From 688340ea34c61ad12473ccd837325b59aada9a93 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 17 Jul 2007 18:37:04 -0700 Subject: Add a sched_clock paravirt_op The tsc-based get_scheduled_cycles interface is not a good match for Xen's runstate accounting, which reports everything in nanoseconds. This patch replaces this interface with a sched_clock interface, which matches both Xen and VMI's requirements. In order to do this, we: 1. replace get_scheduled_cycles with sched_clock 2. hoist cycles_2_ns into a common header 3. update vmi accordingly One thing to note: because sched_clock is implemented as a weak function in kernel/sched.c, we must define a real function in order to override this weak binding. This means the usual paravirt_ops technique of using an inline function won't work in this case. Signed-off-by: Jeremy Fitzhardinge Cc: Zachary Amsden Cc: Dan Hecht Cc: john stultz --- arch/i386/kernel/paravirt.c | 2 +- arch/i386/kernel/tsc.c | 23 +++++++++++++++-------- arch/i386/kernel/vmi.c | 2 +- arch/i386/kernel/vmiclock.c | 6 +++--- 4 files changed, 20 insertions(+), 13 deletions(-) (limited to 'arch/i386/kernel') diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c index 60e08b9b50a4..53f07a8275e3 100644 --- a/arch/i386/kernel/paravirt.c +++ b/arch/i386/kernel/paravirt.c @@ -302,7 +302,7 @@ struct paravirt_ops paravirt_ops = { .write_msr = native_write_msr_safe, .read_tsc = native_read_tsc, .read_pmc = native_read_pmc, - .get_scheduled_cycles = native_read_tsc, + .sched_clock = native_sched_clock, .get_cpu_khz = native_calculate_cpu_khz, .load_tr_desc = native_load_tr_desc, .set_ldt = native_set_ldt, diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index ea63a30ca3e8..252f9010f283 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -84,7 +84,7 @@ static inline int check_tsc_unstable(void) * * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ -static unsigned long cyc2ns_scale __read_mostly; +unsigned long cyc2ns_scale __read_mostly; #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ @@ -93,15 +93,10 @@ static inline void set_cyc2ns_scale(unsigned long cpu_khz) cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz; } -static inline unsigned long long cycles_2_ns(unsigned long long cyc) -{ - return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR; -} - /* * Scheduler clock - returns current time in nanosec units. */ -unsigned long long sched_clock(void) +unsigned long long native_sched_clock(void) { unsigned long long this_offset; @@ -118,12 +113,24 @@ unsigned long long sched_clock(void) return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); /* read the Time Stamp Counter: */ - get_scheduled_cycles(this_offset); + rdtscll(this_offset); /* return the value in ns */ return cycles_2_ns(this_offset); } +/* We need to define a real function for sched_clock, to override the + weak default version */ +#ifdef CONFIG_PARAVIRT +unsigned long long sched_clock(void) +{ + return paravirt_sched_clock(); +} +#else +unsigned long long sched_clock(void) + __attribute__((alias("native_sched_clock"))); +#endif + unsigned long native_calculate_cpu_khz(void) { unsigned long long start, end; diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c index 234bd6ff518d..72042bb7ec94 100644 --- a/arch/i386/kernel/vmi.c +++ b/arch/i386/kernel/vmi.c @@ -891,7 +891,7 @@ static inline int __init activate_vmi(void) paravirt_ops.setup_boot_clock = vmi_time_bsp_init; paravirt_ops.setup_secondary_clock = vmi_time_ap_init; #endif - paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles; + paravirt_ops.sched_clock = vmi_sched_clock; paravirt_ops.get_cpu_khz = vmi_cpu_khz; /* We have true wallclock functions; disable CMOS clock sync */ diff --git a/arch/i386/kernel/vmiclock.c b/arch/i386/kernel/vmiclock.c index 26a37f8a8762..f9b845f4e692 100644 --- a/arch/i386/kernel/vmiclock.c +++ b/arch/i386/kernel/vmiclock.c @@ -64,10 +64,10 @@ int vmi_set_wallclock(unsigned long now) return 0; } -/* paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles */ -unsigned long long vmi_get_sched_cycles(void) +/* paravirt_ops.sched_clock = vmi_sched_clock */ +unsigned long long vmi_sched_clock(void) { - return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_AVAILABLE); + return cycles_2_ns(vmi_timer_ops.get_cycle_counter(VMI_CYCLES_AVAILABLE)); } /* paravirt_ops.get_cpu_khz = vmi_cpu_khz */ -- cgit v1.2.2