nptl threads, gdb, Nsquared

[David Anderson <davea at quasar dot engr dot sgi dot com>]

I'd be pleased to be wrong here. but it seems that with nptl
pthreads apps under gdb on GNU/Linux that (oversimplifing 
significantly) register saving is N-squared:

Say there are N registers (around 300 for Intel Itanium)

regcache_save(), for each register  call do_cooked_read()
  For each register,i.e, N times, do_cooked_read calls
    thread_db_fetch_registers calls on libthread_db.so requesting
    all registers (libthread_db.so calls back  to ps_lgetregs() in gdb
    which requests _all_ registers and calls to thread_db_fetch_registers).
    For each register  fetch_register () in inf_ptrace.c 
      is called (Loading is now N**2) .

So each register fetch of 300 regs results in fetching 300*300 registers.

This is painfully slow.

Have I got this all wrong?
I presume this is well known though.
Comments? References to gdb threads/bug-reports?

Thanks.
David Anderson davea at sgi dot com.