[RFC/PATCH,4/5] cputime: use do_div() for nsec resolution conversion helpers

Commit Message

Kevin Hilman Feb. 21, 2013, 7:21 p.m. UTC

Namhyung Kim <[e-mail]> writes:

> Hi Kevin,
>
> On Wed, Feb 20, 2013 at 11:41:41AM -0800, Kevin Hilman wrote:
>> For the nsec resolution conversions to be useful on non 64-bit
>> architectures, do_div() needs to be used for the 64-bit divisions.
>> 
>> Signed-off-by: Kevin Hilman <[e-mail]>
>> ---
>>  include/asm-generic/cputime_nsecs.h | 51 +++++++++++++++++++++++++++----------
>>  1 file changed, 37 insertions(+), 14 deletions(-)
>> 
>> diff --git a/include/asm-generic/cputime_nsecs.h b/include/asm-generic/cputime_nsecs.h
>> index b6485ca..daa6075 100644
>> --- a/include/asm-generic/cputime_nsecs.h
>> +++ b/include/asm-generic/cputime_nsecs.h
>> @@ -24,13 +24,17 @@ typedef u64 __nocast cputime64_t;
>>  /*
>>   * Convert cputime <-> jiffies (HZ)
>>   */
>> -#define cputime_to_jiffies(__ct)	\
>> -	((__force u64)(__ct) / (NSEC_PER_SEC / HZ))
>> +static inline u64 cputime_to_jiffies(const cputime_t ct)
>> +{
>> +	cputime_t __ct = ct;
>
> Why it removed the "(__force u64)" conversion part?  Shouldn't it be:
>
> 	u64 __ct = (__force u64) ct;
>
> ?

You're right, that was an oversight.  Updated patch below.

Frederic, if you merge this, please take the one below with the __force
attributes added back.

I've updated my branch to include the fixed version.

Kevin


From a8a0a8b8b12512a7f862ade459cd88d2b48e2bf3 Mon Sep 17 00:00:00 2001
From: Kevin Hilman <[e-mail]>
Date: Thu, 14 Feb 2013 11:27:36 -0800
Subject: [PATCH 4/5] cputime: use do_div() for nsec resolution conversion
 helpers

For the nsec resolution conversions to be useful on non 64-bit
architectures, do_div() needs to be used for the 64-bit divisions.

Special thanks to Namhyung Kim for pointing out omissions of the
__force attribute in an earlier version.

Cc: Namhyung Kim <[e-mail]>
Signed-off-by: Kevin Hilman <[e-mail]>
---
 include/asm-generic/cputime_nsecs.h | 51 +++++++++++++++++++++++++++----------
 1 file changed, 37 insertions(+), 14 deletions(-)

Comments

Frederic Weisbecker Feb. 26, 2013, 3:21 p.m. UTC | #1

2013/2/21 Kevin Hilman <[e-mail]>:
> From a8a0a8b8b12512a7f862ade459cd88d2b48e2bf3 Mon Sep 17 00:00:00 2001
> From: Kevin Hilman <[e-mail]>
> Date: Thu, 14 Feb 2013 11:27:36 -0800
> Subject: [PATCH 4/5] cputime: use do_div() for nsec resolution conversion
>  helpers
>
> For the nsec resolution conversions to be useful on non 64-bit
> architectures, do_div() needs to be used for the 64-bit divisions.
>
> Special thanks to Namhyung Kim for pointing out omissions of the
> __force attribute in an earlier version.
>
> Cc: Namhyung Kim <[e-mail]>
> Signed-off-by: Kevin Hilman <[e-mail]>
> ---
>  include/asm-generic/cputime_nsecs.h | 51 +++++++++++++++++++++++++++----------
>  1 file changed, 37 insertions(+), 14 deletions(-)
>
> diff --git a/include/asm-generic/cputime_nsecs.h b/include/asm-generic/cputime_nsecs.h
> index b6485ca..d4944c9 100644
> --- a/include/asm-generic/cputime_nsecs.h
> +++ b/include/asm-generic/cputime_nsecs.h
> @@ -24,13 +24,17 @@ typedef u64 __nocast cputime64_t;
>  /*
>   * Convert cputime <-> jiffies (HZ)
>   */
> -#define cputime_to_jiffies(__ct)       \
> -       ((__force u64)(__ct) / (NSEC_PER_SEC / HZ))
> +static inline u64 cputime_to_jiffies(const cputime_t ct)
> +{
> +       u64 __ct = (__force u64) ct;
> +
> +       do_div(__ct, NSEC_PER_SEC / HZ);

So, when you don't need the remainder, could you please rather use
div_u64() ? It defaults to use do_div() anyway if the arch doesn't
override it. And none does apparently yet. But at least it paves the
way for further optimizations. And you can directly return the result.

Also, how about:

#define cputime_div(cputime, divisor)  div_u64((__force u64)cputime, divisor)

Thanks.

Patch

diff --git a/include/asm-generic/cputime_nsecs.h b/include/asm-generic/cputime_nsecs.h
index b6485ca..d4944c9 100644
--- a/include/asm-generic/cputime_nsecs.h
+++ b/include/asm-generic/cputime_nsecs.h
@@ -24,13 +24,17 @@  typedef u64 __nocast cputime64_t;
 /*
  * Convert cputime <-> jiffies (HZ)
  */
-#define cputime_to_jiffies(__ct)	\
-	((__force u64)(__ct) / (NSEC_PER_SEC / HZ))
+static inline u64 cputime_to_jiffies(const cputime_t ct)
+{
+	u64 __ct = (__force u64) ct;
+
+	do_div(__ct, NSEC_PER_SEC / HZ);
+	return __ct;
+}
 #define cputime_to_scaled(__ct)		(__ct)
 #define jiffies_to_cputime(__jif)	\
 	(__force cputime_t)((__jif) * (NSEC_PER_SEC / HZ))
-#define cputime64_to_jiffies64(__ct)	\
-	((__force u64)(__ct) / (NSEC_PER_SEC / HZ))
+#define cputime64_to_jiffies64(__ct) cputime_to_jiffies(__ct)
 #define jiffies64_to_cputime64(__jif)	\
 	(__force cputime64_t)((__jif) * (NSEC_PER_SEC / HZ))
 
@@ -44,8 +48,13 @@  typedef u64 __nocast cputime64_t;
 /*
  * Convert cputime <-> microseconds
  */
-#define cputime_to_usecs(__ct)		\
-	((__force u64)(__ct) / NSEC_PER_USEC)
+static inline u64 cputime_to_usecs(const cputime_t ct)
+{
+	u64 __ct = (__force u64) ct;
+
+	do_div(__ct, NSEC_PER_USEC);
+	return __ct;
+}
 #define usecs_to_cputime(__usecs)	\
 	(__force cputime_t)((__usecs) * NSEC_PER_USEC)
 #define usecs_to_cputime64(__usecs)	\
@@ -54,8 +63,13 @@  typedef u64 __nocast cputime64_t;
 /*
  * Convert cputime <-> seconds
  */
-#define cputime_to_secs(__ct)		\
-	((__force u64)(__ct) / NSEC_PER_SEC)
+static inline u64 cputime_to_secs(const cputime_t ct)
+{
+	u64 __ct = (__force u64) ct;
+
+	do_div(__ct, NSEC_PER_SEC);
+	return __ct;
+}
 #define secs_to_cputime(__secs)		\
 	(__force cputime_t)((__secs) * NSEC_PER_SEC)
 
@@ -69,8 +83,10 @@  static inline cputime_t timespec_to_cputime(const struct timespec *val)
 }
 static inline void cputime_to_timespec(const cputime_t ct, struct timespec *val)
 {
-	val->tv_sec  = (__force u64) ct / NSEC_PER_SEC;
-	val->tv_nsec = (__force u64) ct % NSEC_PER_SEC;
+	u64 __ct = (__force u64) ct;
+
+	val->tv_nsec = do_div(__ct, NSEC_PER_SEC);
+	val->tv_sec = __ct;
 }
 
 /*
@@ -83,15 +99,22 @@  static inline cputime_t timeval_to_cputime(struct timeval *val)
 }
 static inline void cputime_to_timeval(const cputime_t ct, struct timeval *val)
 {
-	val->tv_sec = (__force u64) ct / NSEC_PER_SEC;
-	val->tv_usec = ((__force u64) ct % NSEC_PER_SEC) / NSEC_PER_USEC;
+	u64 __ct = (__force u64) ct;
+
+	val->tv_usec = do_div(__ct, NSEC_PER_SEC) / NSEC_PER_USEC;
+	val->tv_sec = __ct;
 }
 
 /*
  * Convert cputime <-> clock (USER_HZ)
  */
-#define cputime_to_clock_t(__ct)	\
-	((__force u64)(__ct) / (NSEC_PER_SEC / USER_HZ))
+static inline u64 cputime_to_clock_t(const cputime_t ct)
+{
+	u64 __ct = (__force u64) ct;
+
+	do_div(__ct, (NSEC_PER_SEC / USER_HZ));
+	return __ct;
+}
 #define clock_t_to_cputime(__x)		\
 	(__force cputime_t)((__x) * (NSEC_PER_SEC / USER_HZ))