Re: [PATCH 1/2] vmscan: fix initial shrinker size handling

[Konstantin Khlebnikov]

Andrew Morton wrote:
<snip>
> >   		long new_nr;
> >   		long batch_size = shrinker->batch ? shrinker->batch
> >   						  : SHRINK_BATCH;
> >
> > +		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
> > +		if (max_pass<= 0)
> > +			continue;
> > +
> >   		/*
> >   		 * copy the current shrinker scan count into a local variable
> >   		 * and zero it so that other concurrent shrinker invocations
> > @@ -266,7 +270,6 @@ unsigned long shrink_slab(struct shrink_control *shrink,
> >   		} while (cmpxchg(&shrinker->nr, nr, 0) != nr);
> >
> >   		total_scan = nr;
> > -		max_pass = do_shrinker_shrink(shrinker, shrink, 0);
> >   		delta = (4 * nr_pages_scanned) / shrinker->seeks;
> >   		delta *= max_pass;
> >   		do_div(delta, lru_pages + 1);
>
> Why was the shrinker call moved to before the alteration of shrinker->nr?

I think, if we skip shrinker we shouldn't reset accumulated pressure,
because next reclaimer (for example with less strict gfp) can use it.
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