[RFC PATCH] ANB(Automatic NUMA Balancing): erase mm footprint of migrated page

[RFC PATCH] ANB(Automatic NUMA Balancing): erase mm footprint of migrated page

[Hillf Danton]

If a page monitored by ANB is migrated, its footprint should be erased from
numa-hint-fault account, because it is no longer used. Or two pages, the
migrated page and its target page, are used in the view of task placement.


Signed-off-by: Hillf Danton <dhillf@gmail.com>
---

--- a/kernel/sched/fair.c	Wed Sep 11 18:33:00 2013
+++ b/kernel/sched/fair.c	Fri Sep 13 08:24:24 2013
@@ -1560,6 +1560,20 @@ void task_numa_fault(int last_cpupid, in
 		p->numa_pages_migrated += pages;
 
 	p->numa_faults_buffer[task_faults_idx(node, priv)] += pages;
+
+	if (migrated && last_cpupid != (-1 & LAST_CPUPID_MASK)) {
+		/* Erase footprint of migrated page */
+		int idx;
+
+		idx = cpupid_to_cpu(last_cpupid);
+		idx = cpu_to_node(idx);
+		idx = task_faults_idx(idx, priv);
+
+		if (p->numa_faults_buffer[idx] >= pages)
+		    p->numa_faults_buffer[idx] -= pages;
+		else if (p->numa_faults_buffer[idx])
+			 p->numa_faults_buffer[idx] = 0;
+	}
 }
 
 static void reset_ptenuma_scan(struct task_struct *p)
--

Re: [RFC PATCH] ANB(Automatic NUMA Balancing): erase mm footprint of migrated page

[Rik van Riel]

On 09/12/2013 08:45 PM, Hillf Danton wrote:
> If a page monitored by ANB is migrated, its footprint should be erased from
> numa-hint-fault account, because it is no longer used. Or two pages, the
> migrated page and its target page, are used in the view of task placement.
> 
> 
> Signed-off-by: Hillf Danton <dhillf@gmail.com>

NAK

The numa faults buffer contains the number of pages on each
node that the task recently faulted on.

If the page got migrated, it is only counted on the new node,
not on the old one. That means there is no need to subtract
it on the old node.

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Re: [RFC PATCH] ANB(Automatic NUMA Balancing): erase mm footprint of migrated page

[Hillf Danton]

Hello Rik

On Fri, Sep 13, 2013 at 9:41 AM, Rik van Riel <riel@redhat.com> wrote:
> On 09/12/2013 08:45 PM, Hillf Danton wrote:
>> If a page monitored by ANB is migrated, its footprint should be erased from
>> numa-hint-fault account, because it is no longer used. Or two pages, the
>> migrated page and its target page, are used in the view of task placement.
>>
>>
>> Signed-off-by: Hillf Danton <dhillf@gmail.com>
>
> NAK
>
> The numa faults buffer contains the number of pages on each
> node that the task recently faulted on.
>
> If the page got migrated, it is only counted on the new node,
> not on the old one. That means there is no need to subtract
> it on the old node.
>
Yes, I cut at wrong place.

Since old node is valid,  the footprint of migrated page already
deposits in ->numa_faults, and cut should go there.

Thanks
Hillf


--- a/kernel/sched/fair.c	Wed Sep 11 18:33:00 2013
+++ b/kernel/sched/fair.c	Fri Sep 13 14:10:34 2013
@@ -1560,6 +1560,23 @@ void task_numa_fault(int last_cpupid, in
 		p->numa_pages_migrated += pages;
 
 	p->numa_faults_buffer[task_faults_idx(node, priv)] += pages;
+
+	if (migrated && last_cpupid != (-1 & LAST_CPUPID_MASK)) {
+		/* Erase footprint of migrated page */
+		int idx;
+
+		idx = cpupid_to_cpu(last_cpupid);
+		idx = cpu_to_node(idx);
+		idx = task_faults_idx(idx, priv);
+
+		if (pages > 1)
+			pages >>= 1;
+
+		if (p->numa_faults[idx] >= pages)
+		    p->numa_faults[idx] -= pages;
+		else if (p->numa_faults[idx])
+			 p->numa_faults[idx] = 0;
+	}
 }
 
 static void reset_ptenuma_scan(struct task_struct *p)
--