Re: [PATCH 1/1] mm: vmscan: Reduce throttling due to a failure to make progress

Mel Gorman
2021-11-30T13:09:42Z

On Tue, Nov 30, 2021 at 01:51:10PM +0100, Mike Galbraith wrote:
> On Tue, 2021-11-30 at 13:00 +0100, Mike Galbraith wrote:
> > On Tue, 2021-11-30 at 11:22 +0000, Mel Gorman wrote:
> > > On Tue, Nov 30, 2021 at 11:14:32AM +0100, Mike Galbraith wrote:
> > > > >       }
> > > > > +       if (2 * write_pending <= reclaimable)
> > > >
> > > > That is always true here...
> > > >
> > >
> > > Always true for you or always true in general?
> >
> > "Here" as in the boxen located at my GPS coordinates :)
> >
> > > The intent of the check is "are a majority of reclaimable pages
> > > marked WRITE_PENDING?". It's similar to the check that existed prior
> > > to 132b0d21d21f ("mm/page_alloc: remove the throttling logic from the
> > > page allocator").
> >
> > I'll put my trace_printk() back and see if I can't bend-adjust it.
>
> As it sits, write_pending is always 0 with tail /dev/zero.
>

That is not a surprise for the test in question as it doesn't trigger
a case where there are lots of page cache being marked dirty and write
pending.

--
Mel Gorman
SUSE Labs