Re: [RFC PATCH 0/5] memcg: VM overcommit accounting and handling [message #30895] |
Tue, 10 June 2008 00:14 |
KAMEZAWA Hiroyuki
Messages: 463 Registered: September 2006
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Senior Member |
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On Tue, 10 Jun 2008 01:32:58 +0200
Andrea Righi <righi.andrea@gmail.com> wrote:
>
> Provide distinct cgroup VM overcommit accounting and handling using the memory
> resource controller.
>
Could you explain the benefits of this even when we have memrlimit controller ?
(If unsure, see 2.6.26-rc5-mm1 and search memrlimit controller.)
And this kind of virtual-address-handling things should be implemented on
memrlimit controller (means not on memory-resource-controller.).
It seems this patch doesn't need to handle page_group.
Considering hierarchy, putting several kinds of features on one controller is
not good, I think. Balbir, how do you think ?
Thanks,
-Kame
> Patchset against latest Linus git tree.
>
> This patchset allows to set different per-cgroup overcommit rules and,
> according to them, it's possible to return a memory allocation failure (ENOMEM)
> to the applications, instead of always triggering the OOM killer via
> mem_cgroup_out_of_memory() when cgroup memory limits are exceeded.
>
> Default overcommit settings are taken from vm.overcommit_memory and
> vm.overcommit_ratio sysctl values. Child cgroups initially inherits the VM
> overcommit parent's settings.
>
> Cgroup overcommit settings can be overridden using memory.overcommit_memory and
> memory.overcommit_ratio files under the cgroup filesystem.
>
> For example:
>
> 1. Initialize a cgroup with 50MB memory limit:
> # mount -t cgroup none /cgroups -o memory
> # mkdir /cgroups/0
> # /bin/echo $$ > /cgroups/0/tasks
> # /bin/echo 50M > /cgroups/0/memory.limit_in_bytes
>
> 2. Use the "never overcommit" policy with 50% ratio:
> # /bin/echo 2 > /cgroups/0/memory.overcommit_memory
> # /bin/echo 50 > /cgroups/0/memory.overcommit_ratio
>
> Assuming we have no swap space, cgroup 0 can allocate up to 25MB of virtual
> memory. If that limit is exceeded all the further allocation attempts made by
> userspace applications will receive a -ENOMEM.
>
> 4. Show committed VM statistics:
> # cat /cgroups/0/memory.overcommit_as
> CommitLimit: 25600 kB
> Committed_AS: 9844 kB
>
> 5. Use "always overcommmit":
> # /bin/echo 1 > /cgroups/0/memory.overcommit_memory
>
> This is very similar to the default memory controller configuration: overcommit
> is allowed, but when there's no more available memory oom-killer is invoked.
>
> TODO:
> - shared memory is not taken in account (i.e. files in tmpfs)
>
> -Andrea
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Re: [RFC PATCH 0/5] memcg: VM overcommit accounting and handling [message #30912 is a reply to message #30909] |
Tue, 10 June 2008 08:30 |
Andrea Righi
Messages: 65 Registered: May 2008
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Member |
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Pavel Emelyanov wrote:
> Balbir Singh wrote:
>> KAMEZAWA Hiroyuki wrote:
>>> On Tue, 10 Jun 2008 01:32:58 +0200
>>> Andrea Righi <righi.andrea@gmail.com> wrote:
>>>
>>>> Provide distinct cgroup VM overcommit accounting and handling using the memory
>>>> resource controller.
>>>>
>>> Could you explain the benefits of this even when we have memrlimit controller ?
>>> (If unsure, see 2.6.26-rc5-mm1 and search memrlimit controller.)
>>>
>>> And this kind of virtual-address-handling things should be implemented on
>>> memrlimit controller (means not on memory-resource-controller.).
>>> It seems this patch doesn't need to handle page_group.
>>>
>>> Considering hierarchy, putting several kinds of features on one controller is
>>> not good, I think. Balbir, how do you think ?
>>>
>> I would tend to agree. With the memrlimit controller, can't we do this in user
>> space now? Figure out the overcommit value and based on that setup the memrlimit?
>
> I also agree with Balbir and Kamezawa. Separate controller for VM (i.e. vma-s
> lengths) is more preferable, rather than yet another fancy feature on top of
> the existing rss one.
>
Yep! it seems I totally miss the memrlimit controller. I was trying to
implement pretty the same functionalities, using a different approach.
However, I agree that a separate controller seems to be a better
solution.
Thank you all for pointing in the right direction. I'll test memrlimit
controller and give a feedback.
-Andrea
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