Messages in this thread | | | Date | Wed, 6 Jan 2010 12:31:50 +0530 | From | Balbir Singh <> | Subject | Re: [RFC] Shared page accounting for memory cgroup |
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-01-06 13:02:58]:
> On Mon, 4 Jan 2010 06:20:31 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-01-04 09:35:28]: > > > > > On Mon, 4 Jan 2010 05:37:52 +0530 > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-01-04 08:51:08]: > > > > > > > > > On Tue, 29 Dec 2009 23:57:43 +0530 > > > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > > > > > > > Hi, Everyone, > > > > > > > > > > > > I've been working on heuristics for shared page accounting for the > > > > > > memory cgroup. I've tested the patches by creating multiple cgroups > > > > > > and running programs that share memory and observed the output. > > > > > > > > > > > > Comments? > > > > > > > > > > Hmm? Why we have to do this in the kernel ? > > > > > > > > > > > > > For several reasons that I can think of > > > > > > > > 1. With task migration changes coming in, getting consistent data free of races > > > > is going to be hard. > > > > > > Hmm, Let's see real-worlds's "ps" or "top" command. Even when there are no guarantee > > > of error range of data, it's still useful. > > > > Yes, my concern is this > > > > 1. I iterate through tasks and calculate RSS > > 2. I look at memory.usage_in_bytes > > > > If the time in user space between 1 and 2 is large I get very wrong > > results, specifically if the workload is changing its memory usage > > drastically.. no? > > > No. If it takes long time, locking fork()/exit() for such long time is the bigger > issue. > I recommend you to add memacct subsystem to sum up RSS of all processes's RSS counting > under a cgroup. Althoght it may add huge costs in page fault path but implementation > will be very simple and will not hurt realtime ops. > There will be no terrible race, I guess. >
But others hold that lock as well, simple thing like listing tasks and moving tasks, etc. I expect the usage of shared to be in the same range.
-- Balbir
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