sched/numa: Do statistics calculation using local variables only (35664fd4) · Commits · 戴 / test

The current code in task_numa_placement calculates the difference between the old and the new value, but also temporarily stores half of the old value in the per-process variables. The NUMA balancing code looks at those per-process variables, and having other tasks temporarily see halved statistics could lead to unwanted numa migrations. This can be avoided by doing all the math in local variables. This change also simplifies the code a little. Signed-off-by:

Rik van Riel <riel@redhat.com> Acked-by:

Mel Gorman <mgorman@suse.de> Signed-off-by:

Peter Zijlstra <peterz@infradead.org> Cc: Chegu Vinod <chegu_vinod@hp.com> Link: http://lkml.kernel.org/r/1390860228-21539-8-git-send-email-riel@redhat.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

+4 −8

Original line number	Diff line number	Diff line
		@@ -1513,12 +1513,9 @@ static void task_numa_placement(struct task_struct *p)
		long diff, f_diff, f_weight;

		i = task_faults_idx(nid, priv);
		diff = -p->numa_faults_memory[i];
		f_diff = -p->numa_faults_cpu[i];

		/* Decay existing window, copy faults since last scan */
		p->numa_faults_memory[i] >>= 1;
		p->numa_faults_memory[i] += p->numa_faults_buffer_memory[i];
		diff = p->numa_faults_buffer_memory[i] - p->numa_faults_memory[i] / 2;
		fault_types[priv] += p->numa_faults_buffer_memory[i];
		p->numa_faults_buffer_memory[i] = 0;

		@@ -1532,13 +1529,12 @@ static void task_numa_placement(struct task_struct *p)
		f_weight = div64_u64(runtime << 16, period + 1);
		f_weight = (f_weight * p->numa_faults_buffer_cpu[i]) /
		(total_faults + 1);
		p->numa_faults_cpu[i] >>= 1;
		p->numa_faults_cpu[i] += f_weight;
		f_diff = f_weight - p->numa_faults_cpu[i] / 2;
		p->numa_faults_buffer_cpu[i] = 0;

		p->numa_faults_memory[i] += diff;
		p->numa_faults_cpu[i] += f_diff;
		faults += p->numa_faults_memory[i];
		diff += p->numa_faults_memory[i];
		f_diff += p->numa_faults_cpu[i];
		p->total_numa_faults += diff;
		if (p->numa_group) {
		/* safe because we can only change our own group */

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