Re: trying to understand READ_META, READ_SYNC, WRITE_SYNC & co

From: Christoph Hellwig
Date: Sat Jun 26 2010 - 05:28:19 EST

On Sat, Jun 26, 2010 at 07:25:56PM +1000, Nick Piggin wrote:
> Biggest thing is multiple small files operations like on the same
> directory. Best case I measured back when doing AS io scheduler
> versus deadline was about 100x improvement on a uncached kernel
> grep workload when competing with a streaming writeout (the writeout
> probably ended up going somewhat slower naturally, but it is fairer).

As I mentioned below I absolutely see the case for reads. A normal
grep basically is a dependent read kind of workload. For for writes
it should either be O_SYNC-style workloads or batched I/O.
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