[PATCH 1/5] processor.h: introduce cpu_relax_yield

From: Christian Borntraeger
Date: Fri Oct 21 2016 - 07:59:55 EST

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For spinning loops people did often use barrier() or cpu_relax().
For most architectures cpu_relax and barrier are the same, but on
some architectures cpu_relax can add some latency. For example on s390
cpu_relax gives up the time slice to the hypervisor. On power cpu_relax
tries to give some of the CPU to the neighbor threads. To reduce the
latency another variant cpu_relax_lowlatency was introduced. Before this
is used in more and more places, lets revert the logic of provide a new
function cpu_relax_yield that can spend some time and for s390 yields
the guest CPU.

Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
arch/alpha/include/asm/processor.h | 1 +
arch/arc/include/asm/processor.h | 2 ++
arch/arm/include/asm/processor.h | 1 +
arch/arm64/include/asm/processor.h | 1 +
arch/avr32/include/asm/processor.h | 1 +
arch/blackfin/include/asm/processor.h | 1 +
arch/c6x/include/asm/processor.h | 1 +
arch/cris/include/asm/processor.h | 1 +
arch/frv/include/asm/processor.h | 1 +
arch/h8300/include/asm/processor.h | 1 +
arch/hexagon/include/asm/processor.h | 1 +
arch/ia64/include/asm/processor.h | 1 +
arch/m32r/include/asm/processor.h | 1 +
arch/m68k/include/asm/processor.h | 1 +
arch/metag/include/asm/processor.h | 1 +
arch/microblaze/include/asm/processor.h | 1 +
arch/mips/include/asm/processor.h | 1 +
arch/mn10300/include/asm/processor.h | 1 +
arch/nios2/include/asm/processor.h | 1 +
arch/openrisc/include/asm/processor.h | 1 +
arch/parisc/include/asm/processor.h | 1 +
arch/powerpc/include/asm/processor.h | 1 +
arch/s390/include/asm/processor.h | 3 ++-
arch/s390/kernel/processor.c | 4 ++--
arch/score/include/asm/processor.h | 1 +
arch/sh/include/asm/processor.h | 1 +
arch/sparc/include/asm/processor_32.h | 1 +
arch/sparc/include/asm/processor_64.h | 1 +
arch/tile/include/asm/processor.h | 1 +
arch/unicore32/include/asm/processor.h | 1 +
arch/x86/include/asm/processor.h | 1 +
arch/xtensa/include/asm/processor.h | 1 +
32 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/arch/alpha/include/asm/processor.h b/arch/alpha/include/asm/processor.h
index 43a7559..0556fda 100644
--- a/arch/alpha/include/asm/processor.h
+++ b/arch/alpha/include/asm/processor.h
@@ -58,6 +58,7 @@ unsigned long get_wchan(struct task_struct *p);
((tsk) == current ? rdusp() : task_thread_info(tsk)->pcb.usp)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#define ARCH_HAS_PREFETCH
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index 16b630f..6c158d5 100644
--- a/arch/arc/include/asm/processor.h
+++ b/arch/arc/include/asm/processor.h
@@ -60,6 +60,7 @@ struct task_struct;
#ifndef CONFIG_EZNPS_MTM_EXT

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#else
@@ -67,6 +68,7 @@ struct task_struct;
#define cpu_relax() \
__asm__ __volatile__ (".word %0" : : "i"(CTOP_INST_SCHD_RW) : "memory")

+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() barrier()

#endif
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 8a1e8e9..db660e0 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -82,6 +82,7 @@ unsigned long get_wchan(struct task_struct *p);
#define cpu_relax() barrier()
#endif

+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#define task_pt_regs(p) \
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index df2e53d..797ee20 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -149,6 +149,7 @@ static inline void cpu_relax(void)
asm volatile("yield" ::: "memory");
}

+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Thread switching */
diff --git a/arch/avr32/include/asm/processor.h b/arch/avr32/include/asm/processor.h
index 941593c..e412e8b 100644
--- a/arch/avr32/include/asm/processor.h
+++ b/arch/avr32/include/asm/processor.h
@@ -92,6 +92,7 @@ extern struct avr32_cpuinfo boot_cpu_data;
#define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 3))

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()
#define cpu_sync_pipeline() asm volatile("sub pc, -2" : : : "memory")

diff --git a/arch/blackfin/include/asm/processor.h b/arch/blackfin/include/asm/processor.h
index 0c265ab..8b8704a 100644
--- a/arch/blackfin/include/asm/processor.h
+++ b/arch/blackfin/include/asm/processor.h
@@ -92,6 +92,7 @@ unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) ((tsk) == current ? rdusp() : (tsk)->thread.usp)

#define cpu_relax() smp_mb()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Get the Silicon Revision of the chip */
diff --git a/arch/c6x/include/asm/processor.h b/arch/c6x/include/asm/processor.h
index f2ef31b..914d730 100644
--- a/arch/c6x/include/asm/processor.h
+++ b/arch/c6x/include/asm/processor.h
@@ -121,6 +121,7 @@ extern unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(task) (task_pt_regs(task)->sp)

#define cpu_relax() do { } while (0)
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

extern const struct seq_operations cpuinfo_op;
diff --git a/arch/cris/include/asm/processor.h b/arch/cris/include/asm/processor.h
index 862126b..01dd52e 100644
--- a/arch/cris/include/asm/processor.h
+++ b/arch/cris/include/asm/processor.h
@@ -63,6 +63,7 @@ static inline void release_thread(struct task_struct *dead_task)
#define init_stack (init_thread_union.stack)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

void default_idle(void);
diff --git a/arch/frv/include/asm/processor.h b/arch/frv/include/asm/processor.h
index 73f0a79..4d00d65 100644
--- a/arch/frv/include/asm/processor.h
+++ b/arch/frv/include/asm/processor.h
@@ -107,6 +107,7 @@ unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) ((tsk)->thread.frame0->sp)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* data cache prefetch */
diff --git a/arch/h8300/include/asm/processor.h b/arch/h8300/include/asm/processor.h
index 111df73..683a061 100644
--- a/arch/h8300/include/asm/processor.h
+++ b/arch/h8300/include/asm/processor.h
@@ -127,6 +127,7 @@ unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) ((tsk) == current ? rdusp() : (tsk)->thread.usp)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#define HARD_RESET_NOW() ({ \
diff --git a/arch/hexagon/include/asm/processor.h b/arch/hexagon/include/asm/processor.h
index d850113..1558ddb 100644
--- a/arch/hexagon/include/asm/processor.h
+++ b/arch/hexagon/include/asm/processor.h
@@ -56,6 +56,7 @@ struct thread_struct {
}

#define cpu_relax() __vmyield()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/*
diff --git a/arch/ia64/include/asm/processor.h b/arch/ia64/include/asm/processor.h
index ce53c50..4654b71 100644
--- a/arch/ia64/include/asm/processor.h
+++ b/arch/ia64/include/asm/processor.h
@@ -547,6 +547,7 @@ ia64_eoi (void)
}

#define cpu_relax() ia64_hint(ia64_hint_pause)
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

static inline int
diff --git a/arch/m32r/include/asm/processor.h b/arch/m32r/include/asm/processor.h
index 9f8fd9b..b262037 100644
--- a/arch/m32r/include/asm/processor.h
+++ b/arch/m32r/include/asm/processor.h
@@ -133,6 +133,7 @@ unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) ((tsk)->thread.sp)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#endif /* _ASM_M32R_PROCESSOR_H */
diff --git a/arch/m68k/include/asm/processor.h b/arch/m68k/include/asm/processor.h
index c84a218..13e07ae 100644
--- a/arch/m68k/include/asm/processor.h
+++ b/arch/m68k/include/asm/processor.h
@@ -156,6 +156,7 @@ unsigned long get_wchan(struct task_struct *p);
#define task_pt_regs(tsk) ((struct pt_regs *) ((tsk)->thread.esp0))

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#endif
diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h
index a0333eb..61d6e27 100644
--- a/arch/metag/include/asm/processor.h
+++ b/arch/metag/include/asm/processor.h
@@ -152,6 +152,7 @@ unsigned long get_wchan(struct task_struct *p);
#define user_stack_pointer(regs) ((regs)->ctx.AX[0].U0)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

extern void setup_priv(void);
diff --git a/arch/microblaze/include/asm/processor.h b/arch/microblaze/include/asm/processor.h
index c38d0dd..fd7dd11 100644
--- a/arch/microblaze/include/asm/processor.h
+++ b/arch/microblaze/include/asm/processor.h
@@ -22,6 +22,7 @@
extern const struct seq_operations cpuinfo_op;

# define cpu_relax() barrier()
+# define cpu_relax_yield() cpu_relax()
# define cpu_relax_lowlatency() cpu_relax()

#define task_pt_regs(tsk) \
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index 0d36c87..9a656f6 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -389,6 +389,7 @@ unsigned long get_wchan(struct task_struct *p);
#define KSTK_STATUS(tsk) (task_pt_regs(tsk)->cp0_status)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/*
diff --git a/arch/mn10300/include/asm/processor.h b/arch/mn10300/include/asm/processor.h
index b10ba12..89f63d1 100644
--- a/arch/mn10300/include/asm/processor.h
+++ b/arch/mn10300/include/asm/processor.h
@@ -69,6 +69,7 @@ extern void print_cpu_info(struct mn10300_cpuinfo *);
extern void dodgy_tsc(void);

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/*
diff --git a/arch/nios2/include/asm/processor.h b/arch/nios2/include/asm/processor.h
index 1c953f0..303e593 100644
--- a/arch/nios2/include/asm/processor.h
+++ b/arch/nios2/include/asm/processor.h
@@ -88,6 +88,7 @@ extern unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) ((tsk)->thread.kregs->sp)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#endif /* __ASSEMBLY__ */
diff --git a/arch/openrisc/include/asm/processor.h b/arch/openrisc/include/asm/processor.h
index 70334c9..6ecfc2a 100644
--- a/arch/openrisc/include/asm/processor.h
+++ b/arch/openrisc/include/asm/processor.h
@@ -92,6 +92,7 @@ extern unsigned long thread_saved_pc(struct task_struct *t);
#define init_stack (init_thread_union.stack)

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#endif /* __ASSEMBLY__ */
diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index 2e674e1..ea2ff9f 100644
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -309,6 +309,7 @@ extern unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) ((tsk)->thread.regs.gr[30])

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/*
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index c07c31b..908fa7c 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -404,6 +404,7 @@ static inline unsigned long __pack_fe01(unsigned int fpmode)
#define cpu_relax() barrier()
#endif

+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Check that a certain kernel stack pointer is valid in task_struct p */
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 0332317..d05965b 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -234,8 +234,9 @@ static inline unsigned short stap(void)
/*
* Give up the time slice of the virtual PU.
*/
-void cpu_relax(void);
+void cpu_relax_yield(void);

+#define cpu_relax() cpu_relax_yield()
#define cpu_relax_lowlatency() barrier()

#define ECAG_CACHE_ATTRIBUTE 0
diff --git a/arch/s390/kernel/processor.c b/arch/s390/kernel/processor.c
index 81d0808..9e60ef1 100644
--- a/arch/s390/kernel/processor.c
+++ b/arch/s390/kernel/processor.c
@@ -53,7 +53,7 @@ void s390_update_cpu_mhz(void)
on_each_cpu(update_cpu_mhz, NULL, 0);
}

-void notrace cpu_relax(void)
+void notrace cpu_relax_yield(void)
{
if (!smp_cpu_mtid && MACHINE_HAS_DIAG44) {
diag_stat_inc(DIAG_STAT_X044);
@@ -61,7 +61,7 @@ void notrace cpu_relax(void)
}
barrier();
}
-EXPORT_SYMBOL(cpu_relax);
+EXPORT_SYMBOL(cpu_relax_yield);

/*
* cpu_init - initializes state that is per-CPU.
diff --git a/arch/score/include/asm/processor.h b/arch/score/include/asm/processor.h
index 851f441..e8e87b4 100644
--- a/arch/score/include/asm/processor.h
+++ b/arch/score/include/asm/processor.h
@@ -24,6 +24,7 @@ extern unsigned long get_wchan(struct task_struct *p);
#define current_text_addr() ({ __label__ _l; _l: &&_l; })

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()
#define release_thread(thread) do {} while (0)

diff --git a/arch/sh/include/asm/processor.h b/arch/sh/include/asm/processor.h
index f9a0994..099a991 100644
--- a/arch/sh/include/asm/processor.h
+++ b/arch/sh/include/asm/processor.h
@@ -97,6 +97,7 @@ extern struct sh_cpuinfo cpu_data[];

#define cpu_sleep() __asm__ __volatile__ ("sleep" : : : "memory")
#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

void default_idle(void);
diff --git a/arch/sparc/include/asm/processor_32.h b/arch/sparc/include/asm/processor_32.h
index 812fd08..50e908a3c 100644
--- a/arch/sparc/include/asm/processor_32.h
+++ b/arch/sparc/include/asm/processor_32.h
@@ -119,6 +119,7 @@ extern struct task_struct *last_task_used_math;
int do_mathemu(struct pt_regs *regs, struct task_struct *fpt);

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

extern void (*sparc_idle)(void);
diff --git a/arch/sparc/include/asm/processor_64.h b/arch/sparc/include/asm/processor_64.h
index ce2595c..3e8fac7 100644
--- a/arch/sparc/include/asm/processor_64.h
+++ b/arch/sparc/include/asm/processor_64.h
@@ -216,6 +216,7 @@ unsigned long get_wchan(struct task_struct *task);
"nop\n\t" \
".previous" \
::: "memory")
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Prefetch support. This is tuned for UltraSPARC-III and later.
diff --git a/arch/tile/include/asm/processor.h b/arch/tile/include/asm/processor.h
index 0684e88..91a39a5 100644
--- a/arch/tile/include/asm/processor.h
+++ b/arch/tile/include/asm/processor.h
@@ -264,6 +264,7 @@ static inline void cpu_relax(void)
barrier();
}

+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Info on this processor (see fs/proc/cpuinfo.c) */
diff --git a/arch/unicore32/include/asm/processor.h b/arch/unicore32/include/asm/processor.h
index 8d21b7a..fc54d5d 100644
--- a/arch/unicore32/include/asm/processor.h
+++ b/arch/unicore32/include/asm/processor.h
@@ -71,6 +71,7 @@ extern void release_thread(struct task_struct *);
unsigned long get_wchan(struct task_struct *p);

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

#define task_pt_regs(p) \
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 984a7bf..44adada 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -588,6 +588,7 @@ static __always_inline void cpu_relax(void)
rep_nop();
}

+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Stop speculative execution and prefetching of modified code. */
diff --git a/arch/xtensa/include/asm/processor.h b/arch/xtensa/include/asm/processor.h
index b42d68b..fe14dc2 100644
--- a/arch/xtensa/include/asm/processor.h
+++ b/arch/xtensa/include/asm/processor.h
@@ -206,6 +206,7 @@ extern unsigned long get_wchan(struct task_struct *p);
#define KSTK_ESP(tsk) (task_pt_regs(tsk)->areg[1])

#define cpu_relax() barrier()
+#define cpu_relax_yield() cpu_relax()
#define cpu_relax_lowlatency() cpu_relax()

/* Special register access. */
--
2.5.5

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