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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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abcff86df2
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>
70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
/*
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* Definitions for measuring cputime on powerpc machines.
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*
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* Copyright (C) 2006 Paul Mackerras, IBM Corp.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* If we have CONFIG_VIRT_CPU_ACCOUNTING_NATIVE, we measure cpu time in
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* the same units as the timebase. Otherwise we measure cpu time
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* in jiffies using the generic definitions.
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*/
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#ifndef __POWERPC_CPUTIME_H
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#define __POWERPC_CPUTIME_H
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
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#include <linux/types.h>
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#include <linux/time.h>
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#include <asm/div64.h>
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#include <asm/time.h>
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#include <asm/param.h>
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typedef u64 __nocast cputime_t;
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typedef u64 __nocast cputime64_t;
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#define cmpxchg_cputime(ptr, old, new) cmpxchg(ptr, old, new)
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#ifdef __KERNEL__
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/*
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* Convert cputime <-> microseconds
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*/
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extern u64 __cputime_usec_factor;
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static inline unsigned long cputime_to_usecs(const cputime_t ct)
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{
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return mulhdu((__force u64) ct, __cputime_usec_factor);
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}
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/*
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* PPC64 uses PACA which is task independent for storing accounting data while
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* PPC32 uses struct thread_info, therefore at task switch the accounting data
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* has to be populated in the new task
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*/
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#ifdef CONFIG_PPC64
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#define get_accounting(tsk) (&get_paca()->accounting)
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static inline void arch_vtime_task_switch(struct task_struct *tsk) { }
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#else
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#define get_accounting(tsk) (&task_thread_info(tsk)->accounting)
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/*
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* Called from the context switch with interrupts disabled, to charge all
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* accumulated times to the current process, and to prepare accounting on
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* the next process.
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*/
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static inline void arch_vtime_task_switch(struct task_struct *prev)
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{
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struct cpu_accounting_data *acct = get_accounting(current);
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struct cpu_accounting_data *acct0 = get_accounting(prev);
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acct->starttime = acct0->starttime;
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}
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#endif
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#endif /* __KERNEL__ */
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#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
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#endif /* __POWERPC_CPUTIME_H */
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