Re: throttling dirtiers

Andrew Morton
2002-07-31T22:24:28Z

Rik van Riel wrote:
>
> On Wed, 31 Jul 2002, Andrew Morton wrote:
>
> > > These ingredients are already in 2.4-rmap.
> >
> > It doesn't seem to work. The -ac kernel has weird stalls on
> > storms of ext3 writeback.
>
> Maybe you shouldn't have cut off the other line from my
> 2-line mail ;)))
>
> The most probable reason for the stalls is the fact that
> page_launder (like shrink_cache) will try to write out
> the complete inactive list if it's almost full of dirty
> pages, so the system will still be stuck in __get_request_wait
> seconds after the first few megabytes of the paged out
> inactive pages have been cleaned already.

I doubt if it's that, although it might be.

It happens just during a kernel build, 768M of RAM. And/or
during big CVS operations. Possibly it's due to ext3 checkpointing.
In ordered data mode with these workloads, kupdate should normally
be doing that, so it may be a kupdate problem, or a missing
wakeup_bdflush.

It's not a big issue - people would be unlikely to notice unless
they were switching between kernels, and were ravingly impatient,
like me.