See also the FAQ entry.

IRC, freenode, #hurd, 2012-09-30

<braunr> i expect smp to be our next gsoc project

IRC, freenode, #hurd, 2013-01-02

<braunr> i'd like to mentor someone for adding smp to gnumach

IRC, freenode, #hurd, 2013-03-14

<braunr> but i'm afraid we'll have to fight obscur smp-safety issues
<braunr> for one, drivers are much probably not smp safe and would require
  a big kernel lock
<braunr> userspace (such as signal delivery in libc) might be affected too
<braunr> smp isn't that easy

Richard, 2013-03-20

This task actually looks too big for a GSoC project.

IRC, freenode, #hurd, 2013-09-30

<braunr> also, while the problem with hurd is about I/O, it's actually a
  lot more about caching, and even with more data cached in, the true
  problem is contention, in which case having several processors would
  actually slow things down even more