Re: [PATCH 6/6] mm/page_alloc: Introduce vm.percpu_pagelist_high_fraction

[Dave Hansen]

On 5/21/21 3:28 AM, Mel Gorman wrote:
> This introduces a new sysctl vm.percpu_pagelist_high_fraction. It is
> similar to the old vm.percpu_pagelist_fraction except it only adjusts
> pcp->high to potentially reduce zone->lock contention while preserving
> allocation latency when PCP lists have to be refilled.

Look at me...  Five patches later and I already forgot what the old one
did and why it stinks.  I wonder if you might do a wee bit of compare
and contrast.  Something like:

	The old vm.percpu_pagelist_fraction increased both the batch and
	high limits for the per-cpu page allocator.  Its worst feature
	was that it led to absurdly large batch sizes that incurred
	nasty worst-case allocation latency.

	This new sysctl in comparison...

Anyway, the approach looks sound to me.  The batch size isn't important
now, especially given the auto-scaling in patch 4.

Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>