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Message-ID: <20120328154434.GN20949@tiehlicka.suse.cz>
Date: Wed, 28 Mar 2012 17:44:34 +0200
From: Michal Hocko <mhocko@...e.cz>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc: linux-mm@...ck.org, mgorman@...e.de,
kamezawa.hiroyu@...fujitsu.com, dhillf@...il.com,
aarcange@...hat.com, akpm@...ux-foundation.org, hannes@...xchg.org,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH -V4 04/10] memcg: Add HugeTLB extension
On Wed 28-03-12 19:10:36, Aneesh Kumar K.V wrote:
> Michal Hocko <mhocko@...e.cz> writes:
>
> > On Fri 16-03-12 23:09:24, Aneesh Kumar K.V wrote:
> >> From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
> >>
> >> This patch implements a memcg extension that allows us to control
> >> HugeTLB allocations via memory controller.
> >
> > And the infrastructure is not used at this stage (you forgot to
> > mention).
> > The changelog should be much more descriptive.
>
>
> Will update the changelog.
Thx
>
> >
> >>
> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> >> ---
> >> include/linux/hugetlb.h | 1 +
> >> include/linux/memcontrol.h | 42 +++++++++++++
> >> init/Kconfig | 8 +++
> >> mm/hugetlb.c | 2 +-
> >> mm/memcontrol.c | 138 ++++++++++++++++++++++++++++++++++++++++++++
> >> 5 files changed, 190 insertions(+), 1 deletions(-)
> >>
> > [...]
> >> diff --git a/init/Kconfig b/init/Kconfig
> >> index 3f42cd6..f0eb8aa 100644
> >> --- a/init/Kconfig
> >> +++ b/init/Kconfig
> >> @@ -725,6 +725,14 @@ config CGROUP_PERF
> >>
> >> Say N if unsure.
> >>
> >> +config MEM_RES_CTLR_HUGETLB
> >> + bool "Memory Resource Controller HugeTLB Extension (EXPERIMENTAL)"
> >> + depends on CGROUP_MEM_RES_CTLR && HUGETLB_PAGE && EXPERIMENTAL
> >> + default n
> >> + help
> >> + Add HugeTLB management to memory resource controller. When you
> >> + enable this, you can put a per cgroup limit on HugeTLB usage.
> >
> > How does it interact with the hard/soft limists etc...
>
>
> There is no softlimit support for HugeTLB extension.
Sure, sorry for not being precise. The point was how this interacts with
memcg hard/soft limit (they are independent) etc...
> > [...]
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 6728a7a..4b36c5e 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -235,6 +235,10 @@ struct mem_cgroup {
> >> */
> >> struct res_counter memsw;
> >> /*
> >> + * the counter to account for hugepages from hugetlb.
> >> + */
> >> + struct res_counter hugepage[HUGE_MAX_HSTATE];
> >> + /*
> >> * Per cgroup active and inactive list, similar to the
> >> * per zone LRU lists.
> >> */
> >> @@ -3156,6 +3160,128 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
> >> }
> >> #endif
> >>
> >> +#ifdef CONFIG_MEM_RES_CTLR_HUGETLB
> >> +static bool mem_cgroup_have_hugetlb_usage(struct mem_cgroup *memcg)
> >> +{
> >> + int idx;
> >> + for (idx = 0; idx < hugetlb_max_hstate; idx++) {
> >
> > Maybe we should expose for_each_hstate as well...
>
>
> That will not really help here. If we use for_each_hstate then we will
> need to use hstate_index to get the index.
Fair enough
> >> + if (memcg->hugepage[idx].usage > 0)
> >> + return 1;
> >> + }
> >> + return 0;
> >> +}
> >> +
> >> +int mem_cgroup_hugetlb_charge_page(int idx, unsigned long nr_pages,
> >> + struct mem_cgroup **ptr)
> >> +{
> >> + int ret = 0;
> >> + struct mem_cgroup *memcg;
> >> + struct res_counter *fail_res;
> >> + unsigned long csize = nr_pages * PAGE_SIZE;
> >> +
> >> + if (mem_cgroup_disabled())
> >> + return 0;
> >> +again:
> >> + rcu_read_lock();
> >> + memcg = mem_cgroup_from_task(current);
> >> + if (!memcg)
> >> + memcg = root_mem_cgroup;
> >> + if (mem_cgroup_is_root(memcg)) {
> >> + rcu_read_unlock();
> >> + goto done;
> >> + }
> >> + if (!css_tryget(&memcg->css)) {
> >> + rcu_read_unlock();
> >> + goto again;
> >> + }
> >> + rcu_read_unlock();
> >> +
> >> + ret = res_counter_charge(&memcg->hugepage[idx], csize, &fail_res);
> >> + css_put(&memcg->css);
> >> +done:
> >> + *ptr = memcg;
> >
> > Why do we set ptr even for the failure case after we dropped a
> > reference?
>
> That ensures that *ptr is NULL.
Does it? AFAICS res_counter_charge might fail and you would use non NULL
memcg (with a dropped reference).
[...]
> >> + SetPageCgroupUsed(pc);
> >> +
> >> + unlock_page_cgroup(pc);
> >> + return;
> >> +}
> >> +
> > [...]
> >> @@ -4887,6 +5013,7 @@ err_cleanup:
> >> static struct cgroup_subsys_state * __ref
> >> mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
> >> {
> >> + int idx;
> >> struct mem_cgroup *memcg, *parent;
> >> long error = -ENOMEM;
> >> int node;
> >> @@ -4929,9 +5056,14 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
> >> * mem_cgroup(see mem_cgroup_put).
> >> */
> >> mem_cgroup_get(parent);
> >> + for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
> >
> > Do we have to init all hstates or is hugetlb_max_hstate enough?
>
>
> Yes. we do call mem_cgroup_create for root cgroup before initialzing
> hugetlb hstate.
drop a comment?
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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