Messages in this thread | | | Date | Thu, 15 Jan 2009 16:54:53 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFC][PATCH] memcg: get/put parents at create/free |
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On Thu, 15 Jan 2009 16:45:37 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> On Thu, 15 Jan 2009 13:38:14 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > > On Thu, 15 Jan 2009 11:14:20 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > > > > > > 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.. > > > > > > > > hmm, after more consideration, although this patch can prevent the BUG, > > it can leak memsw accounting of parents because memsw of parents, which > > have been incremented by charge, does not decremented. > > > > I'll try pet/put parent approach.. > > Or any other good ideas ? > > > I attach a tryial patch. > > It has been working fine so far(for about 1 hour). > > 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. > > This patch tries to fix this probrem by getting parents at create, and > putting them at freeing. > > Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> > --- > mm/memcontrol.c | 33 ++++++++++++++++++++++++++++++++- > 1 files changed, 32 insertions(+), 1 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fb62b43..b4aed07 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -202,6 +202,8 @@ pcg_default_flags[NR_CHARGE_TYPE] = { > > static void mem_cgroup_get(struct mem_cgroup *mem); > static void mem_cgroup_put(struct mem_cgroup *mem); > +static void mem_cgroup_get_parents(struct mem_cgroup *mem); > +static void mem_cgroup_put_parents(struct mem_cgroup *mem); > > static void mem_cgroup_charge_statistics(struct mem_cgroup *mem, > struct page_cgroup *pc, > @@ -2185,10 +2187,38 @@ static void mem_cgroup_get(struct mem_cgroup *mem) > > static void mem_cgroup_put(struct mem_cgroup *mem) > { > - if (atomic_dec_and_test(&mem->refcnt)) > + if (atomic_dec_and_test(&mem->refcnt)) { > + mem_cgroup_put_parents(mem); > __mem_cgroup_free(mem); > + } > +} > + > +static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) > +{ > + if (!mem->res.parent) > + return NULL; > + return mem_cgroup_from_res_counter(mem->res.parent, res); > +} > + > +static void mem_cgroup_get_parents(struct mem_cgroup *mem) > +{ > + struct mem_cgroup *parent = parent_mem_cgroup(mem); > + > + while (parent) { > + mem_cgroup_get(parent); > + parent = parent_mem_cgroup(parent); > + } > } >
does we have to add refcnt to all ancestors ?
Thanks, -Kame
> +static void mem_cgroup_put_parents(struct mem_cgroup *mem) > +{ > + struct mem_cgroup *parent = parent_mem_cgroup(mem); > + > + while (parent) { > + mem_cgroup_put(parent); > + parent = parent_mem_cgroup(parent); > + } > +} > > #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP > static void __init enable_swap_cgroup(void) > @@ -2237,6 +2267,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) > if (parent) > mem->swappiness = get_swappiness(parent); > atomic_set(&mem->refcnt, 1); > + mem_cgroup_get_parents(mem); > return &mem->css; > free_out: > __mem_cgroup_free(mem); >
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