From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
The per-cpu-pageset code has two distinct ways of being set up:
1. The boot-time code (the defaults that everybody runs with)
calculates a batch size, then sets pcp->high to 6x that
batch size.
2. The percpu_pagelist_fraction sysctl code takes a pcp->high
value in from userspace and sets pcp->batch value to 1/4
of the ->high value.
The crummy part is that those are called pageset_set_batch() and
pageset_set_high(), respectively. Those names make it sound
awfully like high *OR* batch is being set, when actually both
are being set.
This patch renames those two setup functions to be more clear in
what they are doing:
1. pageset_setup_from_batch_size(batch)
2. pageset_setup_from_high_mark(high)
The "max(1UL, 1 * batch)" construct was from Christoph Lameter in
commit 2caaad41. I'm not quite sure what the purpose of the
"1 * batch" is. Considering that 'batch' is unsigned, the only
value the max() could be correcting is 0. Just make the check a
plain old if() so that it is a bit less obtuse.
Note: pageset_setup_from_high_mark() does not survive this
series. I change it here for clarity and parity with its twin
even though I eventually kill it.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---
linux.git-davehans/mm/page_alloc.c | 33 +++++++++++++++++++++------------
1 file changed, 21 insertions(+), 12 deletions(-)
diff -puN mm/page_alloc.c~rename-pageset-functions mm/page_alloc.c
--- linux.git/mm/page_alloc.c~rename-pageset-functions 2013-10-15 09:57:05.870612107 -0700
+++ linux.git-davehans/mm/page_alloc.c 2013-10-15 09:57:05.875612329 -0700
@@ -4136,10 +4136,18 @@ static void pageset_update(struct per_cp
pcp->batch = batch;
}
-/* a companion to pageset_set_high() */
-static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
+/*
+ * Set the batch size for hot per_cpu_pagelist, and derive
+ * the high water mark from the batch size.
+ */
+static void pageset_setup_from_batch_size(struct per_cpu_pageset *p,
+ unsigned long batch)
{
- pageset_update(&p->pcp, 6 * batch, max(1UL, 1 * batch));
+ unsigned long high;
+ high = 6 * batch;
+ if (!batch)
+ batch = 1;
+ pageset_update(&p->pcp, high, batch);
}
static void pageset_init(struct per_cpu_pageset *p)
@@ -4158,15 +4166,15 @@ static void pageset_init(struct per_cpu_
static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
{
pageset_init(p);
- pageset_set_batch(p, batch);
+ pageset_setup_from_batch_size(p, batch);
}
/*
- * pageset_set_high() sets the high water mark for hot per_cpu_pagelist
- * to the value high for the pageset p.
+ * Set the high water mark for the per_cpu_pagelist, and derive
+ * the batch size from this high mark.
*/
-static void pageset_set_high(struct per_cpu_pageset *p,
- unsigned long high)
+static void pageset_setup_from_high_mark(struct per_cpu_pageset *p,
+ unsigned long high)
{
unsigned long batch = max(1UL, high / 4);
if ((high / 4) > (PAGE_SHIFT * 8))
@@ -4179,11 +4187,11 @@ static void __meminit pageset_set_high_a
struct per_cpu_pageset *pcp)
{
if (percpu_pagelist_fraction)
- pageset_set_high(pcp,
+ pageset_setup_from_high_mark(pcp,
(zone->managed_pages /
percpu_pagelist_fraction));
else
- pageset_set_batch(pcp, zone_batchsize(zone));
+ pageset_setup_from_batch_size(pcp, zone_batchsize(zone));
}
static void __meminit zone_pageset_init(struct zone *zone, int cpu)
@@ -5781,8 +5789,9 @@ int percpu_pagelist_fraction_sysctl_hand
unsigned long high;
high = zone->managed_pages / percpu_pagelist_fraction;
for_each_possible_cpu(cpu)
- pageset_set_high(per_cpu_ptr(zone->pageset, cpu),
- high);
+ pageset_setup_from_high_mark(
+ per_cpu_ptr(zone->pageset, cpu),
+ high);
}
mutex_unlock(&pcp_batch_high_lock);
return 0;
_
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>