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SubjectRe: Inconsistent load average on tickless kernels
On 04/17/2012 05:30 PM, Jonathan Nieder wrote:

>> Looking at results for 2.6.32.55 branch it seems that we're back at
>> 74f5187ac8 patch - the values are almost the same. The difference
>> between NO_HZ and HZ versions is noticeable.
>
> How does 3.0.y + c308b56b53 do? (I ask because the usual flow of
> fixes is mainline -> 3.3.y -> 3.2.y -> 3.0.y -> 2.6.32.y with the
> first three steps happening pretty quickly, so it we can get this
> working on 3.0.y then that would be progress. Also because, like
> 2.6.32.y, 3.0.y is longterm maintained, so it might be useful in the
> meantime.)

It seems that load reported by 3.0.28 with and without c308b56b53 patch
is almost identical to 3.2.12. This might be more clearly visible on a
comparison chart. [1]

2.6.32.55-hz-0f004f5a69 9.88
2.6.32.55-no-hz-74f5187ac8 2.48
2.6.32.55-no-hz-c308b56b53 2.22
3.0.28-hz 10.66
3.0.28-no-hz 0.60
3.0.28-no-hz-c308b56b53 4.09
3.0.28-no-hz-c308b56b53 nohz=off 6.78
3.2.12-hz 10.16
3.2.12-no-hz 0.66
3.2.12-no-hz-c308b56b53 4.36

What's worth noting is that I haven't seen any nasty side effects of the
latest patch on all kernel versions that I've tested. Hope that helps.


[1] http://img855.imageshack.us/img855/2204/kernelload.png

--
Lesław Kopeć

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