David Schwartz wrote:
According to my formula:
time(minutes) = 1e5 / ( speed(MHz) * nproc )
and taking nproc = 1, this results in
time = 1e5 / 2798.66 = 36 minutes
Quite accurate for your system as well. At least this formula gives a
resonable estimate about the compile time.
Apparently HT does not help much, since with SMP kernel, times do not
get any close to 36/2 = 18 minutes. However, there is a slight improvement
from -j1 to -j2 with SMP.
You're saying that HT does not help because it doesn't double the speed?
That makes no sense. HT helps if it brings the time down. If it brings it
down to 34 minutes, it helps a little. If it brings it down to 24 minutes,
it helps quite a bit. It's unrealistic to even imagine that HT will bring
anything close to the benefit of a second physical CPU.
OK, sorry for me rushing into conclusions. All I tried to say was that in
cases when 'nproc' plays are role, then nproc=2 with a second CPU, but it
is somewhere between 1 and 2 for HT systems; possibly closer to 1 than to
2 (but indeed still larger than 1 !)
Rob.
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