Re: [PATCH] dtrace probes for memory manager

--On 10. Dezember 2009 23:55:49 -0500 Robert Haas <robertmhaas@gmail.com> 
wrote:

> If there's some real-world test where this probe costs 0.3%-0.4%, I
> think that is sufficient grounds for rejecting this patch.  I
> understand the desire of people to be able to use dtrace, but our
> performance is too hard-won for me to want to give any measurable of
> it up for tracing and instrumentation hooks that will only be used by
> a small number of users in a small number of situations.

I repeated the pgbench runs per Greg's advice (see upthread) and it seems 
there is actually a small slowdown which supports this argument, 
unfortunately. After repeating the pgbench runs with and without the new 
probes (note: i've used the new version of the patch, too), the numbers are 
going to stabilize as follows:

without compiled probes: AVG(2531.68)
with compiled probes: AVG(2511.97)

I can repeat that tests over and over, but this doesn't seem to change the 
whole picture (so there seems some real argument for a 0.4 - 0.6% cost, at 
least on *my* machine here with pgbench).

-- 
Thanks
Bernd