Re: [PATCH] powerpc: fix wrong divisor in usecs_to_cputime
From: Anton Blanchard <hidden>
Date: 2011-12-09 23:28:37
Hi Andreas,
Commit d57af9b (taskstats: use real microsecond granularity for CPU times) renamed msecs_to_cputime to usecs_to_cputime, but failed to update all numbers on the way. This causes nonsensical cpu idle/iowait values to be displayed in /proc/stat (the only user of usecs_to_cputime so far). This also renames __cputime_msec_factor to __cputime_usec_factor, adapting its value and using it directly in cputime_to_usecs instead of doing two multiplications.
Thanks for finding this! I noticed the strange behaviour yesterday and was just about to investigate. Can I suggest we add: Cc: <redacted> [2.6.37+] so it will make it back into the stable trees? Anton
Signed-off-by: Andreas Schwab <redacted>
FWIW: Acked-by: Anton Blanchard <redacted>
quoted hunk ↗ jump to hunk
--- arch/powerpc/include/asm/cputime.h | 6 +++--- arch/powerpc/kernel/time.c | 10 +++++----- 2 files changed, 8 insertions(+), 8 deletions(-)diff --git a/arch/powerpc/include/asm/cputime.hb/arch/powerpc/include/asm/cputime.h index 1cf20bd..33a3580 100644--- a/arch/powerpc/include/asm/cputime.h +++ b/arch/powerpc/include/asm/cputime.h@@ -126,11 +126,11 @@ static inline u64 cputime64_to_jiffies64(constcputime_t ct) /* * Convert cputime <-> microseconds */ -extern u64 __cputime_msec_factor; +extern u64 __cputime_usec_factor; static inline unsigned long cputime_to_usecs(const cputime_t ct) { - return mulhdu(ct, __cputime_msec_factor) * USEC_PER_MSEC; + return mulhdu(ct, __cputime_usec_factor); } static inline cputime_t usecs_to_cputime(const unsigned long us)@@ -143,7 +143,7 @@ static inline cputime_t usecs_to_cputime(constunsigned long us) sec = us / 1000000; if (ct) { ct *= tb_ticks_per_sec; - do_div(ct, 1000); + do_div(ct, 1000000); } if (sec) ct += (cputime_t) sec * tb_ticks_per_sec;diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 522bb1d..69477e5 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c@@ -168,13 +168,13 @@ EXPORT_SYMBOL_GPL(ppc_tb_freq); #ifdef CONFIG_VIRT_CPU_ACCOUNTING /* * Factors for converting from cputime_t (timebase ticks) to - * jiffies, milliseconds, seconds, and clock_t (1/USER_HZ seconds). + * jiffies, microseconds, seconds, and clock_t (1/USER_HZ seconds). * These are all stored as 0.64 fixed-point binary fractions. */ u64 __cputime_jiffies_factor; EXPORT_SYMBOL(__cputime_jiffies_factor); -u64 __cputime_msec_factor; -EXPORT_SYMBOL(__cputime_msec_factor); +u64 __cputime_usec_factor; +EXPORT_SYMBOL(__cputime_usec_factor); u64 __cputime_sec_factor; EXPORT_SYMBOL(__cputime_sec_factor); u64 __cputime_clockt_factor;@@ -192,8 +192,8 @@ static void calc_cputime_factors(void) div128_by_32(HZ, 0, tb_ticks_per_sec, &res); __cputime_jiffies_factor = res.result_low; - div128_by_32(1000, 0, tb_ticks_per_sec, &res); - __cputime_msec_factor = res.result_low; + div128_by_32(1000000, 0, tb_ticks_per_sec, &res); + __cputime_usec_factor = res.result_low; div128_by_32(1, 0, tb_ticks_per_sec, &res); __cputime_sec_factor = res.result_low; div128_by_32(USER_HZ, 0, tb_ticks_per_sec, &res);