Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller

On 12/08/2011 11:21 PM, KAMEZAWA Hiroyuki wrote:

On Mon,  5 Dec 2011 19:34:55 -0200
Glauber Costa[off-list ref]  wrote:

quoted

This patch lays down the foundation for the kernel memory component
of the Memory Controller.

As of today, I am only laying down the following files:

  * memory.independent_kmem_limit
  * memory.kmem.limit_in_bytes (currently ignored)
  * memory.kmem.usage_in_bytes (always zero)

Signed-off-by: Glauber Costa<redacted>
Reviewed-by: Kirill A. Shutemov<redacted>
CC: Paul Menage<redacted>
CC: Greg Thelen<redacted>

As I wrote, please CC Johannes and  Michal Hocko for memcg related parts.

I forgot to add them to the patch itself, but they are in the CC list of 
the messages.

So they did get the mail.

A few questions.
==

quoted

+	val = !!val;
+
+	if (parent&&  parent->use_hierarchy&&
+	   (val != parent->kmem_independent_accounting))
+		return -EINVAL;

==
Hm, why you check val != parent->kmem_independent_accounting ?

	if (parent&&  parent->use_hierarchy)
		return -EINVAL;
?

Because I thought that making sure that everybody in the chain is 
consistent, it will make things simpler for us. But I am happy to change 
that if you prefer.

BTW, you didn't check this cgroup has children or not.
I think

	if (this_cgroup->use_hierarchy&&
              !list_empty(this_cgroup->childlen))
		return -EINVAL;

Noted.

==

quoted

+	/*
+	 * TODO: We need to handle the case in which we are doing
+	 * independent kmem accounting as authorized by our parent,
+	 * but then our parent changes its parameter.
+	 */
+	cgroup_lock();
+	memcg->kmem_independent_accounting = val;
+	cgroup_unlock();

Do we need cgroup_lock() here ?

Well, I removed almost all instances of it from previous patches, so I 
guess this one can go as well.

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