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SubjectRe: filesystem benchmarking fun
On Wed, May 16, 2007 at 01:04:13PM -0700, Andrew Morton wrote:
> > The good news is that if you let it run long enough, the times
> > stabilize. The bad news is:
> >
> > create dir kernel-86 222MB in 15.85 seconds (14.03 MB/s)
> > create dir kernel-87 222MB in 28.67 seconds (7.76 MB/s)
> > create dir kernel-88 222MB in 18.12 seconds (12.27 MB/s)
> > create dir kernel-89 222MB in 19.77 seconds (11.25 MB/s)
>
> well hang on. Doesn't this just mean that the first few runs were writing
> into pagecache and the later ones were blocking due to dirty-memory limits?
>
> Or do you have a sync in there?
>
There's no sync, but if you watch vmstat you can clearly see the log
flushes, even when the overall create times are 11MB/s. vmstat goes
30MB/s -> 4MB/s or less, then back up to 30MB/s.

On the same box, my shiny new FS writes at 30MB/s the whole time. For
this part of the benchmark, I think we should all be getting the same
numbers.

-chris

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