Testers Needed!!

[John Baldwin]

Ok, two patches that I need someone to test.  First off, I have some fixes to 
allow ptrace() to be marked MP safe again w/o generating a lock order 
reversal.  This patch is at 
http://www.FreeBSD.org/~jhb/patches/alpha.ptrace.patch

Note that you will have to do a 'make init_sysent.c' in sys/kern after 
patching to get the updated ptrace flag before building a new kernel.

Second patch is to enable ithread preemption on Alpha which should reduce 
interrupt latency and provide a noticeable performance improvement (it did on 
i386 when we turned it on).  The last time I was playing with having this on, 
I would get lockups under load on my SMP test system (a DS20).  I think the 
reason it locked up was due to migration resulting in the thread that was 
interrupted by an interrupt returning back to PAL on a different CPU and that 
this violated some assumption made by PAL.  To work around this, I use the 
new sched_pin() API to pin the interrupted thread around ithread preemption 
in this patch.  So, this patch needs to be tested on both UP and SMP under 
load (-j 256 world build loops, etc.).  I'm also curious if it does help 
performance at all, or at least the interactive "feel".  Patch is at 
http://www.FreeBSD.org/~jhb/patches/alpha_preempt.patch

Thanks.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org