Re: cloning the kernel - why long time in "Resolving 313037 deltas"

On Thursday December 21st 2006 at 20:44 Kyle Moffett wrote:

I've actually also seen filesystem operation latency double or triple  
if you start trying to do operations from multiple threads at once.   
Suddenly the already dog-slow single-CPU operations start bouncing  
caches and the Mac OS X mostly-whole-of-BSD-BKL across CPUs and it  
just crawls.  I can definitely see the local disk IO taking 100x  
longer than the network I/O, especially with an 8-megabit internet link.

The mmap() implementation on Mac OS X ate 85% percent of system time on
the old version for git-index-pack. Of that time nearly all was spent on
some Mach locking function. So yes the BKL like locking inside the Mach
message passing seems to be the big culprit, perhaps Andy Tanenbaum can
explain this on LCA 2007. <ducks>

As most developers now run multicore CPU's we notice these differences
even better now! ;-)
-- 
Marco Roeland