From: Anton Blanchard <anton@ozlabs.org>
To: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
svaidy@linux.vnet.ibm.com, ego@linux.vnet.ibm.com,
rjw@rjwysocki.net, daniel.lezcano@linaro.org, npiggin@gmail.com
Cc: linuxppc-dev@lists.ozlabs.org, linux-pm@vger.kernel.org
Subject: [PATCH 3/3] cpuidle: powernv: Avoid a branch in the core snooze_loop() loop
Date: Tue, 4 Apr 2017 07:54:14 +1000 [thread overview]
Message-ID: <20170403215414.16951-3-anton@ozlabs.org> (raw)
In-Reply-To: <20170403215414.16951-1-anton@ozlabs.org>
From: Anton Blanchard <anton@samba.org>
When in the snooze_loop() we want to take up the least amount of
resources. On my version of gcc (6.3), we end up with an extra
branch because it predicts snooze_timeout_en to be false, whereas it
is almost always true.
Use likely() to avoid the branch and be a little nicer to the
other non idle threads on the core.
Signed-off-by: Anton Blanchard <anton@samba.org>
---
drivers/cpuidle/cpuidle-powernv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 8c991c254b95..251a60bfa8ee 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -58,7 +58,7 @@ static int snooze_loop(struct cpuidle_device *dev,
ppc64_runlatch_off();
HMT_very_low();
while (!need_resched()) {
- if (snooze_timeout_en && get_tb() > snooze_exit_time)
+ if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time)
break;
}
--
2.11.0
next prev parent reply other threads:[~2017-04-03 21:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-03 21:54 [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority Anton Blanchard
2017-04-03 21:54 ` [PATCH 2/3] cpuidle: powernv: Don't continually set thread priority in snooze_loop() Anton Blanchard
2017-04-04 4:06 ` Vaidyanathan Srinivasan
2017-04-03 21:54 ` Anton Blanchard [this message]
2017-04-03 23:54 ` [PATCH 3/3] cpuidle: powernv: Avoid a branch in the core snooze_loop() loop Nicholas Piggin
2017-04-04 4:10 ` Vaidyanathan Srinivasan
2017-04-03 23:52 ` [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority Nicholas Piggin
2017-04-04 4:13 ` Vaidyanathan Srinivasan
2017-04-04 4:04 ` Vaidyanathan Srinivasan
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