Re: Processes spinning forever, apparently in lock_timer_base()?

[Chuck Ebbert <cebbert@redhat.com>]

On 09/21/2007 11:58 AM, Hugh Dickins wrote:
> Looking at the 2.6.18-2.6.23 code, I'm uncertain what to try instead.
> There is a refresh_vm_stats function which we could call (then retest
> the break condition) just before resorting to congestion_wait.  But
> the big NUMA people might get very upset with me calling that too
> often: causing a thundering herd of bouncing cachelines which that
> was all designed to avoid.  And it's not obvious to me what condition
> to test for dirty_thresh "too low".
> 
> I believe Peter gave all this quite a lot of thought when he was
> making the rc6-mm1 changes, and I'd rather defer to him for a
> suggestion of what best to do in earlier releases.  Or maybe he'll
> just point out how this couldn't have been a problem before.
> 
> Or there is is Richard's patch, which I haven't considered, but
> Andrew was not quite satisfied with it - partly because he'd like
> to understand how the situation could come about first, perhaps
> we have now got an explanation.
> 

My patch is just Richard's with the added requirement that we loop
some minimum number of times before exiting balance_dirty_pages()
with unfinished work.