Minor suggestion

[Mike Stump]

On Tuesday, December 9, 2003, at 06:31 AM, Alex Hornby wrote:
>> today I was thinking about the gcc compiler. I run a source 
>> distribution (Gentoo Linux), and found out that simultaneous 
>> compilation of multiple packages actually takes longer than compiling 
>> them in sequence, because of scheduling overhead.

Buy a 2-100 processor box, run with make -j2...  You'll notice it is 
faster.

>> Then I asked myself: why does gcc not compile multiple source files 
>> in one go, using threads?

Because it would be even slower.  Benchmark fgetc and then fgetc_unlock 
as used by gzip for an example.

>>  This reduces overhead and is still quicker, mainly because for 
>> example header files only have to be compiled once,

You've just described the compile server.  Congratulations.  I just did 
a hello world benchmark, 91x faster.  Note however, that it doesn't use 
threads.  It just uses an in memory db of past compilations for 
eliminating future work.  All compile serialize through each server, 
and every server is logically independent, except they all share the 
same load balancer to distribute load evenly among n processors.  By 
not having threads, there is no locking required.  In time, we may 
share the db in a course way between processors.

>> I realise that this would mean a huge rewrite

Not that bad actually.