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| author | Anton Blanchard <anton@samba.org> | 2014-07-03 15:52:03 +1000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2014-07-11 16:05:58 +1000 |
| commit | cc1adb5f32557f10f48e8febbef7278a2db9d593 (patch) | |
| tree | f1570219053c85fa3db71e123af26f5776c16dd5 /arch/powerpc/platforms/pseries/lpar.c | |
| parent | 8fa5d4547eb69b7ed710cb03486d33a3a5dc2ead (diff) | |
| download | linux-cc1adb5f32557f10f48e8febbef7278a2db9d593.tar.gz | |
powerpc/pseries: Use jump labels for hcall tracepoints
hcall tracepoints add quite a few instructions to our hcall path:
plpar_hcall:
mr r2,r2
mfcr r0
stw r0,8(r1)
b 164 <---- start
ld r12,0(r2)
std r12,32(r1)
cmpdi r12,0
beq 164 <---- end
...
We have an unconditional branch that gets noped out during boot and
a load/compare/branch. We also store the tracepoint value to the
stack for the hcall_exit path to use.
By using jump labels we can simplify this to just a single nop that
gets replaced with a branch when the tracepoint is enabled:
plpar_hcall:
mr r2,r2
mfcr r0
stw r0,8(r1)
nop <----
...
If jump labels are not enabled, we fall back to the old method.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/platforms/pseries/lpar.c')
| -rw-r--r-- | arch/powerpc/platforms/pseries/lpar.c | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index b02af9ef3ff61..fbfcef514aa74 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -26,6 +26,7 @@ #include <linux/dma-mapping.h> #include <linux/console.h> #include <linux/export.h> +#include <linux/static_key.h> #include <asm/processor.h> #include <asm/mmu.h> #include <asm/page.h> @@ -649,6 +650,19 @@ EXPORT_SYMBOL(arch_free_page); #endif #ifdef CONFIG_TRACEPOINTS +#ifdef CONFIG_JUMP_LABEL +struct static_key hcall_tracepoint_key = STATIC_KEY_INIT; + +void hcall_tracepoint_regfunc(void) +{ + static_key_slow_inc(&hcall_tracepoint_key); +} + +void hcall_tracepoint_unregfunc(void) +{ + static_key_slow_dec(&hcall_tracepoint_key); +} +#else /* * We optimise our hcall path by placing hcall_tracepoint_refcount * directly in the TOC so we can check if the hcall tracepoints are @@ -658,13 +672,6 @@ EXPORT_SYMBOL(arch_free_page); /* NB: reg/unreg are called while guarded with the tracepoints_mutex */ extern long hcall_tracepoint_refcount; -/* - * Since the tracing code might execute hcalls we need to guard against - * recursion. One example of this are spinlocks calling H_YIELD on - * shared processor partitions. - */ -static DEFINE_PER_CPU(unsigned int, hcall_trace_depth); - void hcall_tracepoint_regfunc(void) { hcall_tracepoint_refcount++; @@ -674,6 +681,15 @@ void hcall_tracepoint_unregfunc(void) { hcall_tracepoint_refcount--; } +#endif + +/* + * Since the tracing code might execute hcalls we need to guard against + * recursion. One example of this are spinlocks calling H_YIELD on + * shared processor partitions. + */ +static DEFINE_PER_CPU(unsigned int, hcall_trace_depth); + void __trace_hcall_entry(unsigned long opcode, unsigned long *args) { |