Peter Williams wrote:
I've done some informal testing with smaller values of CAP_STATS_OFFSET
and there is only a minor improvement.
However, something that does improve behaviour for short lived tasks is
to increase the value of HZ. This is because the basic unit of CPU
allocation by the scheduler is 1/HZ and this is also the minimum time
(and granularity) with which sinbinning and other capping measures can
be implemented. This is the fundamental limiting factor for the
accuracy of capping i.e. if everything worked perfectly the best
granularity that can be expected from capping of short lived tasks is
1000 / (HZ * duration) where duration is in seconds.
I already defines CONFIG_HZ=1000. Do you suggest increasing more?
For longer living tasks, once the initial phase has passed the half life
of the Kalman filters takes over from "HZ * duration" in the above
expression. Reducing CAP_STATS_OFFSET will shorten the half life of the
filters and this in turn will make capping coarser. On the other hand,
if the half lives are too big then capping will be too slow in reacting
to changes in a task's CPU usage patterns. So there's a sweet spot in
there somewhere. There's also an upper limit imposed by the likelihood
of arithmetic overflow during the calculations and this has to consider
the fact that the average cycle length (one of the metrics) can be quite
long. The current values was based on these considerations.
Peter
Thanks,
MAEDA Naoaki
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
