Re: [Moosefs-users] mfsmaster performance and hardware

[Elliot F. <efi...@gm...>]

On Tue, Aug 9, 2011 at 6:46 PM, Robert Sandilands <rsa...@ne...> wrote:
> Increasing the swap space fixed the fork() issue. It seems that you have to
> ensure that memory available is always double the memory needed by
> mfsmaster. None of the swap space was used over the last 24 hours.
>
> This did solve the extreme comb-like behavior of mfsmaster. It still does
> not resolve its sensitivity to load on the server. I am still seeing
> timeouts on the chunkservers and mounts on the hour due to the high CPU and
> I/O load when the meta data is dumped to disk. It did however decrease
> significantly.

Here is another thought on this...

The process is niced to -19 (very high priority) so that it has good
performance.  It forks once per hour to write out the metadata.  I
haven't checked the code for this, but is the forked process lowering
it's priority so it doesn't compete with the original process?

If it's not, it should be an easy code change to lower the priority in
the child process (metadata writer) so that it doesn't compete with
the original process at the same priority.

If you check into this, I'm sure the list would appreciate an update. :)

Elliot