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

Mel Gorman
2021-05-24T09:25:35Z

On Fri, May 21, 2021 at 03:57:20PM -0700, Dave Hansen wrote:
> 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>

Thanks, I updated the changelog and hopefully it is better.

--
Mel Gorman
SUSE Labs