On Mon, Aug 28, 2006 at 01:31:32PM +1000, Nathan Scott wrote:
> Hi,
>
> While testing something else recently, I noticed we were always
> creating a large number of unwritten extents during page cache
> writout to the realtime subvolume. It turned out to be because
> of the way we are typically called with page sized allocation
> requests, but we always allocate much more than a page. Back
> when realtime subvols could only use direct I/O this was fine
> (apps typically used larger IO sizes) but now its not so good.
>
> These larger allocations are ending up meaning we need to do many
> additional unwritten extent conversions (i.e. more transactions,
> and more log traffic), which we can easily avoid. Since we have
> a default 4K filesystem blocksize on the data device, there would
> seem to be no harm in matching that on the realtime subvolume, by
> default. This simple mkfs tweak does just that...
That description makes sense, and given that the one-liner diff is
obviously correct. ACK from me.
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