On Tue, 05 Oct 2010 12:00:17 -0700
Greg Thelen <gthelen@xxxxxxxxxx> wrote:
> Andrea Righi <arighi@xxxxxxxxxxx> writes:
>
> > On Sun, Oct 03, 2010 at 11:58:02PM -0700, Greg Thelen wrote:
> >> Extend mem_cgroup to contain dirty page limits. Also add routines
> >> allowing the kernel to query the dirty usage of a memcg.
> >>
> >> These interfaces not used by the kernel yet. A subsequent commit
> >> will add kernel calls to utilize these new routines.
> >
> > A small note below.
> >
> >>
> >> Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
> >> Signed-off-by: Andrea Righi <arighi@xxxxxxxxxxx>
> >> ---
> >> include/linux/memcontrol.h | 44 +++++++++++
> >> mm/memcontrol.c | 180 +++++++++++++++++++++++++++++++++++++++++++-
> >> 2 files changed, 223 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> >> index 6303da1..dc8952d 100644
> >> --- a/include/linux/memcontrol.h
> >> +++ b/include/linux/memcontrol.h
> >> @@ -19,6 +19,7 @@
> >>
> >> #ifndef _LINUX_MEMCONTROL_H
> >> #define _LINUX_MEMCONTROL_H
> >> +#include <linux/writeback.h>
> >> #include <linux/cgroup.h>
> >> struct mem_cgroup;
> >> struct page_cgroup;
> >> @@ -33,6 +34,30 @@ enum mem_cgroup_write_page_stat_item {
> >> MEMCG_NR_FILE_UNSTABLE_NFS, /* # of NFS unstable pages */
> >> };
> >>
> >> +/* Cgroup memory statistics items exported to the kernel */
> >> +enum mem_cgroup_read_page_stat_item {
> >> + MEMCG_NR_DIRTYABLE_PAGES,
> >> + MEMCG_NR_RECLAIM_PAGES,
> >> + MEMCG_NR_WRITEBACK,
> >> + MEMCG_NR_DIRTY_WRITEBACK_PAGES,
> >> +};
> >> +
> >> +/* Dirty memory parameters */
> >> +struct vm_dirty_param {
> >> + int dirty_ratio;
> >> + int dirty_background_ratio;
> >> + unsigned long dirty_bytes;
> >> + unsigned long dirty_background_bytes;
> >> +};
> >> +
> >> +static inline void get_global_vm_dirty_param(struct vm_dirty_param *param)
> >> +{
> >> + param->dirty_ratio = vm_dirty_ratio;
> >> + param->dirty_bytes = vm_dirty_bytes;
> >> + param->dirty_background_ratio = dirty_background_ratio;
> >> + param->dirty_background_bytes = dirty_background_bytes;
> >> +}
> >> +
> >> extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
> >> struct list_head *dst,
> >> unsigned long *scanned, int order,
> >> @@ -145,6 +170,10 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
> >> mem_cgroup_update_page_stat(page, idx, -1);
> >> }
> >>
> >> +bool mem_cgroup_has_dirty_limit(void);
> >> +void get_vm_dirty_param(struct vm_dirty_param *param);
> >> +s64 mem_cgroup_page_stat(enum mem_cgroup_read_page_stat_item item);
> >> +
> >> unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> >> gfp_t gfp_mask);
> >> u64 mem_cgroup_get_limit(struct mem_cgroup *mem);
> >> @@ -326,6 +355,21 @@ static inline void mem_cgroup_dec_page_stat(struct page *page,
> >> {
> >> }
> >>
> >> +static inline bool mem_cgroup_has_dirty_limit(void)
> >> +{
> >> + return false;
> >> +}
> >> +
> >> +static inline void get_vm_dirty_param(struct vm_dirty_param *param)
> >> +{
> >> + get_global_vm_dirty_param(param);
> >> +}
> >> +
> >> +static inline s64 mem_cgroup_page_stat(enum mem_cgroup_read_page_stat_item item)
> >> +{
> >> + return -ENOSYS;
> >> +}
> >> +
> >> static inline
> >> unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> >> gfp_t gfp_mask)
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index f40839f..6ec2625 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -233,6 +233,10 @@ struct mem_cgroup {
> >> atomic_t refcnt;
> >>
> >> unsigned int swappiness;
> >> +
> >> + /* control memory cgroup dirty pages */
> >> + struct vm_dirty_param dirty_param;
> >> +
> >> /* OOM-Killer disable */
> >> int oom_kill_disable;
> >>
> >> @@ -1132,6 +1136,172 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
> >> return swappiness;
> >> }
> >>
> >> +/*
> >> + * Returns a snapshot of the current dirty limits which is not synchronized with
> >> + * the routines that change the dirty limits. If this routine races with an
> >> + * update to the dirty bytes/ratio value, then the caller must handle the case
> >> + * where both dirty_[background_]_ratio and _bytes are set.
> >> + */
> >> +static void __mem_cgroup_get_dirty_param(struct vm_dirty_param *param,
> >> + struct mem_cgroup *mem)
> >> +{
> >> + if (mem && !mem_cgroup_is_root(mem)) {
> >> + param->dirty_ratio = mem->dirty_param.dirty_ratio;
> >> + param->dirty_bytes = mem->dirty_param.dirty_bytes;
> >> + param->dirty_background_ratio =
> >> + mem->dirty_param.dirty_background_ratio;
> >> + param->dirty_background_bytes =
> >> + mem->dirty_param.dirty_background_bytes;
> >> + } else {
> >> + get_global_vm_dirty_param(param);
> >> + }
> >> +}
> >> +
> >> +/*
> >> + * Get dirty memory parameters of the current memcg or global values (if memory
> >> + * cgroups are disabled or querying the root cgroup).
> >> + */
> >> +void get_vm_dirty_param(struct vm_dirty_param *param)
> >> +{
> >> + struct mem_cgroup *memcg;
> >> +
> >> + if (mem_cgroup_disabled()) {
> >> + get_global_vm_dirty_param(param);
> >> + return;
> >> + }
> >> +
> >> + /*
> >> + * It's possible that "current" may be moved to other cgroup while we
> >> + * access cgroup. But precise check is meaningless because the task can
> >> + * be moved after our access and writeback tends to take long time. At
> >> + * least, "memcg" will not be freed under rcu_read_lock().
> >> + */
> >> + rcu_read_lock();
> >> + memcg = mem_cgroup_from_task(current);
> >> + __mem_cgroup_get_dirty_param(param, memcg);
> >> + rcu_read_unlock();
> >> +}
> >> +
> >> +/*
> >> + * Check if current memcg has local dirty limits. Return true if the current
> >> + * memory cgroup has local dirty memory settings.
> >> + */
> >> +bool mem_cgroup_has_dirty_limit(void)
> >> +{
> >> + struct mem_cgroup *mem;
> >> +
> >> + if (mem_cgroup_disabled())
> >> + return false;
> >> +
> >> + mem = mem_cgroup_from_task(current);
> >> + return mem && !mem_cgroup_is_root(mem);
> >> +}
> >
> > We only check the pointer without dereferencing it, so this is probably
> > ok, but maybe this is safer:
> >
> > bool mem_cgroup_has_dirty_limit(void)
> > {
> > struct mem_cgroup *mem;
> > bool ret;
> >
> > if (mem_cgroup_disabled())
> > return false;
> >
> > rcu_read_lock();
> > mem = mem_cgroup_from_task(current);
> > ret = mem && !mem_cgroup_is_root(mem);
> > rcu_read_unlock();
> >
> > return ret;
> > }
> >
> > rcu_read_lock() should be held in mem_cgroup_from_task(), otherwise
> > lockdep could detect this as an error.
> >
> > Thanks,
> > -Andrea
>
> Good suggestion. I agree that lockdep might catch this. There are some
> unrelated debug_locks failures (even without my patches) that I worked
> around to get lockdep to complain about this one. I applied your
> suggested fix and lockdep was happy. I will incorporate this fix into
> the next revision of the patch series.
>
Hmm, considering other parts, shouldn't we define mem_cgroup_from_task
as macro ?
Thanks,
-Kame
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>