diff options
| author | Anton Blanchard <anton@samba.org> | 2010-05-16 20:02:39 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2010-05-21 17:31:12 +1000 |
| commit | b878dc00595440586874952dd85ce9b803360b87 (patch) | |
| tree | 172832984c2ca6661cb48899c40b5734cdfa82a3 /arch/powerpc/platforms | |
| parent | dd04c63c96425af9b6741f3abf0ad25d6b1c0e8d (diff) | |
powerpc: Use smt_snooze_delay=-1 to always busy loop
Right now if we want to busy loop and not give up any time to the hypervisor
we put a very large value into smt_snooze_delay. This is sometimes useful
when running a single partition and you want to avoid any latencies due
to the hypervisor or CPU power state transitions. While this works, it's a bit
ugly - how big a number is enough now we have NO_HZ and can be idle for a very
long time.
The patch below makes smt_snooze_delay signed, and a negative value means loop
forever:
echo -1 > /sys/devices/system/cpu/cpu0/smt_snooze_delay
This change shouldn't affect the existing userspace tools (eg ppc64_cpu), but
I'm cc-ing Nathan just to be sure.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/platforms')
| -rw-r--r-- | arch/powerpc/platforms/pseries/setup.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index 6710761bf60..a6d19e3a505 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -496,13 +496,14 @@ static int __init pSeries_probe(void) } -DECLARE_PER_CPU(unsigned long, smt_snooze_delay); +DECLARE_PER_CPU(long, smt_snooze_delay); static void pseries_dedicated_idle_sleep(void) { unsigned int cpu = smp_processor_id(); unsigned long start_snooze; unsigned long in_purr, out_purr; + long snooze = __get_cpu_var(smt_snooze_delay); /* * Indicate to the HV that we are idle. Now would be @@ -517,13 +518,12 @@ static void pseries_dedicated_idle_sleep(void) * has been checked recently. If we should poll for a little * while, do so. */ - if (__get_cpu_var(smt_snooze_delay)) { - start_snooze = get_tb() + - __get_cpu_var(smt_snooze_delay) * tb_ticks_per_usec; + if (snooze) { + start_snooze = get_tb() + snooze * tb_ticks_per_usec; local_irq_enable(); set_thread_flag(TIF_POLLING_NRFLAG); - while (get_tb() < start_snooze) { + while ((snooze < 0) || (get_tb() < start_snooze)) { if (need_resched() || cpu_is_offline(cpu)) goto out; ppc64_runlatch_off(); |