Re: memory caching

[Jens Axboe <jaxboe@xxxxxxxxxxxx>]

On 2011-03-15 21:46, N. Harake wrote:
> 
> Thanks for your reply, indeed my interest to get the max iops but on a
> filesystem not a raw device, I understand the penalty but that would
> be more realstic for production systems. I will try these changes and
> keep you updated .

It's always a good idea to do the raw block device test first, that'll
at least give you an idea of the best possible result. On a file system,
you'll get the best results with O_DIRECT if the file has been
pre-allocated first. Otherwise you end up punting to buffered IO for
filling new blocks.

So that would mean adding --overwrite=1. And get rid of the O_SYNC. If
your workload will utilize lots of processes or threads, use what you
already have with a high numjobs. But an libaio with fewer threads and
higher depth will get you better performance.

-- 
Jens Axboe

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