Re: [RFC PATCH 5/6] hugetlbfs: Add controller support for private mapping

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

On Fri, 17 Feb 2012 13:22:44 +0800, bill4carson <bill4carson@gmail.com> wrote:
> 
> 
> On 2012年02月11日 05:36, Aneesh Kumar K.V wrote:
> > From: "Aneesh Kumar K.V"<aneesh.kumar@linux.vnet.ibm.com>
> >
> > HugeTLB controller is different from a memory controller in that we charge
> > controller during mmap() time and not fault time. This make sure userspace
> > can fallback to non-hugepage allocation when mmap fails due to controller
> > limit.
> >
> > For private mapping we always charge/uncharge from the current task cgroup.
> > Charging happens during mmap(2) and uncharge happens during the
> > vm_operations->close when resv_map refcount reaches zero. The uncharge count
> > is stored in struct resv_map. For child task after fork the charging happens
> > during fault time in alloc_huge_page. We also need to make sure for private
> > mapping each vma for hugeTLB mapping have struct resv_map allocated so that we
> > can store the uncharge count in resv_map.
> >
> > Signed-off-by: Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com>
> > ---
> >   fs/hugetlbfs/hugetlb_cgroup.c  |   50 ++++++++++++++++++++++++++++++++
> >   include/linux/hugetlb.h        |    7 ++++
> >   include/linux/hugetlb_cgroup.h |   16 ++++++++++
> >   mm/hugetlb.c                   |   62 ++++++++++++++++++++++++++++++++--------
> >   4 files changed, 123 insertions(+), 12 deletions(-)
> >
> > diff --git a/fs/hugetlbfs/hugetlb_cgroup.c b/fs/hugetlbfs/hugetlb_cgroup.c
> > index c478fb0..f828fb2 100644
> > --- a/fs/hugetlbfs/hugetlb_cgroup.c
> > +++ b/fs/hugetlbfs/hugetlb_cgroup.c
> > @@ -458,3 +458,53 @@ long  hugetlb_truncate_cgroup_charge(struct hstate *h,
> >   	}
> >   	return chg;
> >   }
> > +
> > +int hugetlb_priv_page_charge(struct resv_map *map, struct hstate *h, long chg)
> > +{
> > +	long csize;
> > +	int idx, ret;
> > +	struct hugetlb_cgroup *h_cg;
> > +	struct res_counter *fail_res;
> > +
> > +	/*
> > +	 * Get the task cgroup within rcu_readlock and also
> > +	 * get cgroup reference to make sure cgroup destroy won't
> > +	 * race with page_charge. We don't allow a cgroup destroy
> > +	 * when the cgroup have some charge against it
> > +	 */
> > +	rcu_read_lock();
> > +	h_cg = task_hugetlbcgroup(current);
> > +	css_get(&h_cg->css);
> > +	rcu_read_unlock();
> > +
> > +	if (hugetlb_cgroup_is_root(h_cg)) {
> > +		ret = chg;
> > +		goto err_out;
> > +	}
> > +
> > +	csize = chg * huge_page_size(h);
> > +	idx = h - hstates;
> > +	ret = res_counter_charge(&h_cg->memhuge[idx], csize,&fail_res);
> > +	if (!ret) {
> > +		map->nr_pages[idx] += chg<<  huge_page_order(h);
> > +		ret = chg;
> > +	}
> > +err_out:
> > +	css_put(&h_cg->css);
> > +	return ret;
> > +}
> > +
> > +void hugetlb_priv_page_uncharge(struct resv_map *map, int idx, int nr_pages)
> > +{
> > +	struct hugetlb_cgroup *h_cg;
> > +	unsigned long csize = nr_pages * PAGE_SIZE;
> > +
> > +	rcu_read_lock();
> > +	h_cg = task_hugetlbcgroup(current);
> > +	if (!hugetlb_cgroup_is_root(h_cg)) {
> > +		res_counter_uncharge(&h_cg->memhuge[idx], csize);
> > +		map->nr_pages[idx] -= nr_pages;
> > +	}
> > +	rcu_read_unlock();
> > +	return;
> > +}
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 4392b6a..e2ba381 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -233,6 +233,12 @@ struct hstate {
> >   	char name[HSTATE_NAME_LEN];
> >   };
> >
> > +struct resv_map {
> > +	struct kref refs;
> > +	int nr_pages[HUGE_MAX_HSTATE];
> > +	struct list_head regions;
> > +};
> > +
> 
> Please put resv_map after HUGE_MAX_HSTATE definition,
> otherwise it will break on non-x86 arches, which has no
> HUGE_MAX_HSTATE definition.
> 
> 
> #ifndef HUGE_MAX_HSTATE
> #define HUGE_MAX_HSTATE 1
> #endif
> 
> +struct resv_map {
> +	struct kref refs;
> +	int nr_pages[HUGE_MAX_HSTATE];
> +	struct list_head regions;
> +};
> 
> 
> 
> 

Will do in the next iteration.

Thanks for the review
-aneesh

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