Re: [PATCH 0/5] Improve sequential read throughput v4r8

[Mel Gorman]

On Tue, Jul 01, 2014 at 07:39:15PM +0100, Mel Gorman wrote:
> The fair zone policy itself is partially working against the lowmem
> reserve idea. The point of the lowmem reserve was to preserve the lower
> zones when an upper zone can be used and the fair zone policy breaks
> that. The fair zone policy ignores that and it was never reconciled. The
> dirty page distribution does a different interleaving again and was never
> reconciled with the fair zone policy or lowmem reserves. kswapd itself was
> not using the classzone_idx it actually woken for although in this case
> it may not matter. The end result is that the model is fairly inconsistent
> which makes comparison against it a difficult exercise at best. About all
> that was left was that from a performance perspective that the fair zone
> allocation policy is not doing the right thing for streaming workloads.
> 

The inevitable feedback will be to reconcile those differences so I'm
redid the series and queued it for testing. Patch list currently looks
like

mm: pagemap: Avoid unnecessary overhead when tracepoints are deactivated
mm: Rearrange zone fields into read-only, page alloc, statistics and page reclaim lines
mm: page_alloc: Add ALLOC_DIRTY for dirty page distribution
mm: page_alloc: Only apply the fair zone allocation policy if it's eligible
mm: page_alloc: Only apply either the fair zone or dirty page distribution policy, not both
mm: page_alloc: Reduce cost of the fair zone allocation policy
mm: page_alloc: Reconcile lowmem reserves with fair zone allocation policy
mm: vmscan: Fix oddities with classzone and zone balancing
mm: vmscan: Reconcile balance gap lowmem reclaim with fair zone allocation policy
mm: vmscan: Remove classzone considerations from kswapd decisions

About 13 hours to test for ext3 on the small machine, 3 days for the larger
machine. The test could be accelerated by either reducing the iterations or
the memory size of the machine but that would distort the results too badly.

-- 
Mel Gorman
SUSE Labs
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