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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-04-02 16:57:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-02 19:04:56 -0700
commita3b2d692690aef228e493b1beaafe5364cab3237 (patch)
treed3ad99c5370462861a1b918b4136e7bd7ad78e52 /mm/page_cgroup.c
parent3c776e64660028236313f0e54f3a9945764422df (diff)
downloadlinux-a3b2d692690aef228e493b1beaafe5364cab3237.tar.bz2
cgroups: use css id in swap cgroup for saving memory v5
Try to use CSS ID for records in swap_cgroup. By this, on 64bit machine, size of swap_cgroup goes down to 2 bytes from 8bytes. This means, when 2GB of swap is equipped, (assume the page size is 4096bytes) From size of swap_cgroup = 2G/4k * 8 = 4Mbytes. To size of swap_cgroup = 2G/4k * 2 = 1Mbytes. Reduction is large. Of course, there are trade-offs. This CSS ID will add overhead to swap-in/swap-out/swap-free. But in general, - swap is a resource which the user tend to avoid use. - If swap is never used, swap_cgroup area is not used. - Reading traditional manuals, size of swap should be proportional to size of memory. Memory size of machine is increasing now. I think reducing size of swap_cgroup makes sense. Note: - ID->CSS lookup routine has no locks, it's under RCU-Read-Side. - memcg can be obsolete at rmdir() but not freed while refcnt from swap_cgroup is available. Changelog v4->v5: - reworked on to memcg-charge-swapcache-to-proper-memcg.patch Changlog ->v4: - fixed not configured case. - deleted unnecessary comments. - fixed NULL pointer bug. - fixed message in dmesg. [nishimura@mxp.nes.nec.co.jp: css_tryget can be called twice in !PageCgroupUsed case] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Paul Menage <menage@google.com> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_cgroup.c')
-rw-r--r--mm/page_cgroup.c32
1 files changed, 14 insertions, 18 deletions
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index ceecfbb143fa..ebf81074bed4 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -285,12 +285,8 @@ struct swap_cgroup_ctrl {
struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
-/*
- * This 8bytes seems big..maybe we can reduce this when we can use "id" for
- * cgroup rather than pointer.
- */
struct swap_cgroup {
- struct mem_cgroup *val;
+ unsigned short id;
};
#define SC_PER_PAGE (PAGE_SIZE/sizeof(struct swap_cgroup))
#define SC_POS_MASK (SC_PER_PAGE - 1)
@@ -342,10 +338,10 @@ not_enough_page:
* @ent: swap entry to be recorded into
* @mem: mem_cgroup to be recorded
*
- * Returns old value at success, NULL at failure.
- * (Of course, old value can be NULL.)
+ * Returns old value at success, 0 at failure.
+ * (Of course, old value can be 0.)
*/
-struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem)
+unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
{
int type = swp_type(ent);
unsigned long offset = swp_offset(ent);
@@ -354,18 +350,18 @@ struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem)
struct swap_cgroup_ctrl *ctrl;
struct page *mappage;
struct swap_cgroup *sc;
- struct mem_cgroup *old;
+ unsigned short old;
if (!do_swap_account)
- return NULL;
+ return 0;
ctrl = &swap_cgroup_ctrl[type];
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
- old = sc->val;
- sc->val = mem;
+ old = sc->id;
+ sc->id = id;
return old;
}
@@ -374,9 +370,9 @@ struct mem_cgroup *swap_cgroup_record(swp_entry_t ent, struct mem_cgroup *mem)
* lookup_swap_cgroup - lookup mem_cgroup tied to swap entry
* @ent: swap entry to be looked up.
*
- * Returns pointer to mem_cgroup at success. NULL at failure.
+ * Returns CSS ID of mem_cgroup at success. 0 at failure. (0 is invalid ID)
*/
-struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent)
+unsigned short lookup_swap_cgroup(swp_entry_t ent)
{
int type = swp_type(ent);
unsigned long offset = swp_offset(ent);
@@ -385,16 +381,16 @@ struct mem_cgroup *lookup_swap_cgroup(swp_entry_t ent)
struct swap_cgroup_ctrl *ctrl;
struct page *mappage;
struct swap_cgroup *sc;
- struct mem_cgroup *ret;
+ unsigned short ret;
if (!do_swap_account)
- return NULL;
+ return 0;
ctrl = &swap_cgroup_ctrl[type];
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
- ret = sc->val;
+ ret = sc->id;
return ret;
}
@@ -432,7 +428,7 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
printk(KERN_INFO
"swap_cgroup: uses %ld bytes of vmalloc for pointer array space"
- " and %ld bytes to hold mem_cgroup pointers on swap\n",
+ " and %ld bytes to hold mem_cgroup information per swap ents\n",
array_size, length * PAGE_SIZE);
printk(KERN_INFO
"swap_cgroup can be disabled by noswapaccount boot option.\n");