Re: [PATCH -mm] vmscan: make mapped executable pages the first class citizen

KOSAKI Motohiro
2009-05-10T08:59:29Z

2009/5/9 Alan Cox <alan@lxorguk.ukuu.org.uk>:
>> The patch seems reasonable but the changelog and the (non-existent)
>> design documentation could do with a touch-up.
>
> Is it right that I as a user can do things like mmap my database
> PROT_EXEC to get better database numbers by making other
> stuff swap first ?
>
> You seem to be giving everyone a "nice my process up" hack.

How about this?
if priority < DEF_PRIORITY-2, aggressive lumpy reclaim in
shrink_inactive_list() already
reclaim the active page forcely.
then, this patch don't change kernel reclaim policy.

anyway, user process non-changable preventing "nice my process up
hack" seems makes sense to me.

test result:

echo 100 > /proc/sys/vm/dirty_ratio
echo 100 > /proc/sys/vm/dirty_background_ratio
run modified qsbench (use mmap(PROT_EXEC) instead malloc)

active2active vs active2inactive ratio
before 5:5
after 1:9

please don't ask performance number. I haven't reproduce Wu's patch
improvemnt ;)

Wu, What do you think?

---
mm/vmscan.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

Index: b/mm/vmscan.c
===================================================================
--- a/mm/vmscan.c 2009-05-10 02:40:01.000000000 +0900
+++ b/mm/vmscan.c 2009-05-10 03:33:30.000000000 +0900
@@ -1275,7 +1275,8 @@ static void shrink_active_list(unsigned
struct address_space *mapping = page_mapping(page);

pgmoved++;
- if (mapping && test_bit(AS_EXEC, &mapping->flags)) {
+ if (mapping && (priority >= DEF_PRIORITY - 2) &&
+ test_bit(AS_EXEC, &mapping->flags)) {
pga2a++;
list_add(&page->lru, &l_active);
continue;