Re: [BUGFIX][PATCH 3/4] mecg: fix oom flag at THP charge

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 28 Jan 2011 09:02:13 +0100
Johannes Weiner <hannes@cmpxchg.org> wrote:

> On Fri, Jan 28, 2011 at 12:27:29PM +0900, KAMEZAWA Hiroyuki wrote:
> > 
> > Thanks to Johanns and Daisuke for suggestion.
> > =
> > Hugepage allocation shouldn't trigger oom.
> > Allocation failure is not fatal.
> > 
> > Orignal-patch-by: Johannes Weiner <hannes@cmpxchg.org>
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > ---
> >  mm/memcontrol.c |    4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > Index: mmotm-0125/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0125.orig/mm/memcontrol.c
> > +++ mmotm-0125/mm/memcontrol.c
> > @@ -2369,11 +2369,14 @@ static int mem_cgroup_charge_common(stru
> >  	struct page_cgroup *pc;
> >  	int ret;
> >  	int page_size = PAGE_SIZE;
> > +	bool oom;
> >  
> >  	if (PageTransHuge(page)) {
> >  		page_size <<= compound_order(page);
> >  		VM_BUG_ON(!PageTransHuge(page));
> > -	}
> > +		oom = false;
> > +	} else
> > +		oom = true;
> 
> That needs a comment.  You can take the one from my patch if you like.
> 

How about this ?
==
Hugepage allocation shouldn't trigger oom.
Allocation failure is not fatal.

Changelog:
 - added comments.

Orignal-patch-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Index: mmotm-0125/mm/memcontrol.c
===================================================================
--- mmotm-0125.orig/mm/memcontrol.c
+++ mmotm-0125/mm/memcontrol.c
@@ -2366,11 +2366,18 @@ static int mem_cgroup_charge_common(stru
 	struct page_cgroup *pc;
 	int ret;
 	int page_size = PAGE_SIZE;
+	bool oom;
 
 	if (PageTransHuge(page)) {
 		page_size <<= compound_order(page);
 		VM_BUG_ON(!PageTransHuge(page));
-	}
+		/*
+		 * Hugepage allocation will retry in small pages even if
+		 * this allocation fails.
+		 */
+		oom = false;
+	} else
+		oom = true;
 
 	pc = lookup_page_cgroup(page);
 	/* can happen at boot */
@@ -2378,7 +2385,7 @@ static int mem_cgroup_charge_common(stru
 		return 0;
 	prefetchw(pc);
 
-	ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true, page_size);
+	ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, oom, page_size);
 	if (ret || !mem)
 		return ret;