Messages in this thread | | | From | Eric Dumazet <> | Subject | Re: [PATCH (update 3)] timer: Run calc_load halfway through each round_jiffies second | Date | Fri, 2 Mar 2007 19:03:56 +0100 |
| |
On Friday 02 March 2007 18:32, Simon Arlott wrote: > On 02/03/07 16:35, Eric Dumazet wrote:
> > You could just change LOAD_FREQ from (5*HZ) to (5*HZ+1) > > You can see that 5.01 instead of 5.00 second gives the same EXP_xx > > values. > > > > So (5*HZ + 1) is safe. (because HZ >= 100) > > On HZ=1000, this would cause the load average to be pushed towards +1.00 > for up to 2 minutes every ~83 minutes with no obvious cause. (If a task > takes ~10-20ms to run, so 20 runs are needed at HZ=1000 before it passes > it again).
Nope, you dont quite understand how load (avenrun[]) is computed.
Every 5 seconds, three values are adjusted, based on their previous value and the actual value. Lets focus on the first value (mean load average on one minute)
exp = 1.0 / exp(5.0/60.0); avenrun[0] = (avenrun[0] * exp) + (active * (1.0 - exp));
If previous value is 0.0, and current active count 1, then next value for avenrun[0] will be : 0.0799556
Not exactly 1.0 as you think !
Then in the next intervals (if active count is 0), it will decrease 'slowly' : 0.0735627 0.0676809 0.0622695 0.0572907
In average, your load factor close to reality.
Just try my suggestion, it should work. I even proved it in my previous mail :)
Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |