Messages in this thread | | | Date | Wed, 25 Nov 2009 08:49:10 +0900 | From | Daisuke Nishimura <> | Subject | Re: [BUGFIX][PATCH -mmotm] memcg: avoid oom-killing innocent task in case of use_hierarchy |
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On Tue, 24 Nov 2009 22:34:02 +0530, Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > * Daisuke Nishimura <d-nishimura@mtf.biglobe.ne.jp> [2009-11-24 23:00:29]: > > > On Tue, 24 Nov 2009 19:01:54 +0530 > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > On Tue, Nov 24, 2009 at 11:27 AM, Daisuke Nishimura > > > <nishimura@mxp.nes.nec.co.jp> wrote: > > > > task_in_mem_cgroup(), which is called by select_bad_process() to check whether > > > > a task can be a candidate for being oom-killed from memcg's limit, checks > > > > "curr->use_hierarchy"("curr" is the mem_cgroup the task belongs to). > > > > > > > > But this check return true(it's false positive) when: > > > > > > > > <some path>/00 use_hierarchy == 0 <- hitting limit > > > > <some path>/00/aa use_hierarchy == 1 <- "curr" > > > > > > > > This leads to killing an innocent task in 00/aa. This patch is a fix for this > > > > bug. And this patch also fixes the arg for mem_cgroup_print_oom_info(). We > > > > should print information of mem_cgroup which the task being killed, not current, > > > > belongs to. > > > > > > > > > > Quick Question: What happens if <some path>/00 has no tasks in it > > > after your patches? > > > > > Nothing would happen because <some path>/00 never hit its limit. > > Why not? I am talking of a scenario where <some path>/00 is set to a > limit (similar to your example) and hits its limit, but the groups > under it have no limits, but tasks. Shouldn't we be scanning > <some path>/00/aa as well? > > > > > The bug that this patch fixes is: > > > > - create a dir <some path>/00 and set some limits. > > - create a sub dir <some path>/00/aa w/o any limits, and enable hierarchy. > > - run some programs in both in 00 and 00/aa. programs in 00 should be > > big enough to cause oom by its limit. > > - when oom happens by 00's limit, tasks in 00/aa can also be killed. > > > > To be honest, the last part is fair, specifically if 00/aa has a task > that is really the heaviest task as per the oom logic. no? Are you > suggesting that only tasks in <some path>/00 should be selected by the > oom logic? > All of your comments would be rational if hierarchy is enabled in 00(it's also enabled in 00/aa automatically in this case). I'm saying about the case where it's disabled in 00 but enabled in 00/aa.
In this scenario, charges by tasks in 00/aa is(and should not be) charged to 00. And oom caused by 00's limit should not affect the task in 00/aa.
Regards, Daisuke Nishimura. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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