At compile-time, GNU Mach is parameterized with several constants. These might need some tuning. Debian has some patches.

IRC, freenode, #hurd, 2011-06-09

<braunr> youpi: in ipc/ipc_hash.c, there is code which computes the size of
  the global (space, port)->entry hash table
<braunr> youpi: you may be interested in tuning this one too
<youpi> I know
<braunr> ok
<youpi> the current value is not so bad
<youpi> it's big enough for buildds to run fine
<braunr> 256 if i'm right
<braunr> well
<braunr> it won't fail
<youpi> we're limited by the 4000 object limitation anyway
<braunr> since it's a chained hash table
<braunr> but increasing it may help performances a bit
<braunr> and it certainly can't hurt much