Re: Fw: Regression with hyper threading scheduling

[Peter Williams <pwil3058@bigpond.net.au>]

Andrew Morton wrote:
> 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@gmx.de>
> To: linux-kernel@vger.kernel.org
> Cc: andreas.friedrich@fujitsu-siemens.com
> 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
>
> Some HW-Infos:
> ==============
> lshw
>     description: Mini Tower Computer
>     product: SCENIC P / SCENICO P
>     vendor: FUJITSU SIEMENS
>     version: SCEP
>     serial: YBEM738326
>     width: 32 bits
>     capabilities: smbios-2.31 dmi-2.31
>     configuration: boot=normal chassis=mini-tower uuid=FA48F283-A977-D811-A847-912FD384AB1D
>   *-core
>        description: Motherboard
>        product: D1561
>        vendor: FUJITSU SIEMENS
>        physical id: 0
>        version: S26361-D1561
>        slot: Serial-1
>      *-firmware
>           description: BIOS
>           vendor: FUJITSU SIEMENS // Phoenix Technologies Ltd.
>           physical id: 0
>           version: 5.00 R2.14.1561.01 (11/25/2004)
>           size: 109KB
>           capacity: 448KB
>           capabilities: pci pnp apm upgrade shadowing escd cdboot bootselect int13floppynec int13floppytoshiba int13floppy360 int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer int10video acpi usb agp ls120boot zipboot biosbootspecification
>      *-cpu
>           description: CPU
>           product: Intel(R) Pentium(R) 4 CPU 2.60GHz
>           vendor: Intel Corp.
>           physical id: 4
>           bus info: cpu@0
>           version: 15.2.9
>           slot: CPU
>           size: 2600MHz
>           capacity: 2600MHz
>           width: 32 bits
>           clock: 800MHz
>           capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
>           configuration: id=1
>         *-cache:0
>              description: L1 cache
>              physical id: 5
>              slot: L1 Cache
>              size: 8KB
>              capacity: 32KB
>              capabilities: burst synchronous internal write-through data
>         *-cache:1
>              description: L2 cache
>              physical id: 6
>              slot: L2 Cache
>              size: 512KB
>              capacity: 1MB
>              capabilities: burst internal write-back unified
>         *-cache:2 DISABLED
>              description: L3 cache
>              physical id: 7
>              slot: L3 Cache
>              capacity: 16MB
>              capabilities: internal write-back unified
>         *-logicalcpu:0
>              description: Logical CPU
>              physical id: 1.1
>              width: 32 bits
>              capabilities: logical
>         *-logicalcpu:1
>              description: Logical CPU
>              physical id: 1.2
>              width: 32 bits
>   ...

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.

Peter
--
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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