Re: Hot rb_next, setup_cluster_no_bitmap

Simon Kirby
2011-08-04T17:28:35Z

On Thu, Aug 04, 2011 at 10:04:29AM -0400, Chris Mason wrote:

> Excerpts from Simon Kirby''s message of 2011-08-03 21:32:10 -0400:
> > Perhaps as a further clue as to what is going on, on this same backup
box
> > after all of the rsyncs are finished/killed and a good amount of time
has
> > passed (no cleaner processes running in the background or anything),
> > "sync" is still consistently takes ~4 minutes to run, and
pushes out a
> > lot to disk every time it is run. Example:
> >
> > echo 3 > /proc/sys/vm/drop_caches
> > sync
> > echo 3 > /proc/sys/vm/drop_caches
> > sync
> > vmstat 1 &
> > time sync
>
> Just to confirm, the profiling during this time shows your system time
> is all in rb_next?

Correct, rb_next() called from setup_cluster_no_bitmap(). Also, much of the
other CPU time is spent spinning (on refill_lock, I think).

It''s in this state again now (just one overnight backup run does it).
It
doesn''t seem to happen for the first few hours, but shows up by the
next
morning.