Andrew Morton wrote:[bits deleted]fyi.. (if replying, please be sure to do it on-list)
Begin forwarded message:
Date: Thu, 17 Aug 2006 13:40:42 +0200
From: Wolfgang Erig <Wolfgang.Erig@xxxxxx>
To: linux-kernel@xxxxxxxxxxxxxxx
Cc: andreas.friedrich@xxxxxxxxxxxxxxxxxxx
Subject: Regression with hyper threading scheduling
Hello kernel hacker,
I have a regression with Hyper-Threading in my box.
If I try e.g. 'while true; do ((ii+=1)); done' on two xterms
- with 2.6.8 both CPUs are running (looking at gkrellm or /proc/stat)
- with 2.6.15/2.6.17 etc. only one CPU is running, sometimes CPU0, sometimes CPU1
Any idea? If you need more info, let me know,
Wolfgang
Kernel 2.6.8.1: Hyper-Threading works:
======================================
uname -a
Linux oak 2.6.8.1 #1 SMP Wed May 10 13:24:21 CEST 2006 i686 GNU/Linux
cat /proc/stat
cpu 22709 4502 2543 1008491 2881 92 1475
cpu0 12800 2428 1426 501276 1859 92 1472
cpu1 9909 2074 1117 507215 1021 0 2
intr 5909520 5214423 7297 0 2 2 0 2 1 0 0 0 0 92935 0 7422 13 0 224861 42603 0 0 0 319959 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 6553093
btime 1155801409
processes 2525
procs_running 3
procs_blocked 0
Kernel 2.6.17.8 etc.: Hyper-Threading does not work:
====================================================
uname -a
Linux oak 2.6.17.8 #2 SMP PREEMPT Thu Aug 17 11:40:04 CEST 2006 i686 GNU/Linux
cat /proc/stat
cpu 5049 0 744 137292 3113 18 3 0
cpu0 36 0 53 72732 282 18 1 0
cpu1 5012 0 690 64560 2831 0 2 0
intr 221093 182798 880 0 3 4 0 3 1 0 0 0 0 28863 0 6718 12 1811 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 458461
btime 1155807757
processes 3203
procs_running 1
procs_blocked 0
I'm unable to reproduce this problem with 2.6.18-rc4 on my HT system. I'm using top with the "last processor" field enabled to observe (rather than the methods described) and the two bash shells are both getting 100% and are each firmly affixed to different CPUs.