Perlbal reproxied downloads stalling

Sam G ceptorial at
Fri Sep 8 10:37:41 UTC 2006

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  

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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