[PATCH] Subject: Re: Help understanding slow down

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Add a warning that "idle=poll" is a performance hit on hyperthreaded CPUs.

arch/i386/kernel/process.c

@@ -202,6 +202,10 @@ static int __init idle_setup (char *str)
 	if (!strncmp(str, "poll", 4)) {
 		printk("using polling idle threads.\n");
 		pm_idle = poll_idle;
+#ifdef CONFIG_SMP
+		if (smp_num_siblings > 1)
+			printk("WARNING: polling idle and HT enabled, performance may degrade.\n");
+#endif
 	} else if (!strncmp(str, "halt", 4)) {
 		printk("using halt in idle threads.\n");
 		pm_idle = default_idle;