Re: [patch 4/4] powerpc 2.6.21-rt1: reduce scheduling latency by changing tlb flush size

+
+#ifdef CONFIG_PREEMPT_RT
+	/*
+	 * Since flushing tlb needs expensive hypervisor call(s) on celleb,
+	 * always flush it on RT to reduce scheduling latency.
+	 */
+	if (machine_is(celleb)) {
+		flush_tlb_pending();
+		return;
+	}
+#endif /* CONFIG_PREEMPT_RT */
+
 	if (i >= PPC64_TLB_BATCH_NR)
 		flush_tlb_pending();
 }

Any reason to do that only on celleb ? :-)

Also, we might want to still batch, though in smaller amount. Have you measured
the time it takes ? We might want to modulate the amount based on wether we
are using native hash tables or an hypervisor.

Ben.