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From: Jonathan Lim <jlim@sgi.com>
To: linux-kernel@vger.kernel.org
Cc: akpm@linux-foundation.org
Subject: [PATCH] Provide u64 version of jiffies_to_usecs() in kernel/tsacct.c
Date: Thu, 14 Feb 2008 18:27:52 -0800 (PST)	[thread overview]
Message-ID: <200802150227.m1F2RrSi174268@sabah.engr.sgi.com> (raw)

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.

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	Thu Feb 14 18:08:08 PST 2008
@@ -268,6 +268,12 @@ unsigned int inline jiffies_to_usecs(con
 }
 EXPORT_SYMBOL(jiffies_to_usecs);
 
+u64 jiffies_64_to_usecs(const u64 j)
+{
+	return (j*HZ_TO_USEC_NUM + HZ_TO_USEC_DEN-1) / HZ_TO_USEC_DEN;
+}
+EXPORT_SYMBOL(jiffies_64_to_usecs);
+
 /**
  * timespec_trunc - Truncate timespec to a granularity
  * @t: Timespec
--- 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 */

             reply	other threads:[~2008-02-15  2:27 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-15  2:27 Jonathan Lim [this message]
     [not found] <no.id>
2008-01-08  1:04 ` Jonathan Lim
2008-02-19 20:52 ` Jonathan Lim
2008-02-19 21:25   ` Randy Dunlap
2008-02-20  2:17     ` Jonathan Lim
2008-02-20  3:52       ` Randy Dunlap
2008-02-25 22:27 ` Jonathan Lim
2008-03-12 23:53   ` Roman Zippel
2008-04-18 21:54 ` Jonathan Lim
     [not found] <200801022103.m02L3oL1051764@sabah.engr.sgi.com>
2008-01-03  0:23 ` Andrew Morton
2008-01-03  0:36   ` H. Peter Anvin
2008-01-03  1:06     ` Jonathan Lim
2008-01-03  1:13       ` H. Peter Anvin
  -- strict thread matches above, loose matches on Subject: below --
2007-12-28 21:26 Jonathan Lim
2007-12-29  4:52 ` H. Peter Anvin

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