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Kernel compilation and different -j# flags
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Hexorg
Tux's lil' helper
Tux's lil' helper


Joined: 29 Oct 2009
Posts: 101

PostPosted: Sat Aug 04, 2012 5:31 pm    Post subject: Kernel compilation and different -j# flags Reply with quote

Hey everyone, I was playing around with my kernel, and decided to find out how the -j flag would change compiling speed.
The machine I used is
Intel Core i7-3773k @ 3.5Mhz (4 cores, 8 threads)
8GB RAM
250 MB/s SSD

I got some interesting data, and decided to share
Code:

Kernel: 3.3.8 (gentoo-sources) x86_64
/usr/src/linux # make
+===============+===================+=======================+
| -j number     | Minutes to finish | % speedup from -j1    |
+===============+===================+=======================+
|   1           | 5.216667          | 100%                  |
|   2           | 2.666667          | 195.6%                |
|   3           | 1.85              | 282.0%                |
|   4           | 1.5               | 347.8%                |
|   5           | 1.383333          | 377.1%                |
|   6           | 1.316667          | 396.2%                |
|   7           | 1.25              | 417.3%                |
|   8           | 1.2               | 434.7%                |
|   9           | 1.2               | 434.7%                |
|   10          | 1.183333          | 440.8%                |
|   11          | 1.2               | 434.7%                |
|   12          | 1.2               | 434.7%                |
|   13          | 1.183333          | 440.8%                |
|   14          | 1.183333          | 440.8%                |
|   15          | 1.2               | 434.7%                |
+===============+===================+=======================+
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Ant P.
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Joined: 18 Apr 2009
Posts: 2303
Location: UK

PostPosted: Sat Aug 04, 2012 5:41 pm    Post subject: Reply with quote

You should test it with a BFS-enabled kernel also.
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