From: Joel Schopp <jschopp@austin.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
ego@in.ibm.com
Subject: [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7
Date: Wed, 20 Jan 2010 14:04:07 -0600 [thread overview]
Message-ID: <1264017847.5717.132.camel@jschopp-laptop> (raw)
In-Reply-To: <1264017638.5717.121.camel@jschopp-laptop>
On Power7 processors running in SMT4 mode with 2, 3, or 4 idle threads
there is performance benefit to idling the higher numbered threads in
the core.
This patch implements arch_scale_smt_power to dynamically update smt
thread power in these idle cases in order to prefer threads 0,1 over
threads 2,3 within a core.
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
---
Index: linux-2.6.git/arch/powerpc/kernel/smp.c
===================================================================
--- linux-2.6.git.orig/arch/powerpc/kernel/smp.c
+++ linux-2.6.git/arch/powerpc/kernel/smp.c
@@ -617,3 +617,44 @@ void __cpu_die(unsigned int cpu)
smp_ops->cpu_die(cpu);
}
#endif
+
+static inline int thread_in_smt4core(int x)
+{
+ return x % 4;
+}
+unsigned long arch_scale_smt_power(struct sched_domain *sd, int cpu)
+{
+ int cpu2;
+ int idle_count = 0;
+
+ struct cpumask *cpu_map = sched_domain_span(sd);
+
+ unsigned long weight = cpumask_weight(cpu_map);
+ unsigned long smt_gain = sd->smt_gain;
+
+ if (cpu_has_feature(CPU_FTRS_POWER7) && weight == 4) {
+ for_each_cpu(cpu2, cpu_map) {
+ if (idle_cpu(cpu2))
+ idle_count++;
+ }
+
+ /* the following section attempts to tweak cpu power based
+ * on current idleness of the threads dynamically at runtime
+ */
+ if (idle_count == 2 || idle_count == 3 || idle_count == 4) {
+ if (thread_in_smt4core(cpu) == 0 ||
+ thread_in_smt4core(cpu) == 1) {
+ /* add 75 % to thread power */
+ smt_gain += (smt_gain >> 1) + (smt_gain >> 2);
+ } else {
+ /* subtract 75 % to thread power */
+ smt_gain = smt_gain >> 2;
+ }
+ }
+ }
+ /* default smt gain is 1178, weight is # of SMT threads */
+ smt_gain /= weight;
+
+ return smt_gain;
+
+}
Index: linux-2.6.git/kernel/sched_features.h
===================================================================
--- linux-2.6.git.orig/kernel/sched_features.h
+++ linux-2.6.git/kernel/sched_features.h
@@ -107,7 +107,7 @@ SCHED_FEAT(CACHE_HOT_BUDDY, 1)
/*
* Use arch dependent cpu power functions
*/
-SCHED_FEAT(ARCH_POWER, 0)
+SCHED_FEAT(ARCH_POWER, 1)
SCHED_FEAT(HRTICK, 0)
SCHED_FEAT(DOUBLE_TICK, 0)
next prev parent reply other threads:[~2010-01-20 20:04 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-20 20:00 [PATCH 0/2] sched: arch_scale_smt_powers Joel Schopp
2010-01-20 20:02 ` [PATCH 1/2] sched: Fix the place where group powers are updated Joel Schopp
2010-01-26 23:28 ` [PATCHv2 1/2] sched: enable ARCH_POWER Joel Schopp
2010-01-28 23:20 ` [PATCHv3 " Joel Schopp
2010-02-05 20:57 ` [PATCHv4 " Joel Schopp
2010-01-20 20:04 ` Joel Schopp [this message]
2010-01-20 20:48 ` [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7 Peter Zijlstra
2010-01-20 21:58 ` Michael Neuling
2010-01-20 22:44 ` Joel Schopp
2010-01-21 8:27 ` Peter Zijlstra
2010-01-20 21:04 ` Michael Neuling
2010-01-20 22:09 ` Joel Schopp
2010-01-24 3:00 ` Benjamin Herrenschmidt
2010-01-25 17:50 ` Joel Schopp
2010-01-26 4:23 ` Benjamin Herrenschmidt
2010-01-20 21:33 ` Benjamin Herrenschmidt
2010-01-20 22:36 ` Joel Schopp
2010-01-26 23:28 ` [PATCHv2 " Joel Schopp
2010-01-27 0:52 ` Benjamin Herrenschmidt
2010-01-28 22:39 ` Joel Schopp
2010-01-29 1:23 ` Benjamin Herrenschmidt
2010-01-28 23:20 ` [PATCHv3 " Joel Schopp
2010-01-28 23:24 ` Joel Schopp
2010-01-29 1:23 ` Benjamin Herrenschmidt
2010-01-29 10:13 ` Peter Zijlstra
2010-01-29 18:34 ` Joel Schopp
2010-01-29 18:41 ` Joel Schopp
2010-02-05 20:57 ` [PATCHv4 " Joel Schopp
2010-02-14 10:12 ` Peter Zijlstra
2010-02-17 22:20 ` Michael Neuling
2010-02-18 13:17 ` Peter Zijlstra
2010-02-18 13:19 ` Peter Zijlstra
2010-02-18 16:28 ` Joel Schopp
2010-02-18 17:08 ` Peter Zijlstra
2010-02-19 6:05 ` Michael Neuling
2010-02-19 10:01 ` Peter Zijlstra
2010-02-19 11:01 ` Michael Neuling
2010-02-23 6:08 ` Michael Neuling
2010-02-23 16:24 ` Peter Zijlstra
2010-02-23 16:30 ` Peter Zijlstra
2010-02-24 6:07 ` Michael Neuling
2010-02-24 11:13 ` Michael Neuling
2010-02-24 11:58 ` Michael Neuling
2010-02-27 10:21 ` Michael Neuling
2010-03-02 14:44 ` Peter Zijlstra
2010-03-04 22:28 ` Michael Neuling
2010-01-29 12:25 ` [PATCHv3 " Gabriel Paubert
2010-01-29 16:26 ` Joel Schopp
2010-01-26 23:27 ` [PATCHv2 0/2] sched: arch_scale_smt_powers v2 Joel Schopp
2010-01-28 23:20 ` [PATCHv3 0/2] sched: arch_scale_smt_powers Joel Schopp
2010-02-05 20:57 ` [PATCHv4 " Joel Schopp
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