Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> writes:
> (2012/06/09 17:59), Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V"<aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>>
>> This patchset add the charge and uncharge routines for hugetlb cgroup.
>> This will be used in later patches when we allocate/free HugeTLB
>> pages.
>>
>> Signed-off-by: Aneesh Kumar K.V<aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>
>
> I'm sorry if following has been already pointed out.
>
>> ---
>> mm/hugetlb_cgroup.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 87 insertions(+)
>>
>> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
>> index 20a32c5..48efd5a 100644
>> --- a/mm/hugetlb_cgroup.c
>> +++ b/mm/hugetlb_cgroup.c
>> @@ -105,6 +105,93 @@ static int hugetlb_cgroup_pre_destroy(struct cgroup *cgroup)
>> return -EBUSY;
>> }
>>
>> +int hugetlb_cgroup_charge_page(int idx, unsigned long nr_pages,
>> + struct hugetlb_cgroup **ptr)
>> +{
>> + int ret = 0;
>> + struct res_counter *fail_res;
>> + struct hugetlb_cgroup *h_cg = NULL;
>> + unsigned long csize = nr_pages * PAGE_SIZE;
>> +
>> + if (hugetlb_cgroup_disabled())
>> + goto done;
>> + /*
>> + * We don't charge any cgroup if the compound page have less
>> + * than 3 pages.
>> + */
>> + if (hstates[idx].order< 2)
>> + goto done;
>> +again:
>> + rcu_read_lock();
>> + h_cg = hugetlb_cgroup_from_task(current);
>> + if (!h_cg)
>> + h_cg = root_h_cgroup;
>> +
>> + if (!css_tryget(&h_cg->css)) {
>> + rcu_read_unlock();
>> + goto again;
>> + }
>> + rcu_read_unlock();
>> +
>> + ret = res_counter_charge(&h_cg->hugepage[idx], csize,&fail_res);
>> + css_put(&h_cg->css);
>> +done:
>> + *ptr = h_cg;
>> + return ret;
>> +}
>> +
>
> Memory cgroup uses very complicated 'charge' routine for handling pageout...
> which gets sleep.
>
> For hugetlbfs, it has not sleep routine, you can do charge in simple way.
> I guess...get/put here is overkill.
>
> For example, h_cg cannot be freed while it has tasks. So, if 'current' is
> belongs to the cgroup, it cannot be disappear. Then, you don't need get/put,
> additional atomic ops for holding cgroup.
>
> rcu_read_lock();
> h_cg = hugetlb_cgroup_from_task(current);
> ret = res_counter_charge(&h_cg->hugetpage[idx], csize, &fail_res);
> rcu_read_unlock();
>
> return ret;
>
What if the task got moved ot of the cgroup and cgroup got deleted by an
rmdir ?
-aneesh
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