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Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller [message #44476 is a reply to message #44390]

Fri, 09 December 2011 14:48

Glauber Costa
Messages: 916
Registered: October 2011

Senior Member

On 12/09/2011 12:44 PM, David Laight wrote:
>
>> How about this?
>>
>> val = !!val;
>>
>> /*
>> * This follows the same hierarchy restrictions than
>> * mem_cgroup_hierarchy_write()
>> */
>> if (!parent || !parent->use_hierarchy) {
>> if (list_empty(&cgroup->children))
>> memcg->kmem_independent_accounting = val;
>> else
>> return -EBUSY;
>> }
>> else
>> return -EINVAL;
>>
>> return 0;
>
> Inverting the tests gives easier to read code:
>
> if (parent&& parent->user_hierarchy)
> return -EINVAL;
> if (!list_empty(&cgroup->children))
> return -EBUSY;
> memcg->kmem_independent_accounting = val != 0;
> return 0;

On the other hand, inconsistent with mem_cgroup_hierarchy_write(), which
applies the logic in the same way I did here.

> NFI about the logic...
> On the face of it the tests don't seem related to each other
> or to the assignment!

How so?

If parent's use_hierarchy is set, we can't set this value (we need to
have a parent for that to even matter).

We also can't set it if we already have any children - otherwise all the
on-the-fly adjustments become hell-on-earth.

As for = val != 0, sorry, but I completely disagree this is easier than
!!val. Not to mention the !!val notation is already pretty widespread in
the kernel.

> David
>
>
>
>
> --
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[Message index]

		[PATCH v8 0/9] per-cgroup tcp memory pressure controls By: Glauber Costa on Mon, 05 December 2011 21:34
		[PATCH v8 2/9] foundations of per-cgroup memory pressure controlling. By: Glauber Costa on Mon, 05 December 2011 21:34
		Re: [PATCH v8 2/9] foundations of per-cgroup memory pressure controlling. By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:24
		Re: [PATCH v8 2/9] foundations of per-cgroup memory pressure controlling. By: Glauber Costa on Fri, 09 December 2011 12:41
		[PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: Glauber Costa on Mon, 05 December 2011 21:34
		Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:21
		Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: Glauber Costa on Fri, 09 December 2011 12:40
		Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: Glauber Costa on Fri, 09 December 2011 14:37
		Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: KAMEZAWA Hiroyuki on Mon, 12 December 2011 00:34
		RE: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: David Laight on Fri, 09 December 2011 14:44
		Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller By: Glauber Costa on Fri, 09 December 2011 14:48
		[PATCH v8 3/9] socket: initial cgroup code. By: Glauber Costa on Mon, 05 December 2011 21:34
		Re: [PATCH v8 3/9] socket: initial cgroup code. By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:49
		Re: [PATCH v8 3/9] socket: initial cgroup code. By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 02:05
		Re: [PATCH v8 3/9] socket: initial cgroup code. By: Glauber Costa on Fri, 09 December 2011 12:43
		Re: [PATCH v8 3/9] socket: initial cgroup code. By: KAMEZAWA Hiroyuki on Mon, 12 December 2011 00:33
		[PATCH v8 5/9] per-netns ipv4 sysctl_tcp_mem By: Glauber Costa on Mon, 05 December 2011 21:34
		Re: [PATCH v8 5/9] per-netns ipv4 sysctl_tcp_mem By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:54
		[PATCH v8 6/9] tcp buffer limitation: per-cgroup limit By: Glauber Costa on Mon, 05 December 2011 21:35
		Re: [PATCH v8 6/9] tcp buffer limitation: per-cgroup limit By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:55
		[PATCH v8 7/9] Display current tcp memory allocation in kmem cgroup By: Glauber Costa on Mon, 05 December 2011 21:35
		Re: [PATCH v8 7/9] Display current tcp memory allocation in kmem cgroup By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:56
		[PATCH v8 8/9] Display current tcp failcnt in kmem cgroup By: Glauber Costa on Mon, 05 December 2011 21:35
		[PATCH v8 9/9] Display maximum tcp memory allocation in kmem cgroup By: Glauber Costa on Mon, 05 December 2011 21:35
		Re: [PATCH v8 9/9] Display maximum tcp memory allocation in kmem cgroup By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:57
		[PATCH v8 4/9] tcp memory pressure controls By: Glauber Costa on Mon, 05 December 2011 21:34
		Re: [PATCH v8 4/9] tcp memory pressure controls By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:51
		Re: [PATCH v8 0/9] per-cgroup tcp memory pressure controls By: Glauber Costa on Wed, 07 December 2011 11:06
		Re: [PATCH v8 0/9] per-cgroup tcp memory pressure controls By: KAMEZAWA Hiroyuki on Fri, 09 December 2011 01:04

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