linux-kernel - [PATCH] mark_page_accessed() in do_swap_page() move latter than memcg charge

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Date:	Thu, 15 Jan 2009 20:08:36 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com, balbir@...ux.vnet.ibm.com,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	lizf@...fujitsu.com, menage@...gle.com,
	Hugh Dickins <hugh@...itas.com>
Subject: [PATCH] mark_page_accessed() in do_swap_page() move latter than memcg charge


sorry for late responce.

> > In this case we've hit a case where the page is valid and the pc is
> > not. This does fix the problem, but won't this impact us getting
> > correct reclaim stats and thus indirectly impact the working of
> > pressure?
> > 
>  - If retruns NULL, only global LRU's status is updated. 
> 
> Because this page is not belongs to any memcg, we cannot update
> any counters. But yes, your point is a concern.
> 
> Maybe moving acitvate_page() to
> ==
> do_swap_page()
> {
>     
> - activate_page()
>    mem_cgroup_try_charge()..
>    ....
>    mem_cgroup_commit_charge()....
>    ....
> +  activate_page()   
> }
> ==
> is necessary. How do you think, kosaki ?


OK. it makes sense. and my test found no bug.

==

mark_page_accessed() update reclaim_stat statics.
but currently, memcg charge is called after mark_page_accessed().

then, mark_page_accessed() don't update memcg statics correctly.

fixing here.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>

---
 mm/memory.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: b/mm/memory.c
===================================================================
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2426,8 +2426,6 @@ static int do_swap_page(struct mm_struct
 		count_vm_event(PGMAJFAULT);
 	}
 
-	mark_page_accessed(page);
-
 	lock_page(page);
 	delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
 
@@ -2480,6 +2478,8 @@ static int do_swap_page(struct mm_struct
 		try_to_free_swap(page);
 	unlock_page(page);
 
+	mark_page_accessed(page);
+
 	if (write_access) {
 		ret |= do_wp_page(mm, vma, address, page_table, pmd, ptl, pte);
 		if (ret & VM_FAULT_ERROR)



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