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

[David Laight <david%l8s.co.uk@localhost>]

On Wed, Mar 23, 2011 at 05:24:12PM -0400, Thor Lancelot Simon wrote:
> 
> All cores spend well over 50% time in 'sys', even when all or almost
> all are running cc1 processes.

There is some code (in i386, maybe not in amd64) that will generate
a histogram of system calls count/times by call number.
(It probably isn't enabled in generic as it adds code to the entry/exit paths).

When I was writing this I did notice that the build is rather dominated
by open() - probably actually failing opens! (looking for headers)
Quite possibly this single threads.

The build could (probably) be speeded up by generating a single directory
containing symlinks to flatten out the standard -I directory list.

        David

-- 
David Laight: david%l8s.co.uk@localhost