linux-kernel - 3.10.9: kmemleak disables all CPUs except CPU0

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Date:	Sat, 31 Aug 2013 15:35:21 +0200
From:	Martin MOKREJŠ <mmokrejs@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Subject: 3.10.9: kmemleak disables all CPUs except CPU0

Hi,
  never realized that my CPUs are gone if I compile into kernel kmemleak.
Is that really the aim?


CONFIG_HAVE_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK=y
CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=400
# CONFIG_DEBUG_KMEMLEAK_TEST is not set
# CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF is not set



1.  Why isn't there /sys/devices/system/cpu/cpu0/online file?
Does not matter if it contains 0 or 1. It just should exist.

# cat  /sys/devices/system/cpu/cpu0/online
cat: /sys/devices/system/cpu/cpu0/online: No such file or directory
# cat  /sys/devices/system/cpu/cpu1/online
0
# cat  /sys/devices/system/cpu/cpu2/online
0
# cat  /sys/devices/system/cpu/cpu3/online
0
#


2. So which CPU is actually enabled now? Looks cpuinfo really say only one core is up.

# cat /proc/cpuinfo 
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 42
model name      : Intel(R) Core(TM) i7-2640M CPU @ 2.80GHz
stepping        : 7
microcode       : 0x28
cpu MHz         : 3472.000
cache size      : 4096 KB
physical id     : 0
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu 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 syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid
bogomips        : 5587.30
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

#



3. Complete dmesg is attached but here are few lines:

[    0.000000] Linux version 3.10.9-default-pciehp (root@...tro) (gcc version 4.6.3 (Gentoo 4.6.3 p1.8, pie-0.5.2) ) #8 SMP Tue Aug 27 01:37:03 MEST 2013
[    0.000000] Command line: root=/dev/sda5 slub_debug=AFPZ pciehp.pciehp_debug=1 pciehp_debug=1

[    0.000000] smpboot: Allowing 4 CPUs, 0 hotplug CPUs
[    0.000000] nr_irqs_gsi: 40

[    0.000000] setup_percpu: NR_CPUS:4 nr_cpumask_bits:4 nr_cpu_ids:4 nr_node_ids:1
[    0.000000] PERCPU: Embedded 26 pages/cpu @ffff88041d800000 s77760 r8192 d20544 u524288
[    0.000000] pcpu-alloc: s77760 r8192 d20544 u524288 alloc=1*2097152
[    0.000000] pcpu-alloc: [0] 0 1 2 3 

[    0.343650] smpboot: CPU0: Intel(R) Core(TM) i7-2640M CPU @ 2.80GHz (fam: 06, model: 2a, stepping: 07)
[    0.343879] TSC deadline timer enabled
[    0.343893] Performance Events: PEBS fmt1+, 16-deep LBR, SandyBridge events, Intel PMU driver.
[    0.344158] perf_event_intel: PEBS disabled due to CPU errata, please upgrade microcode
[    0.344272] ... version:                3
[    0.344345] ... bit width:              48
[    0.344418] ... generic registers:      4
[    0.344491] ... value mask:             0000ffffffffffff
[    0.344565] ... max period:             000000007fffffff
[    0.344639] ... fixed-purpose events:   3
[    0.344711] ... event mask:             000000070000000f
[    0.344840] kmemcheck: Limiting number of CPUs to 1.
[    0.344915] kmemcheck: Initialized
[    0.345949] Brought up 1 CPUs
[    0.346023] smpboot: Total of 1 processors activated (5587.30 BogoMIPS)



4. If it is really intentional that kmemleak inclusion enforces only one CPU then I would
to get a fat warning in the help text kernel config and also a runtime warning in dmesg.


5. While we are at it, could somebody ensure me that in a dual physical core CPU
with hyperthreading enabled I get in linux:

cpu0 - 1st physical core
cpu1 - 2nd physical core
cpu2 - 1st hyperthreaded core adjacent to cpu0
cpu3 - 2nd hyperthreaded core adjacent to cpu1

If that is NOT case what is then in my case 
CONFIG_NR_CPUS=2
would keep enabled 1st physical core and is hyperthreaded core which is of course not what I want.

So far my .config has:
CONFIG_X86_HT=y
CONFIG_NR_CPUS=4
SCHED_SMT=N
SCHED_MC=N


Thank you,
Martin

View attachment "dmesg-3.10.9.kmemleak.txt" of type "text/plain" (66157 bytes)