checkpoints to often

checkpoints to often

[krzf83@gmail.com]

There should be a way to make automatic checkpoints less frequent. On
the busy ssd I have about 7 cp every second. If it were for example
once every 5 minutes then one could set garbage removal every few
days.
Also garbage removal should have option to clean only if like 90% of
drive is used. there is no need to remove cp-s when there is still
many GB of space left.

Re: checkpoints to often

[Chris Mason]

Excerpts from krzf83@gmail.com's message of 2011-03-31 10:30:51 -0400:
> There should be a way to make automatic checkpoints less frequent. On
> the busy ssd I have about 7 cp every second. If it were for example
> once every 5 minutes then one could set garbage removal every few
> days.
> Also garbage removal should have option to clean only if like 90% of
> drive is used. there is no need to remove cp-s when there is still
> many GB of space left.

I'm wondering how you're measuring check points?  Btrfs does a
transaction commit ever 30 seconds, so finding 7 commits per second
seems strange.

We do have a lighter weight commit that is done for fsyncs, but this is
not a full check point.

There's no garbage removal in btrfs, we use reference counting instead
of a traditional log structured design.

-chris

checkpoints to often

[krzf83-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]

There should be a way to make automatic checkpoints less frequent. On
the busy ssd I have about 7 cp every second. If it were for example
once every 5 minutes then one could set garbage removal every few
days.
Also garbage removal should have option to clean only if like 90% of
drive is used. there is no need to remove cp-s when there is still
many GB of space left.
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Re: checkpoints to often

[Ryusuke Konishi]

On Thu, 31 Mar 2011 21:19:27 +0200, "krzf83-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org " wrote:
> There should be a way to make automatic checkpoints less frequent. On
> the busy ssd I have about 7 cp every second. If it were for example
> once every 5 minutes then one could set garbage removal every few
> days.

If your application does't issue fsync, this can be done by increasing
"commit-interval" and "watermark" parameters:

The commit-interval is creation cycle of checkpoints while there is
some change.  The watermark is a threshold count of dirty data blocks.
When the number of dirty blocks exceeds this threshold, a checkpoint
creation will be triggered.

These parameters are adjustable by "nilfs-tune" tool which is included
in the recent nilfs-utils.  For instance, you can change the
commit-interval to 60 seconds by

  # nilfs-tune -i 60 /dev/sdb1

where /dev/sdb1 is the target nilfs partition.

And, watermark is ajustable by

  # nilfs-tune -m <watermark> /dev/sdb1


See manpage of nilfs-tune for details.

> Also garbage removal should have option to clean only if like 90% of
> drive is used. there is no need to remove cp-s when there is still
> many GB of space left.

The cleaner included in the recent nilfs-utils already supports this
feature.


Thanks,
Ryusuke Konishi
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