From abcff86df2d2ec0a0ca9470fa5d2a184af18928a Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Thu, 2 Aug 2018 07:53:59 +0000 Subject: 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 Signed-off-by: Michael Ellerman --- arch/powerpc/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/powerpc/Kconfig') diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 076e05ae9b04..e84943d24e5c 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 -- cgit v1.2.3