lkml.org 
[lkml]   [2009]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete
> > > To handle the problem "parent may be obsolete",
> > >
> > > call mem_cgroup_get(parent) at create()
> > > call mem_cgroup_put(parent) at freeing memcg.
> > > (regardless of use_hierarchy.)
> > >
> > > is clearer way to go, I think.
> > >
> > > I wonder whether there is mis-accounting problem or not..
> > >
> > > So, adding css_tryget() around problematic code can be a fix.
> > > --
> > > mem = swap_cgroup_record();
> > > if (css_tryget(&mem->css)) {
> > > res_counter_uncharge(&mem->memsw, PAZE_SIZE);
> > > css_put(&mem->css)
> > > }
> > > --
> > > I like css_tryget() rather than mem_cgroup_obsolete().
> > I agree.
> > The updated version is attached.
> >
> >
> > Thanks,
> > Daisuke nishimura.
> >
> > > To be honest, I'd like to remove memcg special stuff when I can.
> > >
> > > Thanks,
> > > -Kame
> > >
> > ===
> > From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> >
> > mem_cgroup_get ensures that the memcg that has been got can be accessed
> > even after the directory has been removed, but it doesn't ensure that parents
> > of it can be accessed: parents might have been freed already by rmdir.
> >
> > This causes a bug in case of use_hierarchy==1, because res_counter_uncharge
> > climb up the tree.
> >
> > Check if the memcg is obsolete by css_tryget, and don't call
> > res_counter_uncharge when obsole.
> >
> > Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> seems nice loock.
>
>
> > ---
> > mm/memcontrol.c | 15 ++++++++++++---
> > 1 files changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index fb62b43..4e3b100 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1182,7 +1182,10 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
> > /* avoid double counting */
> > mem = swap_cgroup_record(ent, NULL);
> > if (mem) {
> > - res_counter_uncharge(&mem->memsw, PAGE_SIZE);
> > + if (!css_tryget(&mem->css)) {
> > + res_counter_uncharge(&mem->memsw, PAGE_SIZE);
> > + css_put(&mem->css);
> > + }
> > mem_cgroup_put(mem);
> > }
> > }
>
> I think css_tryget() returns "ture" at success....
>
> So,
> ==
> if (mem && css_tryget(&mem->css))
> res_counter....
>
> is correct.
>
> -Kame
>
Ooops! you are right.
Sorry for my silly mistake..

"mem" is checked beforehand, so I think css_tryget would be enough.
I'm now testing the attached one.


Thanks,
Daisuke Nishimura.
===
From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

mem_cgroup_get ensures that the memcg that has been got can be accessed
even after the directory has been removed, but it doesn't ensure that parents
of it can be accessed: parents might have been freed already by rmdir.

This causes a bug in case of use_hierarchy==1, because res_counter_uncharge
climb up the tree.

Check if the memcg is obsolete by css_tryget, and don't call
res_counter_uncharge when obsole.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
---
mm/memcontrol.c | 15 ++++++++++++---
1 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fb62b43..b9d5271 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1182,7 +1182,10 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
/* avoid double counting */
mem = swap_cgroup_record(ent, NULL);
if (mem) {
- res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+ if (css_tryget(&mem->css)) {
+ res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+ css_put(&mem->css);
+ }
mem_cgroup_put(mem);
}
}
@@ -1252,7 +1255,10 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
struct mem_cgroup *memcg;
memcg = swap_cgroup_record(ent, NULL);
if (memcg) {
- res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+ if (css_tryget(&memcg->css)) {
+ res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+ css_put(&memcg->css);
+ }
mem_cgroup_put(memcg);
}

@@ -1397,7 +1403,10 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)

memcg = swap_cgroup_record(ent, NULL);
if (memcg) {
- res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+ if (css_tryget(&memcg->css)) {
+ res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+ css_put(&memcg->css);
+ }
mem_cgroup_put(memcg);
}
}

\
 
 \ /
  Last update: 2009-01-15 03:33    [W:0.089 / U:4.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site