From: akpm@linux-foundation.org
To: lenb@kernel.org
Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, davej@redhat.com, efault@gmx.de,
len.brown@intel.com, mingo@elte.hu, rusty@rustcorp.com.au,
tglx@linutronix.de, venkatesh.pallipadi@intel.com,
yakui.zhao@intel.com, yanmin_zhang@linux.intel.com
Subject: [patch for 2.6.30 2/2] arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c: avoid cross-CPU interrupts
Date: Fri, 10 Apr 2009 23:17:18 -0700 [thread overview]
Message-ID: <200904110617.n3B6HJ7W026502@imap1.linux-foundation.org> (raw)
From: Andrew Morton <akpm@linux-foundation.org>
In drv_read(), check to see whether we can run the rdmsr() on the current
CPU. If so, do that. So smp_call_function_single() can avoid the IPI.
Arguably, cpumask_any() should do this.
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff -puN arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c~arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts
+++ a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -197,9 +197,22 @@ static void do_drv_write(void *_cmd)
static void drv_read(struct drv_cmd *cmd)
{
- cmd->val = 0;
+ int target_cpu; /* The CPU on which to perform thr rdmsr() */
+ int this_cpu;
+
+ /*
+ * If the current CPU is in cmd->mask then run the rdmsr() on this
+ * CPU to avoid the cross-cpu interrupt.
+ */
+ this_cpu = get_cpu();
+ if (cpu_isset(this_cpu, *(cmd->mask)))
+ target_cpu = this_cpu;
+ else
+ target_cpu = cpumask_any(cmd->mask);
- smp_call_function_single(cpumask_any(cmd->mask), do_drv_read, cmd, 1);
+ cmd->val = 0;
+ smp_call_function_single(target_cpu, do_drv_read, cmd, 1);
+ put_cpu();
}
static void drv_write(struct drv_cmd *cmd)
_
next reply other threads:[~2009-04-11 6:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-11 6:17 akpm [this message]
2009-04-11 6:37 ` [patch for 2.6.30 2/2] arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c: avoid cross-CPU interrupts Jaswinder Singh Rajput
2009-04-12 0:06 ` Dave Jones
2009-04-12 0:46 ` Andrew Morton
2009-04-14 8:51 ` Rusty Russell
2009-04-14 17:18 ` Andrew Morton
2009-04-15 6:35 ` Rusty Russell
2009-04-20 3:22 ` Len Brown
2009-04-20 2:57 ` Len Brown
2009-04-20 3:20 ` Andrew Morton
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