Don't do load-average calculations at even 5-second intervals

It turns out that there are a few other five-second timers in the
kernel, and if the timers get in sync, the load-average can get
artificially inflated by events that just happen to coincide.

So just offset the load average calculation it by a timer tick.

Noticed by Anders Boström, for whom the coincidence started triggering
on one of his machines with the JBD jiffies rounding code (JBD is one of
the subsystems that also end up using a 5-second timer by default).

Tested-by: Anders Boström <anders@bostrom.dyndns.org>
Cc: Chuck Ebbert <cebbert@redhat.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index a01ac6d..313c6b6 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -113,7 +113,7 @@ extern unsigned long avenrun[];             /* Load averages */
 
 #define FSHIFT         11              /* nr of bits of precision */
 #define FIXED_1                (1<<FSHIFT)     /* 1.0 as fixed-point */
-#define LOAD_FREQ      (5*HZ)          /* 5 sec intervals */
+#define LOAD_FREQ      (5*HZ+1)        /* 5 sec intervals */
 #define EXP_1          1884            /* 1/exp(5sec/1min) as fixed-point */
 #define EXP_5          2014            /* 1/exp(5sec/5min) */
 #define EXP_15         2037            /* 1/exp(5sec/15min) */