Messages in this thread Patch in this message | | | Date | Mon, 03 Dec 2012 17:46:17 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 32/52] sched: Track groups of shared tasks |
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On 12/02/2012 01:43 PM, Ingo Molnar wrote:
> This is not entirely correct as this task might have scheduled or > migrate ther - but statistically there will be correlation to the ^^^^ there?
> tasks that we share memory with, and correlation is all we need. > > We map out the relation itself by filtering out the highest address > ask that is below our own task address, per working set scan ^^^ task? > iteration.
> @@ -906,23 +945,122 @@ out_backoff: > } > > /* > + * Track our "memory buddies" the tasks we actively share memory with. > + * > + * Firstly we establish the identity of some other task that we are > + * sharing memory with by looking at rq[page::last_cpu].curr - i.e. > + * we check the task that is running on that CPU right now. > + * > + * This is not entirely correct as this task might have scheduled or > + * migrate ther - but statistically there will be correlation to the ^^^^ there
> + * tasks that we share memory with, and correlation is all we need. > + * > + * We map out the relation itself by filtering out the highest address > + * ask that is below our own task address, per working set scan ^^^ task?
If that word is "task", the comment makes sense. If it is something else, I'm back to square one on what the code does :)
> void task_numa_fault(int node, int last_cpu, int pages) > { > struct task_struct *p = current; > int priv = (task_cpu(p) == last_cpu); > + int idx = 2*node + priv; > > if (unlikely(!p->numa_faults)) { > - int size = sizeof(*p->numa_faults) * 2 * nr_node_ids; > + int entries = 2*nr_node_ids; > + int size = sizeof(*p->numa_faults) * entries; > > - p->numa_faults = kzalloc(size, GFP_KERNEL); > + p->numa_faults = kzalloc(2*size, GFP_KERNEL);
So we multiply nr_node_ids by 2. Twice.
That kind of magic deserves a comment explaining how and why. How about:
/* * We track two arrays with private and shared faults * for each NUMA node. The p->numa_faults_curr array * is allocated at the same time as the p->numa_faults * array. */ int size = sizeof(*p->numa_faults) * 4 * nr_node_ids;
> if (!p->numa_faults) > return; > + /* > + * For efficiency reasons we allocate ->numa_faults[] > + * and ->numa_faults_curr[] at once and split the > + * buffer we get. They are separate otherwise. > + */ > + p->numa_faults_curr = p->numa_faults + entries; > }
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