Re: [PATCH] dtrace probes for memory manager - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [PATCH] dtrace probes for memory manager
Date
Msg-id 21712.1260557776@sss.pgh.pa.us
Whole thread Raw
In response to Re: [PATCH] dtrace probes for memory manager  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: [PATCH] dtrace probes for memory manager  (Zdenek Kotala <Zdenek.Kotala@Sun.COM>)
List pgsql-hackers
Robert Haas <robertmhaas@gmail.com> writes:
> As far as I am concerned that is way too much, particularly
> considering that your test case isn't designed to be particularly
> memory-allocation intensive, and if it is up to me I will reject this.
>  Even a quarter-percent slowdown for a feature that will be used only
> by a small fraction of users only a small fraction of time time seems
> totally unacceptable to me.

It seems to me that anyone who really needs this can instrument the
alloc functions anyway --- isn't one of the features of DTrace supposed
to be that you can monitor calls to a particular function without any
prearranged code support?  Or is that one of the things like "zero
overhead" that turns out to be more marketing-speak than reality?

Anyway I concur with Robert's opinion that the use-case is far too small
to justify incurring a measurable overhead for everybody.  There might
be some small argument for putting these in under an extra #ifdef, but
they wouldn't get into any regular production build.
        regards, tom lane


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