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| author | Christophe Leroy <christophe.leroy@c-s.fr> | 2018-08-02 09:53:59 +0200 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-10-20 04:26:47 +0200 |
| commit | abcff86df2d2ec0a0ca9470fa5d2a184af18928a (patch) | |
| tree | 75fa912a58d6371828a653a393d7b766d0d4649b /arch/powerpc/kernel | |
| parent | powerpc/time: isolate scaled cputime accounting in dedicated functions. (diff) | |
| download | linux-abcff86df2d2ec0a0ca9470fa5d2a184af18928a.tar.xz linux-abcff86df2d2ec0a0ca9470fa5d2a184af18928a.zip | |
powerpc/time: Only set CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC64
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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel')
| -rw-r--r-- | arch/powerpc/kernel/time.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index cf0d5c2834d0..9289fac75af7 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -176,7 +176,7 @@ 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); @@ -285,7 +285,8 @@ 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; @@ -316,6 +317,7 @@ static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct, } } acct->utime_scaled += utime_scaled; +#endif return stime_scaled; } @@ -352,7 +354,9 @@ 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; @@ -361,7 +365,9 @@ 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); @@ -378,6 +384,7 @@ 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) @@ -386,6 +393,7 @@ static void vtime_flush_scaled(struct task_struct *tsk, acct->utime_scaled = 0; acct->utime_sspurr = 0; acct->stime_scaled = 0; +#endif } /* |