Questions on nilfs_cleanerd

Questions on nilfs_cleanerd

[Kenneth Langga]

1) Does the daemon read/write the entire drive to look for dead blocks to clean?

2) What if there aren't any dead blocks to clean and the free space in
the drive is still less than 10% (the default min_clean_segments in
the conf file), does the daemon still process the drive? If so, how do
I change the cleaning interval so that it doesn't process the drive as
often?
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Re: Questions on nilfs_cleanerd

[Gordan Bobic]

These sound similar to the questions/concerns I raised a while back.

> 1) Does the daemon read/write the entire drive to look for dead blocks to clean?

Yes - sequentially (and then it rolls over to the beginning again).

> 2) What if there aren't any dead blocks to clean and the free space in
> the drive is still less than 10% (the default min_clean_segments in
> the conf file), does the daemon still process the drive? If so, how do
> I change the cleaning interval so that it doesn't process the drive as
> often?

The only worthwhile suggestion I heard is to set the minimum history 
retention rate (the FS is continuously snapshotting) to 1 day. That way 
you can guarantee the churn rate will never exceed the capacity of the 
disk per day. Not ideal, but at least it puts some kind of a hard limit 
on how quickly it'll waste your flash - at the expense of making the 
problem of the non-determinism of free space a little worse.

Gordan
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