Message ID | 1440183128-1384-3-git-send-email-christopher.s.hall@intel.com |
---|---|
State | Superseded |
Headers | show |
On Fri, 21 Aug 2015, Christopher S. Hall wrote: > Add detect_art() call to early TSC initialization which reads ART->TSC > numerator/denominator and sets CPU feature if present > > Add convert_art_to_tsc() function performing conversion ART to TSC > > Add art_timestamp referencing art_to_tsc() and clocksource_tsc enabling > driver conversion of ART to TSC That changelog needs a rewrite. See patch 1/4 > @@ -352,6 +352,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; > #define cpu_has_de boot_cpu_has(X86_FEATURE_DE) > #define cpu_has_pse boot_cpu_has(X86_FEATURE_PSE) > #define cpu_has_tsc boot_cpu_has(X86_FEATURE_TSC) > +#define cpu_has_art boot_cpu_has(X86_FEATURE_ART) Please do not add more cpu_has macros. There is nothing wrong to write boot_cpu_has(X86_FEATURE_ART) in the code. > +#define ART_CPUID_LEAF (0x15) > +#define ART_MIN_DENOMINATOR (2) #define ART_CPUID_LEAF 0x15 #define ART_MIN_DENOMINATOR 2 Why is the minimum denominator 2? That wants a comment. > +static u32 art_to_tsc_numerator; > +static u32 art_to_tsc_denominator; Both want to be read_mostly > +/* > + * If ART is present detect the numberator:denominator to convert to TSC > + */ > +void detect_art(void) > +{ > + unsigned int unused[2]; > + > + if (boot_cpu_data.cpuid_level >= ART_CPUID_LEAF) { > + cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator, > + &art_to_tsc_numerator, unused, unused+1); > + > + if (art_to_tsc_denominator >= ART_MIN_DENOMINATOR) { > + set_cpu_cap(&boot_cpu_data, X86_FEATURE_ART); > + } No parentheses around one liners please. > + } > +} > + > static int __init cpufreq_tsc(void) > { > if (!cpu_has_tsc) > return 0; > + > + detect_art(); > + > if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) > return 0; > cpufreq_register_notifier(&time_cpufreq_notifier_block, > @@ -1059,6 +1085,32 @@ int unsynchronized_tsc(void) > return 0; > } > > +/* > + * Convert ART to TSC given numerator/denominator found in detect_art() > + */ > +static u64 convert_art_to_tsc(struct correlated_cs *cs, u64 cycles) > +{ > + u64 tmp, res; > + > + switch (art_to_tsc_denominator) { > + default: > + res = (cycles / art_to_tsc_denominator) * art_to_tsc_numerator; > + tmp = (cycles % art_to_tsc_denominator) * art_to_tsc_numerator; > + res += tmp / art_to_tsc_denominator; > + break; > + case 2: > + res = (cycles >> 1) * art_to_tsc_numerator; > + tmp = (cycles & 0x1) * art_to_tsc_numerator; > + res += tmp >> 1; > + break; Is it really worth do do this optimization? And if we do it we shouldn't special case it for 2. You can check at ART detection time whether the denominator is a power of two and have a flag which selects a div/mod base or a shift based conversion. Thanks, tglx
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 3d6606f..a9322e5 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -85,7 +85,7 @@ #define X86_FEATURE_P4 ( 3*32+ 7) /* "" P4 */ #define X86_FEATURE_CONSTANT_TSC ( 3*32+ 8) /* TSC ticks at a constant rate */ #define X86_FEATURE_UP ( 3*32+ 9) /* smp kernel running on up */ -/* free, was #define X86_FEATURE_FXSAVE_LEAK ( 3*32+10) * "" FXSAVE leaks FOP/FIP/FOP */ +#define X86_FEATURE_ART (3*32+10) /* Platform has always running timer (ART) */ #define X86_FEATURE_ARCH_PERFMON ( 3*32+11) /* Intel Architectural PerfMon */ #define X86_FEATURE_PEBS ( 3*32+12) /* Precise-Event Based Sampling */ #define X86_FEATURE_BTS ( 3*32+13) /* Branch Trace Store */ @@ -352,6 +352,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define cpu_has_de boot_cpu_has(X86_FEATURE_DE) #define cpu_has_pse boot_cpu_has(X86_FEATURE_PSE) #define cpu_has_tsc boot_cpu_has(X86_FEATURE_TSC) +#define cpu_has_art boot_cpu_has(X86_FEATURE_ART) #define cpu_has_pge boot_cpu_has(X86_FEATURE_PGE) #define cpu_has_apic boot_cpu_has(X86_FEATURE_APIC) #define cpu_has_sep boot_cpu_has(X86_FEATURE_SEP) diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 94605c0..8d52d91 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -45,6 +45,8 @@ static __always_inline cycles_t vget_cycles(void) return (cycles_t)__native_read_tsc(); } +extern struct correlated_cs art_timestamper; + extern void tsc_init(void); extern void mark_tsc_unstable(char *reason); extern int unsynchronized_tsc(void); diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 7437b41..13f12e0 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -939,10 +939,36 @@ static struct notifier_block time_cpufreq_notifier_block = { .notifier_call = time_cpufreq_notifier }; +#define ART_CPUID_LEAF (0x15) +#define ART_MIN_DENOMINATOR (2) + +static u32 art_to_tsc_numerator; +static u32 art_to_tsc_denominator; + +/* + * If ART is present detect the numberator:denominator to convert to TSC + */ +void detect_art(void) +{ + unsigned int unused[2]; + + if (boot_cpu_data.cpuid_level >= ART_CPUID_LEAF) { + cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator, + &art_to_tsc_numerator, unused, unused+1); + + if (art_to_tsc_denominator >= ART_MIN_DENOMINATOR) { + set_cpu_cap(&boot_cpu_data, X86_FEATURE_ART); + } + } +} + static int __init cpufreq_tsc(void) { if (!cpu_has_tsc) return 0; + + detect_art(); + if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) return 0; cpufreq_register_notifier(&time_cpufreq_notifier_block, @@ -1059,6 +1085,32 @@ int unsynchronized_tsc(void) return 0; } +/* + * Convert ART to TSC given numerator/denominator found in detect_art() + */ +static u64 convert_art_to_tsc(struct correlated_cs *cs, u64 cycles) +{ + u64 tmp, res; + + switch (art_to_tsc_denominator) { + default: + res = (cycles / art_to_tsc_denominator) * art_to_tsc_numerator; + tmp = (cycles % art_to_tsc_denominator) * art_to_tsc_numerator; + res += tmp / art_to_tsc_denominator; + break; + case 2: + res = (cycles >> 1) * art_to_tsc_numerator; + tmp = (cycles & 0x1) * art_to_tsc_numerator; + res += tmp >> 1; + break; + } + return res; +} + +struct correlated_cs art_timestamper = { + .convert = convert_art_to_tsc, +}; +EXPORT_SYMBOL(art_timestamper); static void tsc_refine_calibration_work(struct work_struct *work); static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work); @@ -1130,6 +1182,8 @@ static void tsc_refine_calibration_work(struct work_struct *work) (unsigned long)tsc_khz % 1000); out: + if (cpu_has_art) + art_timestamper.related_cs = &clocksource_tsc; clocksource_register_khz(&clocksource_tsc, tsc_khz); }
Add detect_art() call to early TSC initialization which reads ART->TSC numerator/denominator and sets CPU feature if present Add convert_art_to_tsc() function performing conversion ART to TSC Add art_timestamp referencing art_to_tsc() and clocksource_tsc enabling driver conversion of ART to TSC Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com> --- arch/x86/include/asm/cpufeature.h | 3 ++- arch/x86/include/asm/tsc.h | 2 ++ arch/x86/kernel/tsc.c | 54 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 58 insertions(+), 1 deletion(-)