From: Michal Hocko <mho...@suse.cz> __mem_cgroup_try_charge duplicates get_mem_cgroup_from_mm for charges which came without a memcg. The only reason seems to be a tiny optimization when css_tryget is not called if the charge can be consumed from the stock. Nevertheless css_tryget is very cheap since it has been reworked to use per-cpu counting so this optimization doesn't give us anything these days.
So let's drop the code duplication so that the code is more readable. Signed-off-by: Michal Hocko <mho...@suse.cz> Signed-off-by: Johannes Weiner <han...@cmpxchg.org> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> https://jira.sw.ru/browse/PSBM-51558 (cherry picked from commit b6b6cc72bc404c952968530d7df4c3a4ab82b65b) Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com> --- mm/memcontrol.c | 50 ++++++-------------------------------------------- 1 file changed, 6 insertions(+), 44 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 40ac81b..d6413c5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2873,52 +2873,14 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, again: if (*ptr) { /* css should be a valid one */ memcg = *ptr; - if (mem_cgroup_is_root(memcg)) - goto done; - if (consume_stock(memcg, nr_pages)) - goto done; css_get(&memcg->css); } else { - struct task_struct *p; - - rcu_read_lock(); - p = rcu_dereference(mm->owner); - /* - * Because we don't have task_lock(), "p" can exit. - * In that case, "memcg" can point to root or p can be NULL with - * race with swapoff. Then, we have small risk of mis-accouning. - * But such kind of mis-account by race always happens because - * we don't have cgroup_mutex(). It's overkill and we allo that - * small race, here. - * (*) swapoff at el will charge against mm-struct not against - * task-struct. So, mm->owner can be NULL. - */ - memcg = mem_cgroup_from_task(p); - if (!memcg) - memcg = root_mem_cgroup; - if (mem_cgroup_is_root(memcg)) { - rcu_read_unlock(); - goto done; - } - if (consume_stock(memcg, nr_pages)) { - /* - * It seems dagerous to access memcg without css_get(). - * But considering how consume_stok works, it's not - * necessary. If consume_stock success, some charges - * from this memcg are cached on this cpu. So, we - * don't need to call css_get()/css_tryget() before - * calling consume_stock(). - */ - rcu_read_unlock(); - goto done; - } - /* after here, we may be blocked. we need to get refcnt */ - if (!css_tryget(&memcg->css)) { - rcu_read_unlock(); - goto again; - } - rcu_read_unlock(); + memcg = get_mem_cgroup_from_mm(mm); } + if (mem_cgroup_is_root(memcg)) + goto done; + if (consume_stock(memcg, nr_pages)) + goto done; do { bool invoke_oom = oom && !nr_oom_retries; @@ -2986,8 +2948,8 @@ again: try_to_free_mem_cgroup_pages(iter, nr_pages, gfp_mask, false); } while ((iter = parent_mem_cgroup(iter))); - css_put(&memcg->css); done: + css_put(&memcg->css); *ptr = memcg; return 0; nomem: -- 2.10.2 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
