[sparc64] limit cpu shown on active (online) cpus only?

[mator]

Hello!

After PR #656 htop shows all available CPUs , instead of active ones. How do i limit it to show it to only active CPUs?

For example, on sparc64 linux platform, under LDOM (read virtual machine), there's only particular list of CPUs available for LDOM. I.e. my LDOM has 8 active CPUs (allocated for VM from hypervisor):

$ nproc  --all
256
$ nproc
8
$ lscpu
Architecture:        sparc64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Big Endian
CPU(s):              8
On-line CPU(s) list: 0-7
Thread(s) per core:  8
Core(s) per socket:  1
Socket(s):           1
Model name:          UltraSparc T5 (Niagara5)
Flags:               sun4v

and there's no point to show unavailable (256-8 == 248) CPUs (which would 0 load anyway).

This is how htop (3.0.5) was looking before:

    0[                                       0.0%]     4[                                       0.0%]
    1[|||                                    3.8%]     5[|                                      0.6%]
    2[                                       0.0%]     6[||                                     1.3%]
    3[                                       0.0%]     7[|                                      0.6%]
  Mem[||||||||                         641M/15.7G]   Tasks: 29, 6 thr; 1 running
  Swp[                                    0K/769M]   Load average: 0.02 0.01 0.00
                                                     Uptime: 1 day, 09:05:00
                                                     Date & Time: 2021-08-21 22:43:56

    PID USER      PRI  NI  VIRT   RES   SHR S CPU%▽MEM%   TIME+  Command
  77472 mator      25   5 29816  4896  3640 R  3.2  0.0  0:00.25 htop
      1 root       20   0  185M 10336  7256 S  0.0  0.1  0:12.01 /sbin/init
    282 root       20   0  164M 75944 74616 S  0.0  0.5  0:07.75 /lib/systemd/systemd-journald

and this is how it (3.1.0-dev) looks now:

    0[                                                                                0.0%]   128[                                                                                0.0%]
    1[||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||100.0%]   129[                                                                                0.0%]
    2[                                                                                0.0%]   130[                                                                                0.0%]
    3[                                                                                0.0%]   131[                                                                                0.0%]
    4[                                                                                0.0%]   132[                                                                                0.0%]
    5[                                                                                0.0%]   133[                                                                                0.0%]
    6[                                                                                0.0%]   134[                                                                                0.0%]
    7[                                                                                0.0%]   135[                                                                                0.0%]
    8[                                                                                0.0%]   136[                                                                                0.0%]
    9[                                                                                0.0%]   137[                                                                                0.0%]
   10[                                                                                0.0%]   138[                                                                                0.0%]
   11[                                                                                0.0%]   139[                                                                                0.0%]
   12[                                                                                0.0%]   140[                                                                                0.0%]
   13[                                                                                0.0%]   141[                                                                                0.0%]
   14[                                                                                0.0%]   142[                                                                                0.0%]
   15[                                                                                0.0%]   143[                                                                                0.0%]
   16[                                                                                0.0%]   144[                                                                                0.0%]
   17[                                                                                0.0%]   145[                                                                                0.0%]
   18[                                                                                0.0%]   146[                                                                                0.0%]
   19[                                                                                0.0%]   147[                                                                                0.0%]
   20[                                                                                0.0%]   148[                                                                                0.0%]
   21[                                                                                0.0%]   149[                                                                                0.0%]
   22[                                                                                0.0%]   150[                                                                                0.0%]
   23[                                                                                0.0%]   151[                                                                                0.0%]
   24[                                                                                0.0%]   152[                                                                                0.0%]
   25[                                                                                0.0%]   153[                                                                                0.0%]
   26[                                                                                0.0%]   154[                                                                                0.0%]
   27[                                                                                0.0%]   155[                                                                                0.0%]
   28[                                                                                0.0%]   156[                                                                                0.0%]
   29[                                                                                0.0%]   157[                                                                                0.0%]
   30[                                                                                0.0%]   158[                                                                                0.0%]
   31[                                                                                0.0%]   159[                                                                                0.0%]
   32[                                                                                0.0%]   160[                                                                                0.0%]
   33[                                                                                0.0%]   161[                                                                                0.0%]
   34[                                                                                0.0%]   162[                                                                                0.0%]
   35[                                                                                0.0%]   163[                                                                                0.0%]
   36[                                                                                0.0%]   164[                                                                                0.0%]
   37[                                                                                0.0%]   165[                                                                                0.0%]
   38[                                                                                0.0%]   166[                                                                                0.0%]
   39[                                                                                0.0%]   167[                                                                                0.0%]
   40[                                                                                0.0%]   168[                                                                                0.0%]
   41[                                                                                0.0%]   169[                                                                                0.0%]
   42[                                                                                0.0%]   170[                                                                                0.0%]
   43[                                                                                0.0%]   171[                                                                                0.0%]
   44[                                                                                0.0%]   172[                                                                                0.0%]
   45[                                                                                0.0%]   173[                                                                                0.0%]
   46[                                                                                0.0%]   174[                                                                                0.0%]
   47[                                                                                0.0%]   175[                                                                                0.0%]
   48[                                                                                0.0%]   176[                                                                                0.0%]
   49[                                                                                0.0%]   177[                                                                                0.0%]
   50[                                                                                0.0%]   178[                                                                                0.0%]
   51[                                                                                0.0%]   179[                                                                                0.0%]
   52[                                                                                0.0%]   180[                                                                                0.0%]
   53[                                                                                0.0%]   181[                                                                                0.0%]
   54[                                                                                0.0%]   182[                                                                                0.0%]
   55[                                                                                0.0%]   183[                                                                                0.0%]
   56[                                                                                0.0%]   184[                                                                                0.0%]
   57[                                                                                0.0%]   185[                                                                                0.0%]
   58[                                                                                0.0%]   186[                                                                                0.0%]
   59[                                                                                0.0%]   187[                                                                                0.0%]
   60[                                                                                0.0%]   188[                                                                                0.0%]
   61[                                                                                0.0%]   189[                                                                                0.0%]
   62[                                                                                0.0%]   190[                                                                                0.0%]
   63[                                                                                0.0%]   191[                                                                                0.0%]
   64[                                                                                0.0%]   192[                                                                                0.0%]
   65[                                                                                0.0%]   193[                                                                                0.0%]
   66[                                                                                0.0%]   194[                                                                                0.0%]
   67[                                                                                0.0%]   195[                                                                                0.0%]
   68[                                                                                0.0%]   196[                                                                                0.0%]
   69[                                                                                0.0%]   197[                                                                                0.0%]
   70[                                                                                0.0%]   198[                                                                                0.0%]
   71[                                                                                0.0%]   199[                                                                                0.0%]
   72[                                                                                0.0%]   200[                                                                                0.0%]
   73[                                                                                0.0%]   201[                                                                                0.0%]
   74[                                                                                0.0%]   202[                                                                                0.0%]
   75[                                                                                0.0%]   203[                                                                                0.0%]
   76[                                                                                0.0%]   204[                                                                                0.0%]
   77[                                                                                0.0%]   205[                                                                                0.0%]
   78[                                                                                0.0%]   206[                                                                                0.0%]
   79[                                                                                0.0%]   207[                                                                                0.0%]
   80[                                                                                0.0%]   208[                                                                                0.0%]
   81[                                                                                0.0%]   209[                                                                                0.0%]
   82[                                                                                0.0%]   210[                                                                                0.0%]
   83[                                                                                0.0%]   211[                                                                                0.0%]
   84[                                                                                0.0%]   212[                                                                                0.0%]
   85[                                                                                0.0%]   213[                                                                                0.0%]
   86[                                                                                0.0%]   214[                                                                                0.0%]
   87[                                                                                0.0%]   215[                                                                                0.0%]
   88[                                                                                0.0%]   216[                                                                                0.0%]
   89[                                                                                0.0%]   217[                                                                                0.0%]
   90[                                                                                0.0%]   218[                                                                                0.0%]
   91[                                                                                0.0%]   219[                                                                                0.0%]
   92[                                                                                0.0%]   220[                                                                                0.0%]
   93[                                                                                0.0%]   221[                                                                                0.0%]
   94[                                                                                0.0%]   222[                                                                                0.0%]
   95[                                                                                0.0%]   223[                                                                                0.0%]
   96[                                                                                0.0%]   224[                                                                                0.0%]
   97[                                                                                0.0%]   225[                                                                                0.0%]
   98[                                                                                0.0%]   226[                                                                                0.0%]
   99[                                                                                0.0%]   227[                                                                                0.0%]
  100[                                                                                0.0%]   228[                                                                                0.0%]
  101[                                                                                0.0%]   229[                                                                                0.0%]
  102[                                                                                0.0%]   230[                                                                                0.0%]
  103[                                                                                0.0%]   231[                                                                                0.0%]
  104[                                                                                0.0%]   232[                                                                                0.0%]
  105[                                                                                0.0%]   233[                                                                                0.0%]
  106[                                                                                0.0%]   234[                                                                                0.0%]
  107[                                                                                0.0%]   235[                                                                                0.0%]
  108[                                                                                0.0%]   236[                                                                                0.0%]
  109[                                                                                0.0%]   237[                                                                                0.0%]
  110[                                                                                0.0%]   238[                                                                                0.0%]
  111[                                                                                0.0%]   239[                                                                                0.0%]
  112[                                                                                0.0%]   240[                                                                                0.0%]
  113[                                                                                0.0%]   241[                                                                                0.0%]
  114[                                                                                0.0%]   242[                                                                                0.0%]
  115[                                                                                0.0%]   243[                                                                                0.0%]
  116[                                                                                0.0%]   244[                                                                                0.0%]
  117[                                                                                0.0%]   245[                                                                                0.0%]
  118[                                                                                0.0%]   246[                                                                                0.0%]
  119[                                                                                0.0%]   247[                                                                                0.0%]
  120[                                                                                0.0%]   248[                                                                                0.0%]
  121[                                                                                0.0%]   249[                                                                                0.0%]
  122[                                                                                0.0%]   250[                                                                                0.0%]
  123[                                                                                0.0%]   251[                                                                                0.0%]
  124[                                                                                0.0%]   252[                                                                                0.0%]
  125[                                                                                0.0%]   253[                                                                                0.0%]
  126[                                                                                0.0%]   254[                                                                                0.0%]
  127[                                                                                0.0%]   255[                                                                                0.0%]
  Mem[|||||||||||||||                                                           995M/15.7G]   Tasks: 29, 6 thr, 107 kthr; 2 running
  Swp[                                                                             0K/769M]   Load average: 0.09 0.02 0.01
                                                                                              Uptime: 1 day, 09:08:50

    PID USER      PRI  NI  VIRT   RES   SHR S CPU%▽MEM%   TIME+  Command
  77491 mator      25   5 29448  6728  3600 R 3357  0.0  0:00.40 ./htop
      1 root       20   0  185M 10336  7256 S  0.0  0.1  0:12.01 /sbin/init
    282 root       20   0  164M 75968 74640 S  0.0  0.5  0:07.75 /lib/systemd/systemd-journald
    317 root       20   0 42664  5840  4312 S  0.0  0.0  0:01.07 /lib/systemd/systemd-udevd

[cgzones]

Can you please post the output of /proc/stat and the contents of /sys/devices/system/cpu/cpu127/ and /sys/devices/system/cpu/cpu127/online (or of any other non active CPU).
Htop seems not to recognize the non-online CPUs as inactive.

[mator]

$ cat /proc/stat
cpu  8477 139861 113330 167608263 31848 0 1718 0 0 0
cpu0 1068 17044 24846 20950687 3501 0 20 0 0 0
cpu1 1213 19162 13566 20948701 7502 0 66 0 0 0
cpu2 858 19855 14322 20957078 1418 0 48 0 0 0
cpu3 1665 15851 12110 20920013 5878 0 1518 0 0 0
cpu4 724 17790 12005 20959885 1670 0 24 0 0 0
cpu5 1245 16615 12460 20951945 5334 0 15 0 0 0
cpu6 878 16927 13908 20956061 5453 0 14 0 0 0
cpu7 824 16613 10111 20963888 1090 0 10 0 0 0
intr 9021833 7516062 0 0 16 0 23485 0 399 0 29955 0 1115899 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 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 8715516
btime 1629455936
processes 82050
procs_running 1
procs_blocked 0
softirq 11961941 0 2149071 164053 1115908 224 0 2 3406064 258 5126361

$ ls /sys/devices/system/cpu/cpu127/
hotplug  subsystem  uevent
$ ls /sys/devices/system/cpu/cpu0/
clock_tick  hotplug  l1_dcache_line_size  l1_dcache_size  l1_icache_line_size  l1_icache_size  l2_cache_line_size  l2_cache_size  subsystem  topology  uevent
$ cat /sys/devices/system/cpu/online
0-7
$ cat /sys/devices/system/cpu/possible
0-255
$ cat /sys/devices/system/cpu/present
0-7
$ cat /sys/devices/system/cpu/offline
8-255

PS: there's util-linux dump from a physical machine (not a VM) with all cpus online, which is not exactly my case, but could be probably useful.

[zv-io]

An additional data point: the CPU% field is off by a factor of the ratio of online-vs-offline CPUs:

In this example, 32 threads of a possible 128 are allocated to the Linux LDOM, and the CPU% column is incorrectly scaled by a factor of 4.

[glaubitz]

There is a very obvious bug here which is determining the amount of active CPUs on Linux using a custom implementation equivalent to sysconf(_SC_NPROCESSORS_CONF) which returns the number of all CPUs in a system while sysconf(_SC_NPROCESSORS_ONLN) will actually return the number of online CPUs which is what we want here.

The corresponding Solaris code actually does it correctly [1]:

   s = sysconf(_SC_NPROCESSORS_ONLN);
   if (s < 1)
      CRT_fatalError("Cannot get active CPU count by sysconf(_SC_NPROCESSORS_ONLN)");

   if (s != super->activeCPUs) {
      change = true;
      hsuper->activeCPUs = s;
   }

while the corresponding Linux code reads out /sys/devices/system/cpu [2] and tries to determine the number of active CPUs with its own algorithm which fails.

The obvious solution would be to determine the number of active CPUs using sysconf(_SC_NPROCESSORS_ONLN), i.e. simply imitating what the Solaris code already does.

[1] https://github.com/htop-dev/htop/blob/main/solaris/SolarisMachine.c#L53

[2] https://github.com/htop-dev/htop/blob/main/linux/LinuxMachine.c#L43