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Re: Meeting minutes 20060727

Stone, Joshua I wrote:

On Thursday, August 03, 2006 12:43 PM, Jose R. Santos wrote:

Frank Ch. Eigler wrote:

"Jose R. Santos" <> writes:

[...] One of the things we are currently working on is to have an
alternative to gettimeofday. [...]

Josh Stone's kprobes-safe rendition gettimeofday has been in the
systemtap runtime for some time now. Is that not sufficient for
your purposes?

The goal here is to improve performance. Gui Jian has timed
_stp_gettimeofday_us() using LKET and it give a bigger overhead than
do_gettimeofday(). By doing this in user space we can obtain better
performance by avoiding disabling preemption or calling seqlock like
_stp_gettimeofday does.

If you have suggestions for improving _stp_gettimeofday, I'm all ears. I'm never of the mind that the existing code is the perfect solution.

But then, if you're doing something from userspace, I guess I don't
fully understand your usage model, or how that will be faster...


During one of the BOF's in OLS the discussion of do_gettimeofday() overhead came, everyone agreed it is slow. Someone suggested that Linux now has more efficient interface to get the timestamp, my notes seems to lack details, does anyone remember what was the alternative suggestion. I vaguely recollect that either real time guys or the high resolution timer folks have introduced an interface which is platform dependent but more efficient. If anyone can recollect details of this please post it.

Vara Prasad

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