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Subject[PATCH v5 2/3] powerpc/time: Only set CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC64
Date
scaled cputime is only meaningfull when the processor has
SPURR and/or PURR, which means only on PPC64.

Removing it on PPC32 significantly reduces the size of
vtime_account_system() and vtime_account_idle() on an 8xx:

Before:
00000000 l F .text 000000a8 vtime_delta
00000280 g F .text 0000010c vtime_account_system
0000038c g F .text 00000048 vtime_account_idle

After:
(vtime_delta gets inlined inside the two functions)
000001d8 g F .text 000000a0 vtime_account_system
00000278 g F .text 00000038 vtime_account_idle

In terms of performance, we also get approximatly 7% improvement on
task switch. The following small benchmark app is run with perf stat:

void *thread(void *arg)
{
int i;

for (i = 0; i < atoi((char*)arg); i++)
pthread_yield();
}

int main(int argc, char **argv)
{
pthread_t th1, th2;

pthread_create(&th1, NULL, thread, argv[1]);
pthread_create(&th2, NULL, thread, argv[1]);
pthread_join(th1, NULL);
pthread_join(th2, NULL);

return 0;
}

Before the patch:

Performance counter stats for 'chrt -f 98 ./sched 100000' (50 runs):

8228.476465 task-clock (msec) # 0.954 CPUs utilized ( +- 0.23% )
200004 context-switches # 0.024 M/sec ( +- 0.00% )

After the patch:

Performance counter stats for 'chrt -f 98 ./sched 100000' (50 runs):

7649.070444 task-clock (msec) # 0.955 CPUs utilized ( +- 0.27% )
200004 context-switches # 0.026 M/sec ( +- 0.00% )

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
v5: New (previous patch splitted in two parts)

arch/powerpc/Kconfig | 2 +-
arch/powerpc/include/asm/accounting.h | 4 ++++
arch/powerpc/include/asm/cputime.h | 1 -
arch/powerpc/kernel/time.c | 12 ++++++++++--
arch/powerpc/xmon/xmon.c | 4 ++++
5 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5eb4d969afbf..1f5ce708a650 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,7 +137,7 @@ config PPC
select ARCH_HAS_PMEM_API if PPC64
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_MEMBARRIER_CALLBACKS
- select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE
+ select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC64
select ARCH_HAS_SG_CHAIN
select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/powerpc/include/asm/accounting.h b/arch/powerpc/include/asm/accounting.h
index 3abcf98ed2e0..c607c5d835cc 100644
--- a/arch/powerpc/include/asm/accounting.h
+++ b/arch/powerpc/include/asm/accounting.h
@@ -15,8 +15,10 @@ struct cpu_accounting_data {
/* Accumulated cputime values to flush on ticks*/
unsigned long utime;
unsigned long stime;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
unsigned long utime_scaled;
unsigned long stime_scaled;
+#endif
unsigned long gtime;
unsigned long hardirq_time;
unsigned long softirq_time;
@@ -25,8 +27,10 @@ struct cpu_accounting_data {
/* Internal counters */
unsigned long starttime; /* TB value snapshot */
unsigned long starttime_user; /* TB value on exit to usermode */
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
unsigned long startspurr; /* SPURR value snapshot */
unsigned long utime_sspurr; /* ->user_time when ->startspurr set */
+#endif
};

#endif
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index 133672744b2e..ae73dc8da2d4 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -61,7 +61,6 @@ static inline void arch_vtime_task_switch(struct task_struct *prev)
struct cpu_accounting_data *acct0 = get_accounting(prev);

acct->starttime = acct0->starttime;
- acct->startspurr = acct0->startspurr;
}
#endif

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 6196bd7393a3..3b03731221c1 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -175,7 +175,7 @@ static void calc_cputime_factors(void)
* Read the SPURR on systems that have it, otherwise the PURR,
* or if that doesn't exist return the timebase value passed in.
*/
-static unsigned long read_spurr(unsigned long tb)
+static inline unsigned long read_spurr(unsigned long tb)
{
if (cpu_has_feature(CPU_FTR_SPURR))
return mfspr(SPRN_SPURR);
@@ -284,7 +284,8 @@ static inline u64 calculate_stolen_time(u64 stop_tb)
static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct,
unsigned long now, unsigned long stime)
{
- unsigned long stime_scaled;
+ unsigned long stime_scaled = 0;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
unsigned long nowscaled, deltascaled;
unsigned long utime, utime_scaled;

@@ -315,6 +316,7 @@ static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct,
}
}
acct->utime_scaled += utime_scaled;
+#endif

return stime_scaled;
}
@@ -351,7 +353,9 @@ void vtime_account_system(struct task_struct *tsk)

if ((tsk->flags & PF_VCPU) && !irq_count()) {
acct->gtime += stime;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
acct->utime_scaled += stime_scaled;
+#endif
} else {
if (hardirq_count())
acct->hardirq_time += stime;
@@ -360,7 +364,9 @@ void vtime_account_system(struct task_struct *tsk)
else
acct->stime += stime;

+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
acct->stime_scaled += stime_scaled;
+#endif
}
}
EXPORT_SYMBOL_GPL(vtime_account_system);
@@ -377,6 +383,7 @@ void vtime_account_idle(struct task_struct *tsk)
static void vtime_flush_scaled(struct task_struct *tsk,
struct cpu_accounting_data *acct)
{
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
if (acct->utime_scaled)
tsk->utimescaled += cputime_to_nsecs(acct->utime_scaled);
if (acct->stime_scaled)
@@ -385,6 +392,7 @@ static void vtime_flush_scaled(struct task_struct *tsk,
acct->utime_scaled = 0;
acct->utime_sspurr = 0;
acct->stime_scaled = 0;
+#endif
}

/*
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index c7324e8469ee..cb7d1ce029c6 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -2442,11 +2442,15 @@ static void dump_one_paca(int cpu)

DUMP(p, accounting.utime, "%#-*lx");
DUMP(p, accounting.stime, "%#-*lx");
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
DUMP(p, accounting.utime_scaled, "%#-*lx");
+#endif
DUMP(p, accounting.starttime, "%#-*lx");
DUMP(p, accounting.starttime_user, "%#-*lx");
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
DUMP(p, accounting.startspurr, "%#-*lx");
DUMP(p, accounting.utime_sspurr, "%#-*lx");
+#endif
DUMP(p, accounting.steal_time, "%#-*lx");
#undef DUMP

--
2.13.3
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