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SubjectRe: [PATCH v5 1/6] memg: better numa scanning
On Tue 09-08-11 19:08:24, KAMEZAWA Hiroyuki wrote:
>
> Making memcg numa's scanning information update by schedule_work().
>
> Now, memcg's numa information is updated under a thread doing
> memory reclaim. It's not very heavy weight now. But upcoming updates
> around numa scanning will add more works. This patch makes
> the update be done by schedule_work() and reduce latency caused
> by this updates.

I am not sure whether this pays off. Anyway, I think it would be better
to place this patch somewhere at the end of the series so that we can
measure its impact separately.

>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Otherwise looks good to me.
Reviewed-by: Michal Hocko <mhocko@suse.cz>

Just a minor nit bellow.

> ---
> mm/memcontrol.c | 42 ++++++++++++++++++++++++++++++------------
> 1 file changed, 30 insertions(+), 12 deletions(-)
>
> Index: mmotm-Aug3/mm/memcontrol.c
> ===================================================================
> --- mmotm-Aug3.orig/mm/memcontrol.c
> +++ mmotm-Aug3/mm/memcontrol.c
> @@ -285,6 +285,7 @@ struct mem_cgroup {
> nodemask_t scan_nodes;
> atomic_t numainfo_events;
> atomic_t numainfo_updating;
> + struct work_struct numainfo_update_work;
> #endif
> /*
> * Should the accounting and control be hierarchical, per subtree?
> @@ -1567,6 +1568,23 @@ static bool test_mem_cgroup_node_reclaim
> }
> #if MAX_NUMNODES > 1
>
> +static void mem_cgroup_numainfo_update_work(struct work_struct *work)
> +{
> + struct mem_cgroup *memcg;
> + int nid;
> +
> + memcg = container_of(work, struct mem_cgroup, numainfo_update_work);
> +
> + memcg->scan_nodes = node_states[N_HIGH_MEMORY];
> + for_each_node_mask(nid, node_states[N_HIGH_MEMORY]) {
> + if (!test_mem_cgroup_node_reclaimable(memcg, nid, false))
> + node_clear(nid, memcg->scan_nodes);
> + }
> + atomic_set(&memcg->numainfo_updating, 0);
> + css_put(&memcg->css);
> +}
> +
> +
> /*
> * Always updating the nodemask is not very good - even if we have an empty
> * list or the wrong list here, we can start from some node and traverse all
> @@ -1575,7 +1593,6 @@ static bool test_mem_cgroup_node_reclaim
> */

Would be good to update the function comment as well (we still have 10s
period there).

> static void mem_cgroup_may_update_nodemask(struct mem_cgroup *mem)
> {
> - int nid;
> /*
> * numainfo_events > 0 means there was at least NUMAINFO_EVENTS_TARGET
> * pagein/pageout changes since the last update.
[...]

--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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