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Message-ID: <18995.39910.109998.926269@cargo.ozlabs.ibm.com>
Date: Sat, 13 Jun 2009 22:30:30 +1000
From: Paul Mackerras <paulus@...ba.org>
To: benh@...nel.crashing.org, linuxppc-dev@...abs.org
CC: Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel@...r.kernel.org
Subject: [PATCH RFC] powerpc: perf_counter: Enable use of software
counters on 32-bit powerpc
This enables the perf_counter subsystem on 32-bit powerpc. Since we
don't have any support for hardware counters on 32-bit powerpc yet,
only software counters can be used.
Besides selecting HAVE_PERF_COUNTERS for 32-bit powerpc as well as
64-bit, the main thing this does is add an implementation of
set_perf_counter_pending(). This needs to arrange for
perf_counter_do_pending() to be called when interrupts are enabled.
Rather than add code to local_irq_restore as 64-bit does, the 32-bit
set_perf_counter_pending() generates an interrupt by setting the
decrementer to 1 so that a decrementer interrupt will become pending
in 1 or 2 timebase ticks (if a decrementer interrupt isn't already
pending). When interrupts are enabled, timer_interrupt() will be
called, and some new code in there calls perf_counter_do_pending().
We use a per-cpu array of flags to indicate whether we need to call
perf_counter_do_pending() or not.
Signed-off-by: Paul Mackerras <paulus@...ba.org>
---
This patch depends on my 2 patches that provide an atomic64_t
implementation on 32-bit powerpc.
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/hw_irq.h | 5 ++++-
arch/powerpc/include/asm/perf_counter.h | 8 ++++++++
arch/powerpc/kernel/Makefile | 2 +-
arch/powerpc/kernel/time.c | 25 +++++++++++++++++++++++++
arch/powerpc/platforms/Kconfig.cputype | 1 -
6 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 3f0a983..c531abc 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -126,6 +126,7 @@ config PPC
select HAVE_OPROFILE
select HAVE_SYSCALL_WRAPPERS if PPC64
select GENERIC_ATOMIC64 if PPC32
+ select HAVE_PERF_COUNTERS
config EARLY_PRINTK
bool
diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index b7f8f4a..5b7ebf9 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -131,6 +131,8 @@ static inline int irqs_disabled_flags(unsigned long flags)
struct irq_chip;
#ifdef CONFIG_PERF_COUNTERS
+
+#ifdef CONFIG_PPC64
static inline unsigned long test_perf_counter_pending(void)
{
unsigned long x;
@@ -154,8 +156,9 @@ static inline void clear_perf_counter_pending(void)
"r" (0),
"i" (offsetof(struct paca_struct, perf_counter_pending)));
}
+#endif /* CONFIG_PPC64 */
-#else
+#else /* CONFIG_PERF_COUNTERS */
static inline unsigned long test_perf_counter_pending(void)
{
diff --git a/arch/powerpc/include/asm/perf_counter.h b/arch/powerpc/include/asm/perf_counter.h
index cc7c887..df6c1fe 100644
--- a/arch/powerpc/include/asm/perf_counter.h
+++ b/arch/powerpc/include/asm/perf_counter.h
@@ -9,6 +9,7 @@
* 2 of the License, or (at your option) any later version.
*/
#include <linux/types.h>
+#include <linux/percpu.h>
#define MAX_HWCOUNTERS 8
#define MAX_EVENT_ALTERNATIVES 8
@@ -53,12 +54,19 @@ extern struct power_pmu *ppmu;
#define PPMU_LIMITED_PMC_REQD 2 /* have to put this on a limited PMC */
#define PPMU_ONLY_COUNT_RUN 4 /* only counting in run state */
+#ifdef CONFIG_PPC64
struct pt_regs;
extern unsigned long perf_misc_flags(struct pt_regs *regs);
#define perf_misc_flags(regs) perf_misc_flags(regs)
+#endif /* CONFIG_PPC64 */
extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
+#ifdef CONFIG_PPC32
+DECLARE_PER_CPU(u8, perf_counter_pending);
+extern void set_perf_counter_pending(void);
+#endif
+
/*
* The power_pmu.get_constraint function returns a 64-bit value and
* a 64-bit mask that express the constraints between this event and
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index a2c6834..26db8ae 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -94,7 +94,7 @@ obj64-$(CONFIG_AUDIT) += compat_audit.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
-obj-$(CONFIG_PERF_COUNTERS) += perf_counter.o power4-pmu.o ppc970-pmu.o \
+obj64-$(CONFIG_PERF_COUNTERS) += perf_counter.o power4-pmu.o ppc970-pmu.o \
power5-pmu.o power5+-pmu.o power6-pmu.o \
power7-pmu.o
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 48571ac..f9b718c 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -52,6 +52,7 @@
#include <linux/jiffies.h>
#include <linux/posix-timers.h>
#include <linux/irq.h>
+#include <linux/perf_counter.h>
#include <asm/io.h>
#include <asm/processor.h>
@@ -524,6 +525,26 @@ void __init iSeries_time_init_early(void)
}
#endif /* CONFIG_PPC_ISERIES */
+#if defined(CONFIG_PERF_COUNTERS) && defined(CONFIG_PPC32)
+DEFINE_PER_CPU(u8, perf_counter_pending);
+
+extern void set_perf_counter_pending(void)
+{
+ get_cpu_var(perf_counter_pending) = 1;
+ set_dec(1);
+ put_cpu_var(perf_counter_pending);
+}
+
+#define test_perf_counter_pending() __get_cpu_var(perf_counter_pending)
+#define clear_perf_counter_pending() __get_cpu_var(perf_counter_pending) = 0
+
+#else /* CONFIG_PERF_COUNTERS && CONFIG_PPC32 */
+
+#define test_perf_counter_pending() 0
+#define clear_perf_counter_pending()
+
+#endif /* CONFIG_PERF_COUNTERS && CONFIG_PPC32 */
+
/*
* For iSeries shared processors, we have to let the hypervisor
* set the hardware decrementer. We set a virtual decrementer
@@ -550,6 +571,10 @@ void timer_interrupt(struct pt_regs * regs)
set_dec(DECREMENTER_MAX);
#ifdef CONFIG_PPC32
+ if (test_perf_counter_pending()) {
+ clear_perf_counter_pending();
+ perf_counter_do_pending();
+ }
if (atomic_read(&ppc_n_lost_interrupts) != 0)
do_IRQ(regs);
#endif
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 732ee93..9da795e 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -1,7 +1,6 @@
config PPC64
bool "64-bit kernel"
default n
- select HAVE_PERF_COUNTERS
help
This option selects whether a 32-bit or a 64-bit kernel
will be built.
--
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