Patchwork [v6,10/10] Disable task moving when using kernel memory accounting

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Submitter Glauber Costa
Date Nov. 25, 2011, 5:38 p.m.
Message ID <1322242696-27682-11-git-send-email-glommer@parallels.com>
Download mbox | patch
Permalink /patch/127722/
State RFC
Delegated to: David Miller
Headers show

Comments

Glauber Costa - Nov. 25, 2011, 5:38 p.m.
Since this code is still experimental, we are leaving the exact
details of how to move tasks between cgroups when kernel memory
accounting is used as future work.

For now, we simply disallow movement if there are any pending
accounted memory.

Signed-off-by: Glauber Costa <glommer@parallels.com>
CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
---
 mm/memcontrol.c |   23 ++++++++++++++++++++++-
 1 files changed, 22 insertions(+), 1 deletions(-)
KAMEZAWA Hiroyuki - Nov. 28, 2011, 4:32 a.m.
On Fri, 25 Nov 2011 15:38:16 -0200
Glauber Costa <glommer@parallels.com> wrote:

> Since this code is still experimental, we are leaving the exact
> details of how to move tasks between cgroups when kernel memory
> accounting is used as future work.
> 
> For now, we simply disallow movement if there are any pending
> accounted memory.
> 
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  mm/memcontrol.c |   23 ++++++++++++++++++++++-
>  1 files changed, 22 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2df5d3c..ab7e57b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5451,10 +5451,19 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
>  {
>  	int ret = 0;
>  	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
> +	struct mem_cgroup *from = mem_cgroup_from_task(p);
> +
> +#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_INET)
> +	if (from != mem && !mem_cgroup_is_root(from) &&
> +	    res_counter_read_u64(&from->tcp_mem.tcp_memory_allocated, RES_USAGE)) {
> +		printk(KERN_WARNING "Can't move tasks between cgroups: "
> +			"Kernel memory held. task: %s\n", p->comm);
> +		return 1;
> +	}
> +#endif

Hmm, the kernel memory is not guaranteed as being held by the 'task' ?

How about
"Now, moving task between cgroup is disallowed while the source cgroup 
 containes kmem reference." ?

Hmm.. we need to fix this task-move/rmdir issue before production use.


Thanks,
-Kame

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Glauber Costa - Nov. 28, 2011, 11 a.m.
On 11/28/2011 02:32 AM, KAMEZAWA Hiroyuki wrote:
> On Fri, 25 Nov 2011 15:38:16 -0200
> Glauber Costa<glommer@parallels.com>  wrote:
>
>> Since this code is still experimental, we are leaving the exact
>> details of how to move tasks between cgroups when kernel memory
>> accounting is used as future work.
>>
>> For now, we simply disallow movement if there are any pending
>> accounted memory.
>>
>> Signed-off-by: Glauber Costa<glommer@parallels.com>
>> CC: Hiroyouki Kamezawa<kamezawa.hiroyu@jp.fujitsu.com>
>> ---
>>   mm/memcontrol.c |   23 ++++++++++++++++++++++-
>>   1 files changed, 22 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 2df5d3c..ab7e57b 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -5451,10 +5451,19 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
>>   {
>>   	int ret = 0;
>>   	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
>> +	struct mem_cgroup *from = mem_cgroup_from_task(p);
>> +
>> +#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM)&&  defined(CONFIG_INET)
>> +	if (from != mem&&  !mem_cgroup_is_root(from)&&
>> +	    res_counter_read_u64(&from->tcp_mem.tcp_memory_allocated, RES_USAGE)) {
>> +		printk(KERN_WARNING "Can't move tasks between cgroups: "
>> +			"Kernel memory held. task: %s\n", p->comm);
>> +		return 1;
>> +	}
>> +#endif
>
> Hmm, the kernel memory is not guaranteed as being held by the 'task' ?
>
> How about
> "Now, moving task between cgroup is disallowed while the source cgroup
>   containes kmem reference." ?
>
> Hmm.. we need to fix this task-move/rmdir issue before production use.
>
>
> Thanks,
> -Kame
>
Hi Kame,

Let me tell you the direction I am going wrt task movement: The only 
reasons I haven't included so far, is that I believe it needs more 
testing, and as you know, I am right now more interested in getting past 
the initial barriers for inclusion. I am committed to fix anything that 
needs to be fixed - stylish or non-stylish before we remove the 
experimental flag.

So what I intend to do, is to basically
* lock the task,
* scan through its file descriptors list,
* identify which of them are sockets,
* cast them to struct sock *,
* see if it has a cgrp associated
* see if cgrp == from

At this point we can decrement sockets allocated by 1 in from, and 
memory_allocated by sk_forward_alloc (increasing by equal quantities in 
the destination cgroup)

I belive it will work.


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Patch

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2df5d3c..ab7e57b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5451,10 +5451,19 @@  static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 {
 	int ret = 0;
 	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
+	struct mem_cgroup *from = mem_cgroup_from_task(p);
+
+#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_INET)
+	if (from != mem && !mem_cgroup_is_root(from) &&
+	    res_counter_read_u64(&from->tcp_mem.tcp_memory_allocated, RES_USAGE)) {
+		printk(KERN_WARNING "Can't move tasks between cgroups: "
+			"Kernel memory held. task: %s\n", p->comm);
+		return 1;
+	}
+#endif
 
 	if (mem->move_charge_at_immigrate) {
 		struct mm_struct *mm;
-		struct mem_cgroup *from = mem_cgroup_from_task(p);
 
 		VM_BUG_ON(from == mem);
 
@@ -5622,6 +5631,18 @@  static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
 				struct task_struct *p)
 {
+	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
+	struct mem_cgroup *from = mem_cgroup_from_task(p);
+
+#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_INET)
+	if (from != mem && !mem_cgroup_is_root(from) &&
+	    res_counter_read_u64(&from->tcp_mem.tcp_memory_allocated, RES_USAGE)) {
+		printk(KERN_WARNING "Can't move tasks between cgroups: "
+			"Kernel memory held. task: %s\n", p->comm);
+		return 1;
+	}
+#endif
+
 	return 0;
 }
 static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,