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

Dave Hansen
2021-05-21T22:57:29Z

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@linux.intel.com>