Re: [PATCH] mm: vmpressure: fix scan window after SWAP_CLUSTER_MAX increase

[Johannes Weiner <hannes@cmpxchg.org>]

On Mon, Oct 19, 2015 at 02:13:01PM -0400, Johannes Weiner wrote:
> mm-increase-swap_cluster_max-to-batch-tlb-flushes.patch changed
> SWAP_CLUSTER_MAX from 32 pages to 256 pages, inadvertantly switching
> the scan window for vmpressure detection from 2MB to 16MB. Revert.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> ---
>  mm/vmpressure.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> index c5afd57..74f206b 100644
> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -38,7 +38,7 @@
>   * TODO: Make the window size depend on machine size, as we do for vmstat
>   * thresholds. Currently we set it to 512 pages (2MB for 4KB pages).
>   */
> -static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16;
> +static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX;

Argh, Mel's patch sets SWAP_CLUSTER_MAX to 256, so this should be
SWAP_CLUSTER_MAX * 2 to retain the 512 pages scan window.

Andrew could you please update this fix in-place? Otherwise I'll
resend a corrected version.

Thanks, and sorry about that.

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