Messages in this thread Patch in this message | | | From | Jonathan Lim <> | Subject | Re: [PATCH] Provide u64 version of jiffies_to_usecs() in kernel/tsacct.c | Date | Fri, 18 Apr 2008 14:54:30 -0700 (PDT) |
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It's possible that the values used in and returned from jiffies_to_usecs() are incorrect because of truncation when variables of type u64 are involved. So a function specific to that type is used instead.
This version implements a correction to jiffies_64_to_usecs() based on feedback from Randy Dunlap and Roman Zippel.
Diff'd against: linux/kernel/git/torvalds/linux-2.6.git
Signed-off-by: Jonathan Lim <jlim@sgi.com>
--- a/include/linux/jiffies.h Thu Feb 14 18:04:14 PST 2008 +++ b/include/linux/jiffies.h Thu Feb 14 18:07:17 PST 2008 @@ -42,7 +42,7 @@ /* LATCH is used in the interval timer and ftape setup. */ #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */ -/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, then we can +/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can * improve accuracy by shifting LSH bits, hence calculating: * (NOM << LSH) / DEN * This however means trouble for large NOM, because (NOM << LSH) may no @@ -204,7 +204,7 @@ extern unsigned long preset_lpj; * operator if the result is a long long AND at least one of the * operands is cast to long long (usually just prior to the "*" so as * not to confuse it into thinking it really has a 64-bit operand, - * which, buy the way, it can do, but it takes more code and at least 2 + * which, by the way, it can do, but it takes more code and at least 2 * mpys). * We also need to be aware that one second in nanoseconds is only a @@ -269,6 +269,7 @@ extern unsigned long preset_lpj; */ extern unsigned int jiffies_to_msecs(const unsigned long j); extern unsigned int jiffies_to_usecs(const unsigned long j); +extern u64 jiffies_64_to_usecs(const u64 j); extern unsigned long msecs_to_jiffies(const unsigned int m); extern unsigned long usecs_to_jiffies(const unsigned int u); extern unsigned long timespec_to_jiffies(const struct timespec *value); --- a/kernel/time.c Thu Feb 14 18:05:12 PST 2008 +++ b/kernel/time.c Fri Apr 18 14:44:54 PDT 2008 @@ -38,6 +38,7 @@ #include <asm/uaccess.h> #include <asm/unistd.h> +#include <asm/div64.h> #include "timeconst.h" @@ -267,6 +268,16 @@ unsigned int inline jiffies_to_usecs(con #endif } EXPORT_SYMBOL(jiffies_to_usecs); + +u64 jiffies_64_to_usecs(const u64 j) +{ +# if BITS_PER_LONG == 32 + return ((u64)HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; +# else + return div64_64(j*HZ_TO_USEC_NUM + HZ_TO_USEC_DEN-1, HZ_TO_USEC_DEN); +# endif +} +EXPORT_SYMBOL(jiffies_64_to_usecs); /** * timespec_trunc - Truncate timespec to a granularity --- a/kernel/tsacct.c Thu Feb 14 18:06:17 PST 2008 +++ b/kernel/tsacct.c Thu Feb 14 18:08:47 PST 2008 @@ -85,8 +85,8 @@ void xacct_add_tsk(struct taskstats *sta struct mm_struct *mm; /* convert pages-jiffies to Mbyte-usec */ - stats->coremem = jiffies_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB; - stats->virtmem = jiffies_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB; + stats->coremem = jiffies_64_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB; + stats->virtmem = jiffies_64_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB; mm = get_task_mm(p); if (mm) { /* adjust to KB unit */
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