On Fri 10-06-11 18:59:52, KAMEZAWA Hiroyuki wrote:
> On Fri, 10 Jun 2011 11:08:02 +0200
> Michal Hocko <mhocko@xxxxxxx> wrote:
>
> > On Fri 10-06-11 17:39:58, KAMEZAWA Hiroyuki wrote:
> > > On Fri, 10 Jun 2011 10:12:19 +0200
> > > Michal Hocko <mhocko@xxxxxxx> wrote:
> > >
> > > > On Thu 09-06-11 09:30:45, KAMEZAWA Hiroyuki wrote:
> > [...]
> > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > > > > index bd9052a..3baddcb 100644
> > > > > --- a/mm/memcontrol.c
> > > > > +++ b/mm/memcontrol.c
> > > > [...]
> > > > > static struct mem_cgroup_per_zone *
> > > > > mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
> > > > > @@ -1670,8 +1670,6 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> > > > > victim = mem_cgroup_select_victim(root_mem);
> > > > > if (victim == root_mem) {
> > > > > loop++;
> > > > > - if (loop >= 1)
> > > > > - drain_all_stock_async();
> > > > > if (loop >= 2) {
> > > > > /*
> > > > > * If we have not been able to reclaim
> > > > > @@ -1723,6 +1721,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> > > > > return total;
> > > > > } else if (mem_cgroup_margin(root_mem))
> > > > > return total;
> > > > > + drain_all_stock_async(root_mem);
> > > > > }
> > > > > return total;
> > > > > }
> > > >
> > > > I still think that we pointlessly reclaim even though we could have a
> > > > lot of pages pre-charged in the cache (the more CPUs we have the more
> > > > significant this might be).
> > >
> > > The more CPUs, the more scan cost for each per-cpu memory, which makes
> > > cache-miss.
> > >
> > > I know placement of drain_all_stock_async() is not big problem on my host,
> > > which has 2socket/8core cpus. But, assuming 1000+ cpu host,
> >
> > Hmm, it really depends what you want to optimize for. Reclaim path is
> > already slow path and cache misses, while not good, are not the most
> > significant issue, I guess.
> > What I would see as a much bigger problem is that there might be a lot
> > of memory pre-charged at those per-cpu caches. Falling into a reclaim
> > costs us much more IMO and we can evict something that could be useful
> > for no good reason.
> >
>
> It's waste of time to talk this kind of things without the numbers.
>
> ok, I don't change the caller's logic. Discuss this when someone gets
> number of LARGE smp box.
Sounds reasonable.
[..,]
> please test/ack if ok.
see comment bellow.
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
[...]
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index bd9052a..75713cb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -359,7 +359,7 @@ enum charge_type {
> static void mem_cgroup_get(struct mem_cgroup *mem);
> static void mem_cgroup_put(struct mem_cgroup *mem);
> static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
> -static void drain_all_stock_async(void);
> +static void drain_all_stock_async(struct mem_cgroup *mem);
>
> static struct mem_cgroup_per_zone *
> mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
> @@ -1670,8 +1670,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
> victim = mem_cgroup_select_victim(root_mem);
> if (victim == root_mem) {
> loop++;
> - if (loop >= 1)
> - drain_all_stock_async();
> + drain_all_stock_async(root_mem);
> if (loop >= 2) {
> /*
> * If we have not been able to reclaim
This still doesn't prevent from direct reclaim even though we have freed
enough pages from pcp caches. Should I post it as a separate patch?
> @@ -1934,9 +1933,12 @@ struct memcg_stock_pcp {
> struct mem_cgroup *cached; /* this never be root cgroup */
> unsigned int nr_pages;
> struct work_struct work;
> + unsigned long flags;
> +#define ASYNC_FLUSHING (0)
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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