RE: [Xen-devel] tap:aio performance

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> Now that I have tap:aio working under GPLPV, I have found that the
> performance is terrible (as in something is wrong). Under any sort of
> load, the system becomes effectively frozen - block requests appear to
> be taking seconds.
> 
> Currently I have up to 16 requests 'in the air' at a time... is that
too
> much for tap:aio? Is there something else I could be doing wrong?
> 
> It's got me baffled at the moment...
> 

This continues to frustrate me. I thought maybe using 'sparse' files to
back tap:aio might be causing problems so I freed up some space and
created a non-sparse file, but that didn't change anything.

The backup exec restore fly's along at about 600mb/min until it has
restored about 500mb and then it drops to about 12mb/min, and the DomU
is effectively unusable (anything that needs disk activity takes forever
to get there...). Once the restore finally cancel's (this takes a long
time too) the performance comes back to being usable.

Next I'll try it under Linux instead of GPLPV... but I can't think why
that would make a difference...

James

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