[Interest] Slow compiling on Mac
thiago.macieira at intel.com
Thu Aug 30 14:04:19 CEST 2012
On quinta-feira, 30 de agosto de 2012 15.52.49, Konstantin Tokarev wrote:
> 1. Compilation is not entirely CPU-bound process.
> 2. OS scheduler is not perfect.
The best performance ratio I can get on my dual core x dual thread machine is
375% CPU utilisation, so a -j4 would be recommended.
However, I always build with -j5. My benchmarks show that from -j4 to -j6,
there's minimal difference. if I add more, it starts to slow down again; if I
use fewer, it idles.
The rationale for using more than your number of CPUs is that there's a lot of
I/O involved. Reading from disk is unbearably slow compared to other
I have an SSD, which means it's not that slow, so I don't gain much going from
-j4 to -j5. But on a mechanical hard drive, that is more pronounced.
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel Open Source Technology Center
Intel Sweden AB - Registration Number: 556189-6027
Knarrarnäsgatan 15, 164 40 Kista, Stockholm, Sweden
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