Messages in this thread | | | Date | Sun, 11 Mar 2012 14:49:52 +0400 | From | Glauber Costa <> | Subject | Re: [PATCH v2 04/13] memcg: Make it possible to use the stock for more than one page. |
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On 03/10/2012 12:39 AM, Suleiman Souhlal wrote: > Signed-off-by: Suleiman Souhlal<suleiman@google.com> > --- > mm/memcontrol.c | 18 +++++++++--------- > 1 files changed, 9 insertions(+), 9 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 6fbb438..f605100 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1965,19 +1965,19 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock); > static DEFINE_MUTEX(percpu_charge_mutex); > > /* > - * Try to consume stocked charge on this cpu. If success, one page is consumed > - * from local stock and true is returned. If the stock is 0 or charges from a > - * cgroup which is not current target, returns false. This stock will be > - * refilled. > + * Try to consume stocked charge on this cpu. If success, nr_pages pages are > + * consumed from local stock and true is returned. If the stock is 0 or > + * charges from a cgroup which is not current target, returns false. > + * This stock will be refilled. > */ > -static bool consume_stock(struct mem_cgroup *memcg) > +static bool consume_stock(struct mem_cgroup *memcg, int nr_pages) > { > struct memcg_stock_pcp *stock; > bool ret = true; > > stock =&get_cpu_var(memcg_stock); > - if (memcg == stock->cached&& stock->nr_pages) > - stock->nr_pages--; > + if (memcg == stock->cached&& stock->nr_pages>= nr_pages) > + stock->nr_pages -= nr_pages; > else /* need to call res_counter_charge */ > ret = false; > put_cpu_var(memcg_stock); > @@ -2290,7 +2290,7 @@ again: > VM_BUG_ON(css_is_removed(&memcg->css)); > if (mem_cgroup_is_root(memcg)) > goto done; > - if (nr_pages == 1&& consume_stock(memcg)) > + if (consume_stock(memcg, nr_pages)) > goto done; > css_get(&memcg->css); > } else { > @@ -2315,7 +2315,7 @@ again: > rcu_read_unlock(); > goto done; > } > - if (nr_pages == 1&& consume_stock(memcg)) { > + if (consume_stock(memcg, nr_pages)) { > /* > * It seems dagerous to access memcg without css_get(). > * But considering how consume_stok works, it's not
This patch itself is fine in what it wants to achieve. But it made me think:
We'll jump into the stock code which makes user allocation faster. but we're not getting the benefit of it when we're accounting kmem. since we're allocating to both res_counters, we're actually defeating it altogether, since we now have to go to the global poll *everytime* (for memcg->kmem).
It would make a whole lot more sense to have the stock code moved to the res_counter. We're now starting to have more users of that anyway, so a common implementation makes sense.
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