Re: mm-set-per-cpu-pages-lower-threshold-to-zero.patch added to -mm tree

[Nick Piggin <nickpiggin@yahoo.com.au>]

akpm@osdl.org wrote:

>The patch titled
>
>     mm: set per-cpu-pages lower threshold to zero
>
>has been added to the -mm tree.  Its filename is
>
>     mm-set-per-cpu-pages-lower-threshold-to-zero.patch
>
>
>From: "Seth, Rohit" <rohit.seth@intel.com>
>
>Set the low water mark for hot pages in pcp to zero.
>
>(akpm: for the life of me I cannot remember why we created pcp->low.  Neither
>can Martin and the changelog is silent.  Maybe it was just a brainfart, but I
>have this feeling that there was a reason.  If not, we should remove the
>fields completely.  We'll see.)
>
>  
>

I think it is bogus. Andrea did too IIRC.

>Signed-off-by: Rohit Seth <rohit.seth@intel.com>
>Cc: <linux-mm@kvack.org>
>Signed-off-by: Andrew Morton <akpm@osdl.org>
>---
>
> mm/page_alloc.c |    4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
>diff -puN mm/page_alloc.c~mm-set-per-cpu-pages-lower-threshold-to-zero mm/page_alloc.c
>--- devel/mm/page_alloc.c~mm-set-per-cpu-pages-lower-threshold-to-zero	2005-09-12 00:21:31.000000000 -0700
>+++ devel-akpm/mm/page_alloc.c	2005-09-12 00:21:31.000000000 -0700
>@@ -1772,7 +1772,7 @@ inline void setup_pageset(struct per_cpu
> 
> 	pcp = &p->pcp[0];		/* hot */
> 	pcp->count = 0;
>-	pcp->low = 2 * batch;
>+	pcp->low = 0;
> 	pcp->high = 6 * batch;
> 	pcp->batch = max(1UL, 1 * batch);
> 	INIT_LIST_HEAD(&pcp->list);
>  
>

Can you change pcp->high to 4*batch, to match behaviour?


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