Messages in this thread Patch in this message | | | Date | Thu, 15 Jan 2009 16:45:37 +0900 | From | Daisuke Nishimura <> | Subject | [RFC][PATCH] memcg: get/put parents at create/free |
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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); + } } +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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