On Tue, Mar 12, 2013 at 12:19:13PM -0400, Theodore Ts'o wrote:
> On Tue, Mar 12, 2013 at 03:11:23PM +0100, Lukáš Czerner wrote:
> > So there is indeed a problem with the mentioned commit
> >
> > 67a5da564f97f31c4054d358e00b34d7ee570da5
> >
> > Due to the bug in that code is has exactly the opposite result -
> > with this commit we will _never_ zero out blocks instead of creating
> > uninitialized extents. In other words, we will always create
> > uninitialized extent.
>
> Whoops. I even remember how this bug happened. Originally
> max_zeroout was in file system blocks, and it was suggested that we
> change this to use units of kilobytes instead. Unfortunately, this
> change wasn't done completely. :-(
>
> > This can be easily fixed by the following patch (which makes the
> > warning go away), but it brings up a question whether this "optimization"
> > was worth it in the first place since noone noticed that it had exactly
> > the opposite effect than it should have had :)
>
> Well, I had noticed that random AIO workloads resulted in the extent
> tree getting far more fragmented than I had expected. (See previous
> discusisons about how we really need to improve our ability to merge
> empty leaf and index nodes in the extent tree.)
Agree, we could do better in merging extent tree. I will take a look at
it, but, sorry, my plate is too full recently. So it has a low priority.
Regards,
- Zheng
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
