Messages in this thread | | | Subject | Re: High CPU load when machine is idle (related to PROBLEM: Unusually high load average when idle in 2.6.35, 2.6.35.1 and later) | From | Peter Zijlstra <> | Date | Tue, 26 Oct 2010 16:05:58 +0200 |
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On Tue, 2010-10-26 at 14:44 +0200, Peter Zijlstra wrote: > a smarter patch will try and avoid that loop.
a1 = a0 * e + a * (1 - e)
a2 = a1 * e + a * (1 - e) = (a0 * e + a * (1 - e)) * e + a * (1 - e) = a0 * e^2 + a * (1 - e) * (1 + e)
a3 = a2 * e + a * (1 - e) = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e) = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e) = a0 * e^n + a * (1 - e^n)
the trouble seems to be that that is a rather slow function, stuffing that in a table will either give us very large tables or very coarse decay.
n: an an * 2048
1: 0.99446 2037 2: 0.98895 2025 4: 0.978023 2003 8: 0.956529 1959 16: 0.914947 1874 32: 0.837128 1714 64: 0.700784 1435 128: 0.491098 1006 256: 0.241177 494 512: 0.0581666 119 1024: 0.00338335 7 2048: 1.14471e-05 0
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