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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)

  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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