RE: [PATCH 1/2] sched/wait: Break up long wake list walk

[Liang, Kan]

> On Fri, Aug 18, 2017 at 02:20:38PM +0000, Liang, Kan wrote:
> > > Nothing fancy other than needing a comment if it works.
> > >
> >
> > No, the patch doesn't work.
> >
> 
> That indicates that it may be a hot page and it's possible that the page is
> locked for a short time but waiters accumulate.  What happens if you leave
> NUMA balancing enabled but disable THP?  

No, disabling THP doesn't help the case.

Thanks,
Kan

> Waiting on migration entries also
> uses wait_on_page_locked so it would be interesting to know if the problem
> is specific to THP.
> 
> Can you tell me what this workload is doing? I want to see if it's something
> like many threads pounding on a limited number of pages very quickly. If it's
> many threads working on private data, it would also be important to know
> how each buffers threads are aligned, particularly if the buffers are smaller
> than a THP or base page size. For example, if each thread is operating on a
> base page sized buffer then disabling THP would side-step the problem but
> THP would be false sharing between multiple threads.
> 
> 
> --
> Mel Gorman
> SUSE Labs