On Fri 18-07-14 11:07:19, Johannes Weiner wrote: > On Thu, Jul 17, 2014 at 05:29:36PM +0200, Michal Hocko wrote: > > On Mon 07-07-14 14:55:58, Johannes Weiner wrote: > > > Pages are now uncharged at release time, and all sources of batched > > > uncharges operate on lists of pages. Directly use those lists, and > > > get rid of the per-task batching state. > > > > > > This also batches statistics accounting, in addition to the res > > > counter charges, to reduce IRQ-disabling and re-enabling. > > > > It is probably worth noticing that there is a higher chance of missing > > threshold events now when we can accumulate huge number of uncharges > > during munmaps. I do not think this is earth shattering and the overall > > improvement is worth it but changelog should mention it. > > Does this actually matter, though? We might deliver events a few > pages later than before, but as I read the threshold code, once > invoked it catches up from the last delivered threshold to the new > usage. So we shouldn't *miss* any events. You are right. I have completely miss this aspect of threshold implementation. I should have looked into the code before claiming that :/ and not focus only on the triggering code. Sorry about that! > > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > > > With the follow up fix from > > http://marc.info/?l=linux-mm&m=140552814228135&w=2 > > > > Acked-by: Michal Hocko <mhocko@xxxxxxx> > > Thanks! > > > > +static void uncharge_list(struct list_head *page_list) > > > +{ > > > + struct mem_cgroup *memcg = NULL; > > > + unsigned long nr_memsw = 0; > > > + unsigned long nr_anon = 0; > > > + unsigned long nr_file = 0; > > > + unsigned long nr_huge = 0; > > > + unsigned long pgpgout = 0; > > > + unsigned long nr_mem = 0; > > > + struct list_head *next; > > > + struct page *page; > > > + > > > + next = page_list->next; > > > + do { > > > > I would use list_for_each_entry here which would also save list_empty > > check in mem_cgroup_uncharge_list > > list_for_each_entry() wouldn't work for the singleton list where we > pass in page->lru. That's why it's a do-while that always does the > first page before checking whether it looped back to the list head. > > Do we need a comment for that? I'm not convinced, there are only two > callsites, and the one that passes the singleton page->lru is right > below this function. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>