Strange slowdown of zlib.
Ian Lepore
ian at FreeBSD.org
Thu Jun 19 15:59:06 UTC 2014
On Thu, 2014-06-19 at 17:44 +0200, Magnus Nilsson wrote:
> I have the strangest behaviour of zlib on FreeBSD 8.2 (ARM, but I don't
> think it's necessarily an ARM specific issue).
> Doing
> # md5 /lib/libz.so.5
> or
> # cp /lib/libz.so.5 /tmp/
> # export LD_LIBRARY_PATH=/tmp/
> slows down applications (I've tested bsdtar and gzip) using zlib to a crawl
> on my system.
>
> In the later case, doing
> # unset LD_LIBRARY_PATH
> reverts the issue.
> However, I haven't found any way to recover from the first case, apart from
> rebooting - then the execution time is back to normal.
>
> Here is a log of what I describe above (first moving zlib, then doing the
> md5):
> # cp some2MBfile /tmp/
> # time gzip /tmp/some2MBfile
> real 0m0.325s
> user 0m0.284s
> sys 0m0.037s
> # rm /tmp/some2MBfile.gz
> # cp /lib/libz.so.5 /tmp/
> # export LD_LIBRARY_PATH=/tmp/
> # cp some2MBfile /tmp/
> # time gzip /tmp/some2MBfile
> real 0m11.949s
> user 0m11.635s
> sys 0m0.035s
> # rm /tmp/some2MBfile.gz
> # unset LD_LIBRARY_PATH
> # cp some2MBfile /tmp/
> # time gzip /tmp/some2MBfile
> real 0m0.325s
> user 0m0.288s
> sys 0m0.035s
> # rm /tmp/some2MBfile.gz
> # md5 /lib/libz.so.5
> # cp some2MBfile /tmp/
> # time gzip /tmp/some2MBfile
> real 0m11.919s
> user 0m11.608s
> sys 0m0.031s
> # rm /tmp/some2MBfile.gz
>
> Do you have any idea what could be going on?
> Any clues are welcome.
>
> Kind regards/Magnus
This is a known problem on armv4/v5 in freebsd 8. Here is some archived
info on it including patches that work around the problem (rather
crudely, but good enough for our needs at $work).
http://lists.freebsd.org/pipermail/freebsd-arm/2012-January/003288.html
-- Ian
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