From: Joel Schopp <jschopp@austin.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: ego@in.ibm.com, linux-kernel@vger.kernel.org,
Ingo Molnar <mingo@elte.hu>,
linuxppc-dev@lists.ozlabs.org
Subject: [PATCHv4 2/2] powerpc: implement arch_scale_smt_power for Power7
Date: Fri, 05 Feb 2010 14:57:58 -0600 [thread overview]
Message-ID: <1265403478.6089.41.camel@jschopp-laptop> (raw)
In-Reply-To: <1264721088.10385.1.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>
---
Version 3 adds the #ifdef to avoid compiling on kernels that don't need it
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
@@ -620,3 +620,61 @@ void __cpu_die(unsigned int cpu)
smp_ops->cpu_die(cpu);
}
#endif
+
+#ifdef CONFIG_SCHED_SMT
+unsigned long arch_scale_smt_power(struct sched_domain *sd, int cpu)
+{
+ int sibling;
+ int idle_count = 0;
+ int thread;
+
+ /* Setup the default weight and smt_gain used by most cpus for SMT
+ * Power. Doing this right away covers the default case and can be
+ * used by cpus that modify it dynamically.
+ */
+ struct cpumask *sibling_map = sched_domain_span(sd);
+ unsigned long weight = cpumask_weight(sibling_map);
+ unsigned long smt_gain = sd->smt_gain;
+
+
+ if (cpu_has_feature(CPU_FTR_ASYNC_SMT4) && weight == 4) {
+ for_each_cpu(sibling, sibling_map) {
+ if (idle_cpu(sibling))
+ idle_count++;
+ }
+
+ /* the following section attempts to tweak cpu power based
+ * on current idleness of the threads dynamically at runtime
+ */
+ if (idle_count > 1) {
+ thread = cpu_thread_in_core(cpu);
+ if (thread < 2) {
+ /* 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 */
+ switch (weight) {
+ case 1:
+ /*divide by 1, do nothing*/
+ break;
+ case 2:
+ smt_gain = smt_gain >> 1;
+ break;
+ case 4:
+ smt_gain = smt_gain >> 2;
+ break;
+ default:
+ smt_gain /= weight;
+ break;
+ }
+
+ return smt_gain;
+
+}
+#endif
Index: linux-2.6.git/arch/powerpc/include/asm/cputable.h
===================================================================
--- linux-2.6.git.orig/arch/powerpc/include/asm/cputable.h
+++ linux-2.6.git/arch/powerpc/include/asm/cputable.h
@@ -195,6 +195,7 @@ extern const char *powerpc_base_platform
#define CPU_FTR_SAO LONG_ASM_CONST(0x0020000000000000)
#define CPU_FTR_CP_USE_DCBTZ LONG_ASM_CONST(0x0040000000000000)
#define CPU_FTR_UNALIGNED_LD_STD LONG_ASM_CONST(0x0080000000000000)
+#define CPU_FTR_ASYNC_SMT4 LONG_ASM_CONST(0x0100000000000000)
#ifndef __ASSEMBLY__
@@ -409,7 +410,7 @@ extern const char *powerpc_base_platform
CPU_FTR_MMCRA | CPU_FTR_SMT | \
CPU_FTR_COHERENT_ICACHE | CPU_FTR_LOCKLESS_TLBIE | \
CPU_FTR_PURR | CPU_FTR_SPURR | CPU_FTR_REAL_LE | \
- CPU_FTR_DSCR | CPU_FTR_SAO)
+ CPU_FTR_DSCR | CPU_FTR_SAO | CPU_FTR_ASYNC_SMT4)
#define CPU_FTRS_CELL (CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \
CPU_FTR_PPCAS_ARCH_V2 | CPU_FTR_CTRL | \
CPU_FTR_ALTIVEC_COMP | CPU_FTR_MMCRA | CPU_FTR_SMT | \
next prev parent reply other threads:[~2010-02-05 20:58 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 ` [PATCH 2/2] powerpc: implement arch_scale_smt_power for Power7 Joel Schopp
2010-01-20 20:48 ` 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 ` Joel Schopp [this message]
2010-02-14 10:12 ` [PATCHv4 " 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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