Messages in this thread Patch in this message | | | Date | Thu, 15 Jan 2009 11:14:20 +0900 | From | Daisuke Nishimura <> | Subject | Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete |
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> > > 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 Check if the memcg is obsolete by css_tryget, and don't call 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); } }
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