Re: [Jfs-discussion] benchmark results

Christian Kujau
2009-12-25T18:50:31Z

On Fri, 25 Dec 2009 at 08:22, Larry McVoy wrote:
> Dudes, sync() doesn't flush the fs cache, you have to unmount for that.

Thanks Larry, that was exactly my point[0] too, I should add that to the
results page to avoid further confusion or misassumptions:

> Well, I do "sync" after each operation, so the data should be on
> disk, but that doesn't mean it'll clear the filesystem buffers
> - but this doesn't happen that often in the real world too.

I realize however that on the same results page the bonnie++ tests were
run with a filesize *specifically* set to not utilize the filesystem
buffers any more but the measure *disk* performance while my "generic*
tests do something else - and thus cannot be compared to the bonnie++ or
hdparm results.

> No idea if that is still supported, but sync() is a joke for benchmarking.

I was using "sync" to make sure that the data "should" be on the disks
now, I did not want to flush the filesystem buffers during the "generic"
tests.

Thanks,
Christian.

[0] http://www.spinics.net/lists/linux-ext4/msg16878.html
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