[procps] [doublehp@xxxxxxxxxxxx: Bug#674922: procps: top does not behave properly with some SMP machines]
- From: Craig Small <csmall-procps@xxxxxxxxxx>
- To: Procps-ng Mail list <procps@xxxxxxxxxxxxx>
- Date: Tue, 29 May 2012 08:49:57 +1000
Hello Jim,
Was this fixed in procps-ng 3.3.3? The changelog says that hotplug
memory and CPU support was added but I wasn't sure if this sort of case
is covered.
What a curious device!
- Craig
----- Forwarded message from Doublehp <doublehp@xxxxxxxxxxxx> -----
The hardware is a mobile phone: HTC Sensation.
Base software is Android 2.3.5
Above Android, I have installed Debian Stable, using LinuxInstaller by Galoula;
it's doing debootstrap in a chroot.
The CPU has a strange feature: it's dual core, but works a different way than
my laptop;
does not just do freq scaling, but completely shuts the core off on idle time.
On idle time:
root@DHP-ARMEL:~# cat /proc/cpuinfo
Processor : ARMv7 Processor rev 2 (v7l)
processor : 0
BogoMIPS : 13.53
Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3
CPU implementer : 0x51
CPU architecture: 7
CPU variant : 0x0
CPU part : 0x02d
CPU revision : 2
Hardware : pyramid
Revision : 0080
EngineerID : 0007
Serial : 0000000000000000
root@DHP-ARMEL:~#
on busy time:
root@DHP-ARMEL:~# cat /proc/cpuinfo
Processor : ARMv7 Processor rev 2 (v7l)
processor : 0
BogoMIPS : 13.53
processor : 1
BogoMIPS : 13.53
Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3
CPU implementer : 0x51
CPU architecture: 7
CPU variant : 0x0
CPU part : 0x02d
CPU revision : 2
Hardware : pyramid
Revision : 0080
EngineerID : 0007
Serial : 0000000000000000
root@DHP-ARMEL:~#
If top is started in iddle time, the pressing '1' on busy time will show only
one core:
top - 18:34:25 up 1 day, 19:11, 10 users, load average: 11.39, 8.95, 8.09
Tasks: 314 total, 5 running, 307 sleeping, 0 stopped, 2 zombie
Cpu0 : 5.0%us, 94.6%sy, 0.0%ni, 0.0%id, 0.3%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 627676k total, 609084k used, 18592k free, 3448k buffers
Swap: 0k total, 0k used, 0k free, 91492k cached
If top is started on busy time, it will show correctly both cores:
top - 18:35:54 up 1 day, 19:13, 10 users, load average: 11.79, 9.72, 8.44
Tasks: 312 total, 3 running, 307 sleeping, 0 stopped, 2 zombie
Cpu0 : 11.9%us, 88.1%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 4.5%us, 95.5%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 627676k total, 606536k used, 21140k free, 5812k buffers
Swap: 0k total, 0k used, 0k free, 102020k cached
Whether it's showing both cores or not, if it's started on busy time,
when Android will shut down the second core, top will crash:
111 root 20 0 0 0 0 D 1 0.0 3:40.08 emmc-qd
7 root 20 0 0 0 0 S 0 0.0 10:25.33 events/0
top: failed /proc/stat read
root@DHP-ARMEL:~#
Conclusion: top does read the number of cores only at start, and then, assumes
this
number will stay fixed. This is bad. Does not support the number of cores to
change.
I am very surprised, because CPU hotplug is a very old feature, and Linux
does support it since ages; either nobody ever used top on a CPU hotplug
capable machine, or, this CPU is working a different way than traditionnal
CPU hotplug machines.
To test this bug, any mobile device with multi-core should do; not just ARM
but bug should also happen on Intel machines.
-- System Information:
Debian Release: 6.0.2
APT prefers stable
APT policy: (500, 'stable')
Architecture: armel (armv7l)
Kernel: Linux 2.6.35.13-gc35910f (SMP w/1 CPU core; PREEMPT)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968) (ignored: LC_ALL set to C)
Shell: /bin/sh linked to /bin/dash
Versions of packages procps depends on:
ii initscripts 2.88dsf-13.1 scripts for initializing and shutt
ii libc6 2.11.2-10 Embedded GNU C Library: Shared lib
ii libgcc1 1:4.4.5-8 GCC support library
ii libncurses5 5.7+20100313-5 shared libraries for terminal hand
ii libncursesw5 5.7+20100313-5 shared libraries for terminal hand
ii lsb-base 3.2-23.2squeeze1 Linux Standard Base 3.2 init scrip
Versions of packages procps recommends:
ii psmisc 22.11-1 utilities that use the proc file s
procps suggests no packages.
-- no debconf information
----- End forwarded message -----
--
Craig Small VK2XLZ http://enc.com.au/ csmall at : enc.com.au
Debian GNU/Linux http://www.debian.org/ csmall at : debian.org
GPG fingerprint: 5D2F B320 B825 D939 04D2 0519 3938 F96B DF50 FEA5
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