I have a bug in my Linux app that is reproducable only on single-core CPUs. To debug it, I want to start the process from the command line so that it is limited to 1 CPU even on my multi-processor machine.

Is it possible to change this for a particular process, e.g. to run it so that it does not run (its) multiple threads on multiple processors?

  • It's up to the program running in the process how many threads it creates. – Johan Myréen Sep 8 '18 at 8:39
  • How does your application determine how many threads to spawn? Depending on how your app checks the number of cores (e.g. via std::thread::hardware_concurrency, sysconf(_SC_NPROCESSORS_ONLN), /proc/cpuinfo, cpuid, etc) there may be different approaches to fake the core count. That said, as suggested by @JohanMyréen, at that point it may be easier to hardcode how many threads to spawn. – undercat Sep 8 '18 at 9:33
  • By the way, it may be worth mentioning what language and threading library you are using. – undercat Sep 8 '18 at 9:37
  • Would not be easier changing you own sources? (....) – Rui F Ribeiro Sep 8 '18 at 17:13

You can use taskset from util-linux.

The masks may be specified in hexadecimal (with or without a leading "0x"), or as a CPU list with the --cpu-list option. For example,

       0x00000001  is processor #0,

       0x00000003  is processors #0 and #1,

       0xFFFFFFFF  is processors #0 through #31,

       32          is processors #1, #4, and #5,

       --cpu-list 0-2,6
                   is processors #0, #1, #2, and #6.

   When  taskset returns, it is guaranteed that the given program has been
   scheduled to a legal CPU.

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