The patch titled
optimize and simplify get_cycles_sync()
has been added to the -mm tree. Its filename is
optimize-and-simplify-get_cycles_sync.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: optimize and simplify get_cycles_sync()
From: Joerg Roedel <joerg.roedel@xxxxxxx>
This patch simplifies the get_cycles_sync() function by removing the #ifdefs
from it. Further it introduces an optimization for AMD processors. There the
RDTSCP instruction is used instead of CPUID;RDTSC which is helpfull if the
kernel runs as a KVM guest. Running as a guest makes CPUID very expensive
because it causes an intercept of the guest.
Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/asm-i386/cpufeature.h | 1 +
include/asm-x86_64/tsc.h | 21 +++++++--------------
2 files changed, 8 insertions(+), 14 deletions(-)
diff -puN include/asm-i386/cpufeature.h~optimize-and-simplify-get_cycles_sync include/asm-i386/cpufeature.h
--- a/include/asm-i386/cpufeature.h~optimize-and-simplify-get_cycles_sync
+++ a/include/asm-i386/cpufeature.h
@@ -49,6 +49,7 @@
#define X86_FEATURE_MP (1*32+19) /* MP Capable. */
#define X86_FEATURE_NX (1*32+20) /* Execute Disable */
#define X86_FEATURE_MMXEXT (1*32+22) /* AMD MMX extensions */
+#define X86_FEATURE_RDTSCP (1*32+27) /* RDTSCP */
#define X86_FEATURE_LM (1*32+29) /* Long Mode (x86-64) */
#define X86_FEATURE_3DNOWEXT (1*32+30) /* AMD 3DNow! extensions */
#define X86_FEATURE_3DNOW (1*32+31) /* 3DNow! */
diff -puN include/asm-x86_64/tsc.h~optimize-and-simplify-get_cycles_sync include/asm-x86_64/tsc.h
--- a/include/asm-x86_64/tsc.h~optimize-and-simplify-get_cycles_sync
+++ a/include/asm-x86_64/tsc.h
@@ -34,22 +34,15 @@ static inline cycles_t get_cycles(void)
/* Like get_cycles, but make sure the CPU is synchronized. */
static __always_inline cycles_t get_cycles_sync(void)
{
- unsigned long long ret;
-#ifdef X86_FEATURE_SYNC_RDTSC
- unsigned eax;
+ unsigned int a, d;
- /*
- * Don't do an additional sync on CPUs where we know
- * RDTSC is already synchronous:
- */
- alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
- "=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
-#else
- sync_core();
-#endif
- rdtscll(ret);
+ alternative_io_two("cpuid\nrdtsc",
+ "rdtsc", X86_FEATURE_SYNC_RDTSC,
+ "rdtscp", X86_FEATURE_RDTSCP,
+ ASM_OUTPUT2("=a" (a), "=d" (d)),
+ "0" (1) : "ecx", "memory");
- return ret;
+ return ((unsigned long long)a) | (((unsigned long long)d)<<32);
}
extern void tsc_init(void);
_
Patches currently in -mm which might be from joerg.roedel@xxxxxxx are
git-kvm.patch
remove-constant_tsc-reporting-from-proc-cpuinfo-power.patch
i386-extend-alternative-instructions-framework.patch
x86_64-changes-to-x86_64-architecture-for.patch
i386-add-the-x86_feature_sync_rdtsc-flag.patch
optimize-and-simplify-get_cycles_sync.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
