Perlbal reproxied downloads stalling

Brad Fitzpatrick brad at
Fri Sep 8 17:47:33 UTC 2006

Hm.  Can you get an strace on the main Perlbal process while this is

$ strace -s 500 -o perlbal.trace -p <pid-of-perlbal>
...... (wait)

On Fri, 8 Sep 2006, Sam G wrote:

> Hi all,
> I have perlbal installed on a Centos 4.4 x64 dual Opteron server w/ 4GB
> RAM, and am reproxying from a webserver to read files from a clustered
> storage backend running Apache/DAV. When I do a reproxied download, things
> seem to go well until a few megabytes into the file; then, the download
> seems to slow down sharply then hang. It will happen at different parts of
> the file, but the speed always starts out strong (500kb/s to 2mb/s,
> depending on the connection I'm downloading from) but after 10 seconds or
> so comes to a halt. Sometimes it'll slow way down, speed back up, but then
> slow down again, finally hanging. This happens for virtually any large
> file.
> I've tried both 'ioaio' and 'none' for the aio_mode parameter (Linux::IO
> won't pass tests), but same thing happens in both cases. I can pull from
> the storage to the perlbal machine no problem with HTTP wget, at about 30
> MB/s uninterrupted. As the reeproxied download happens, perlbal CPU usage
> never goes above 1%. I have the default buffer settings; have tried
> tweaking a little but to no avail.
> Anyone have any ideas why this might be happening?
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