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Which factor depends on PID_MAX on Linux?

I tested two Linux systems, both of which were 64 bits, but PID_MAX is different for both of them.

In one system (SYSTEM1)

cat /proc/sys/kernel/pid_max
32768

SYSTEM1 configuration:

dmesg | grep -i smp. * allow

getconf PAGESIZE
4096

cat /proc/cpuinfo | awk '/^processor/{print $3}' | tail -1
11
cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 0
siblings    : 6
core id     : 0
cpu cores   : 6
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4389.48
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 1
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 0
siblings    : 6
core id     : 1
cpu cores   : 6
apicid      : 2
initial apicid  : 2
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4389.48
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 2
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 0
siblings    : 6
core id     : 2
cpu cores   : 6
apicid      : 4
initial apicid  : 4
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4389.48
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 3
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 1300.000
cache size  : 15360 KB
physical id : 0
siblings    : 6
core id     : 3
cpu cores   : 6
apicid      : 6
initial apicid  : 6
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4389.48
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 4
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 0
siblings    : 6
core id     : 4
cpu cores   : 6
apicid      : 8
initial apicid  : 8
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4389.48
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 5
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 1200.000
cache size  : 15360 KB
physical id : 0
siblings    : 6
core id     : 5
cpu cores   : 6
apicid      : 10
initial apicid  : 10
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4389.48
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 6
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 1
siblings    : 6
core id     : 0
cpu cores   : 6
apicid      : 32
initial apicid  : 32
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4392.34
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 7
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 1
siblings    : 6
core id     : 1
cpu cores   : 6
apicid      : 34
initial apicid  : 34
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4392.34
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 8
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 1
siblings    : 6
core id     : 2
cpu cores   : 6
apicid      : 36
initial apicid  : 36
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4392.34
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 9
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 2201.000
cache size  : 15360 KB
physical id : 1
siblings    : 6
core id     : 3
cpu cores   : 6
apicid      : 38
initial apicid  : 38
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4392.34
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 10
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 1200.000
cache size  : 15360 KB
physical id : 1
siblings    : 6
core id     : 4
cpu cores   : 6
apicid      : 40
initial apicid  : 40
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4392.34
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

processor   : 11
vendor_id   : GenuineIntel
cpu family  : 6
model       : 45
model name  : Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz
stepping    : 7
microcode   : 1803
cpu MHz     : 1200.000
cache size  : 15360 KB
physical id : 1
siblings    : 6
core id     : 5
cpu cores   : 6
apicid      : 42
initial apicid  : 42
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 pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid
bogomips    : 4392.34
clflush size    : 64
cache_alignment : 64
address sizes   : 46 bits physical, 48 bits virtual
power management:

While for others (SYSTEM2) it was

 cat /proc/sys/kernel/pid_max
65536

SYSTEM2 Configuration:

dmesg | grep -i smp. * allow

SMP: resolution of 64 processors, 61 hotplug processors

getconf PAGESIZE
4096

cat /proc/cpuinfo | awk '/^processor/{print $3}' | tail -1
2

cat /proc/cpuinfo
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 23
model name  : Intel(R) Xeon(R) CPU           X5450  @ 3.00GHz
stepping    : 6
microcode   : 4294967295
cpu MHz     : 2992.467
cache size  : 6144 KB
physical id : 0
siblings    : 3
core id     : 0
cpu cores   : 3
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 10
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc rep_good unfair_spinlock pni ssse3 cx16 sse4_1 hypervisor lahf_lm
bogomips    : 5984.93
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

processor   : 1
vendor_id   : GenuineIntel
cpu family  : 6
model       : 23
model name  : Intel(R) Xeon(R) CPU           X5450  @ 3.00GHz
stepping    : 6
microcode   : 4294967295
cpu MHz     : 2992.467
cache size  : 6144 KB
physical id : 0
siblings    : 3
core id     : 1
cpu cores   : 3
apicid      : 1
initial apicid  : 1
fpu     : yes
fpu_exception   : yes
cpuid level : 10
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc rep_good unfair_spinlock pni ssse3 cx16 sse4_1 hypervisor lahf_lm
bogomips    : 5984.93
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

processor   : 2
vendor_id   : GenuineIntel
cpu family  : 6
model       : 23
model name  : Intel(R) Xeon(R) CPU           X5450  @ 3.00GHz
stepping    : 6
microcode   : 4294967295
cpu MHz     : 2992.467
cache size  : 6144 KB
physical id : 0
siblings    : 3
core id     : 2
cpu cores   : 3
apicid      : 2
initial apicid  : 2
fpu     : yes
fpu_exception   : yes
cpuid level : 10
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx lm constant_tsc rep_good unfair_spinlock pni ssse3 cx16 sse4_1 hypervisor lahf_lm
bogomips    : 5984.93
clflush size    : 64
cache_alignment : 64
address sizes   : 38 bits physical, 48 bits virtual
power management:

From man pages.

proc / sys / kernel / pid_max This file (new in Linux 2.5) indicates the value at which PIDs are wrapped (i.e. the value in this file is equal to the maximum PID). The default value for this file, 32768, results in the same PID range as on earlier kernels. On 32-bit platfroms, 32768 is the maximum value for pid_max. On 64-bit systems, pid_max can be set to any value up to 2 ^ 22 (PID_MAX_LIMIT, about 4 million).

, ​​linux, SYSTEM2 -V.

, , , pid_max? .

+4
1

pid_max , pid.c 597

pid_max = min(pid_max_max, max_t(int, pid_max,
           PIDS_PER_CPU_DEFAULT * num_possible_cpus()));

num_possible_cpus() , ( hotplug, ).

, .

pid_max, PID_MAX_DEFAULT, 0x1000, 0x8000 CONFIG_BASE_SMALL.

pid_max_max, , , , CONFIG_BASE_SMALL PAGE_SIZE. PID_MAX_LIMIT . threads.h 33:

#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
    (sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))

, : (Centos 6):

  • PAGESIZE - 4096
  • CONFIG_BASE_SMALL - 0
  • PID_MAX_DEFAULT 0x8000 (32768)
  • PID_MAX_LIMIT 4 * 1024 * 1024 = 4194304
  • max_pid 4194304 <= max_pid <= 32768

userland CPU /sys/devices/system/cpu/possible. - 0-max, 0-15 16 (, ).

. cputopology.txt.

CPU hotplugging . cpu-hotplug.txt

, .

NB. 4.7.

+5

Source: https://habr.com/ru/post/1655143/

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