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Re: Journal Usage


On Fri, Nov 02, 2001 at 06:36:00PM -0800, Mike Fedyk wrote:
> I have a large journal of 400MB (the max for 4k blocks), and I'd like to be
> able to check how much of it is being used.

Hmm.  At the moment you can't, but it wouldn't be hard to add a
debugging log message when we commit blocks to tell you that.  We
already emit information about the sequence numbers in use in the
journal at the end of commit, and adding output for blocks in use
would be easy.

> If it's not being used that much, I'd like to know if the writes *from* the
> journal to the rest of the disk could be delayed until a certain percentage
> of the journal has been used.

They already are to a certain extent, but eventually the normal
kupdated() writeback will get them.  Playing with the numbers there to
defer that writeback for longer is on the todo list.  Of course, the
longer you wait, the longer the latency for journal activity becomes
when you do eventually wrap the journal and have to wait for all the
writebehind to complete.

> It would be nice to be able to get more contiguous writes to the journal for
> bursty types of loads...

It should already be pretty contiguous.


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