Messages in this thread | | | Date | Mon, 2 Mar 2009 23:22:35 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH 0/4] Memory controller soft limit patches (v3) |
| |
* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-02 15:18:30]:
> On Mon, 2 Mar 2009 11:35:19 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > Then, not-sorted RB-tree can be there. > > > > > > BTW, > > > time_after(jiffies, 0) > > > is buggy (see definition). If you want make this true always, > > > time_after(jiffies, jiffies +1) > > > > > > > HZ/4 is 250/4 jiffies in the worst case (62). We have > > time_after(jiffies, next_update_interval) and next_update_interval is > > set to last_tree_update + 62. Not sure if I got what you are pointing > > to. > > > + unsigned long next_update = 0; > + unsigned long flags; > + > + if (!css_tryget(&mem->css)) > + return; > + prev_usage_in_excess = mem->usage_in_excess; > + new_usage_in_excess = res_counter_soft_limit_excess(&mem->res); > + > + if (time_check) > + next_update = mem->last_tree_update + > + MEM_CGROUP_TREE_UPDATE_INTERVAL; > + if (new_usage_in_excess && time_after(jiffies, next_update)) { > + if (prev_usage_in_excess) > + mem_cgroup_remove_exceeded(mem); > + mem_cgroup_insert_exceeded(mem); > + updated_tree = true; > + } else if (prev_usage_in_excess && !new_usage_in_excess) { > + mem_cgroup_remove_exceeded(mem); > + updated_tree = true; > + } > > My point is what happens if time_check==false. > time_afrter(jiffies, 0) is buggy. >
I see your point now, but the idea behind doing so is that time_after(jiffies, 0) will always return false, which forces the prev_usage_in_excess and !new_usage_in_excess check to execute. We set the value to false only from __mem_cgroup_free().
Are you suggesting that calling time_after(jiffies, 0) is buggy? The comment
Do this with "<0" and ">=0" to only test the sign of the result. A
I think refers to the comparison check and not to the parameters. I hope I am reading this right. -- Balbir
| |