Re: ebizzy performance with different allocators

["Valerie Henson" <val@vahconsulting.com>]

[Cc'd current ebizzy maintainer, Rodrigo.]

On Mon, Mar 17, 2008 at 5:21 AM, Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Hi,
>
>  I was recently interested in ebizzy performance, and specifically the
>  reason why Linux doesn't appear to scale very well versus FreeBSD.

[snip]

>  linux-glibc was the best single-threaded performer, with ~7000 r/s,
>  however it starts running into system time which the profile shows up
>  as unmapping pages and faulting in new pages. Is "fixing" this as simple
>  as increasing hysteresis in glibc? Can that be done via environment? (I
>  couldn't work out a way).

Huh, yeah, that sounds like glibc is mmap()'ing your allocations.
Check to see if your glibc version includes this patch:

http://www.valhenson.org/patches/dynamic_mmap_threshold

If it does, you shouldn't see much in the way of mmap/munmap activity
when running ebizzy.  It's possible that some other malloc() settings
are interfering, maybe the trim threshold.  It's also worth noting
that the self-tuning mmap threshold is disabled if the user sets the
mmap threshold explicitly.  Oh, and is this 32-bit or 64-bit?

If you want to tune the exact behavior of malloc with regard to mmap, check out:

http://www.gnu.org/software/libtool/manual/libc/Malloc-Tunable-Parameters.html

If you use the "-M" option to ebizzy, it will use mallopt() to turn
off mmap()'d allocations entirely. (It'd be nice to have command line
knobs for all the mallopt() tuning options, actually.)

-VAL

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