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Re: high sys time, very very slow builds on new 24-core system

On 03/23/11 22:24, Thor Lancelot Simon wrote:
I have a new machine with 24 2Ghz Opteron cores.  It has 32GB of RAM.

Building with sources on a fast SSD ("preloaded" into the page
cache before the build using tar>  /dev/null) and obj, dest, and rel
dirs on tmpfs, system builds are extraordinarily slow.  The system
takes about 20 minutes to build a netbsd-5 based source tree
with -j24 -- about the same amount of time as an older 8-core Intel
based system running netbsd-5 requires with -j8.

All cores spend well over 50% time in 'sys', even when all or almost
all are running cc1 processes.  The kernel is amd64 -current GENERIC
from about 1 week ago -- no DIAGNOSTIC, DEBUG, KMEMSTATS, LOCKDEBUG,

Does anyone have any idea what might be wrong here?

Implement CPU-topology detection for your CPU.
This lets our scheduler work more efficiently.


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