, or does this justify the introduction of a new 
> flag, as below?

I think a new behavior justifies a new flag.  Another option is to treat
the same -c/-C option given twice as a request for this new behavior.


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