* [PATCH 1/2] memcg: remove unnecessary BUG_ON
@ 2011-01-11 8:51 Minchan Kim
2011-01-11 8:51 ` [PATCH 2/2] memcg: remove charge variable in unmap_and_move Minchan Kim
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Minchan Kim @ 2011-01-11 8:51 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, LKML, KAMEZAWA Hiroyuki, Balbir Singh,
Daisuke Nishimura, Minchan Kim
Now memcg in unmap_and_move checks BUG_ON of charge.
mem_cgroup_prepare_migration returns either 0 or -ENOMEM.
If it returns -ENOMEM, it jumps out unlock without the check.
If it returns 0, it can pass BUG_ON. So it's meaningless.
Let's remove it.
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
---
mm/migrate.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index b8a32da..8f0f131 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -667,7 +667,6 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
rc = -ENOMEM;
goto unlock;
}
- BUG_ON(charge);
if (PageWriteback(page)) {
if (!force || !sync)
--
1.7.0.4
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 2/2] memcg: remove charge variable in unmap_and_move
2011-01-11 8:51 [PATCH 1/2] memcg: remove unnecessary BUG_ON Minchan Kim
@ 2011-01-11 8:51 ` Minchan Kim
2011-01-12 0:38 ` Daisuke Nishimura
2011-01-12 0:48 ` KAMEZAWA Hiroyuki
2011-01-12 0:38 ` [PATCH 1/2] memcg: remove unnecessary BUG_ON Daisuke Nishimura
2011-01-12 0:47 ` KAMEZAWA Hiroyuki
2 siblings, 2 replies; 6+ messages in thread
From: Minchan Kim @ 2011-01-11 8:51 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, LKML, KAMEZAWA Hiroyuki, Balbir Singh,
Daisuke Nishimura, Minchan Kim
memcg charge/uncharge could be handled by mem_cgroup_[prepare/end]
migration itself so charge local variable in unmap_and_move lost the role
since we introduced 01b1ae63c2.
In addition, the variable name is not good like below.
int unmap_and_move()
{
charge = mem_cgroup_prepare_migration(xxx);
..
BUG_ON(charge); <-- BUG if it is charged?
..
uncharge:
if (!charge) <-- why do we have to uncharge !charge?
mem_group_end_migration(xxx);
..
}
So let's remove unnecessary and confusing variable.
Suggested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
---
mm/memcontrol.c | 1 +
mm/migrate.c | 9 +++------
2 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8ab8410..b1b572f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2804,6 +2804,7 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
/*
* Before starting migration, account PAGE_SIZE to mem_cgroup that the old
* page belongs to.
+ * Note : Should not return -EAGAIN. unmap_and_move depends on it.
*/
int mem_cgroup_prepare_migration(struct page *page,
struct page *newpage, struct mem_cgroup **ptr)
diff --git a/mm/migrate.c b/mm/migrate.c
index 8f0f131..5f2169f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -623,7 +623,6 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
struct page *newpage = get_new_page(page, private, &result);
int remap_swapcache = 1;
int rcu_locked = 0;
- int charge = 0;
struct mem_cgroup *mem = NULL;
struct anon_vma *anon_vma = NULL;
@@ -638,7 +637,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
if (unlikely(split_huge_page(page)))
goto move_newpage;
- /* prepare cgroup just returns 0 or -ENOMEM */
+ /* mem_cgroup_prepare_migration never returns -EAGAIN */
rc = -EAGAIN;
if (!trylock_page(page)) {
@@ -662,8 +661,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
}
/* charge against new page */
- charge = mem_cgroup_prepare_migration(page, newpage, &mem);
- if (charge == -ENOMEM) {
+ if (mem_cgroup_prepare_migration(page, newpage, &mem)) {
rc = -ENOMEM;
goto unlock;
}
@@ -759,8 +757,7 @@ rcu_unlock:
if (rcu_locked)
rcu_read_unlock();
uncharge:
- if (!charge)
- mem_cgroup_end_migration(mem, page, newpage, rc == 0);
+ mem_cgroup_end_migration(mem, page, newpage, rc == 0);
unlock:
unlock_page(page);
--
1.7.0.4
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] memcg: remove unnecessary BUG_ON
2011-01-11 8:51 [PATCH 1/2] memcg: remove unnecessary BUG_ON Minchan Kim
2011-01-11 8:51 ` [PATCH 2/2] memcg: remove charge variable in unmap_and_move Minchan Kim
@ 2011-01-12 0:38 ` Daisuke Nishimura
2011-01-12 0:47 ` KAMEZAWA Hiroyuki
2 siblings, 0 replies; 6+ messages in thread
From: Daisuke Nishimura @ 2011-01-12 0:38 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, linux-mm, LKML, KAMEZAWA Hiroyuki, Balbir Singh,
Daisuke Nishimura
On Tue, 11 Jan 2011 17:51:11 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:
> Now memcg in unmap_and_move checks BUG_ON of charge.
> mem_cgroup_prepare_migration returns either 0 or -ENOMEM.
> If it returns -ENOMEM, it jumps out unlock without the check.
> If it returns 0, it can pass BUG_ON. So it's meaningless.
> Let's remove it.
>
> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] memcg: remove charge variable in unmap_and_move
2011-01-11 8:51 ` [PATCH 2/2] memcg: remove charge variable in unmap_and_move Minchan Kim
@ 2011-01-12 0:38 ` Daisuke Nishimura
2011-01-12 0:48 ` KAMEZAWA Hiroyuki
1 sibling, 0 replies; 6+ messages in thread
From: Daisuke Nishimura @ 2011-01-12 0:38 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, linux-mm, LKML, KAMEZAWA Hiroyuki, Balbir Singh,
Daisuke Nishimura
On Tue, 11 Jan 2011 17:51:12 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:
> memcg charge/uncharge could be handled by mem_cgroup_[prepare/end]
> migration itself so charge local variable in unmap_and_move lost the role
> since we introduced 01b1ae63c2.
>
> In addition, the variable name is not good like below.
>
> int unmap_and_move()
> {
> charge = mem_cgroup_prepare_migration(xxx);
> ..
> BUG_ON(charge); <-- BUG if it is charged?
> ..
> uncharge:
> if (!charge) <-- why do we have to uncharge !charge?
> mem_group_end_migration(xxx);
> ..
> }
>
> So let's remove unnecessary and confusing variable.
>
> Suggested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] memcg: remove unnecessary BUG_ON
2011-01-11 8:51 [PATCH 1/2] memcg: remove unnecessary BUG_ON Minchan Kim
2011-01-11 8:51 ` [PATCH 2/2] memcg: remove charge variable in unmap_and_move Minchan Kim
2011-01-12 0:38 ` [PATCH 1/2] memcg: remove unnecessary BUG_ON Daisuke Nishimura
@ 2011-01-12 0:47 ` KAMEZAWA Hiroyuki
2 siblings, 0 replies; 6+ messages in thread
From: KAMEZAWA Hiroyuki @ 2011-01-12 0:47 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, linux-mm, LKML, Balbir Singh, Daisuke Nishimura
On Tue, 11 Jan 2011 17:51:11 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:
> Now memcg in unmap_and_move checks BUG_ON of charge.
> mem_cgroup_prepare_migration returns either 0 or -ENOMEM.
> If it returns -ENOMEM, it jumps out unlock without the check.
> If it returns 0, it can pass BUG_ON. So it's meaningless.
> Let's remove it.
>
> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] memcg: remove charge variable in unmap_and_move
2011-01-11 8:51 ` [PATCH 2/2] memcg: remove charge variable in unmap_and_move Minchan Kim
2011-01-12 0:38 ` Daisuke Nishimura
@ 2011-01-12 0:48 ` KAMEZAWA Hiroyuki
1 sibling, 0 replies; 6+ messages in thread
From: KAMEZAWA Hiroyuki @ 2011-01-12 0:48 UTC (permalink / raw)
To: Minchan Kim
Cc: Andrew Morton, linux-mm, LKML, Balbir Singh, Daisuke Nishimura
On Tue, 11 Jan 2011 17:51:12 +0900
Minchan Kim <minchan.kim@gmail.com> wrote:
> memcg charge/uncharge could be handled by mem_cgroup_[prepare/end]
> migration itself so charge local variable in unmap_and_move lost the role
> since we introduced 01b1ae63c2.
>
> In addition, the variable name is not good like below.
>
> int unmap_and_move()
> {
> charge = mem_cgroup_prepare_migration(xxx);
> ..
> BUG_ON(charge); <-- BUG if it is charged?
> ..
> uncharge:
> if (!charge) <-- why do we have to uncharge !charge?
> mem_group_end_migration(xxx);
> ..
> }
>
> So let's remove unnecessary and confusing variable.
>
> Suggested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2011-01-12 0:54 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2011-01-11 8:51 [PATCH 1/2] memcg: remove unnecessary BUG_ON Minchan Kim
2011-01-11 8:51 ` [PATCH 2/2] memcg: remove charge variable in unmap_and_move Minchan Kim
2011-01-12 0:38 ` Daisuke Nishimura
2011-01-12 0:48 ` KAMEZAWA Hiroyuki
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