SPID, threads in ps
Modern ps can show thread
The SPID column is the thread id. As far as I can tell,
LWP and SPID are the same thing; I am not sure what the value of NLWP is;
it appears to be just the count of threads. Use "ps -Lf" to see that column.
-L show threads, possibly with LWP and NLWP columns
-T show threads, possibly with SPID column
-m show threads after processes
H show threads as if they were processes
m show threads after processes
The ps man and info pages
don't tell you much about threads, probably because there's
been plenty of confusion and disagreement about how the
kernel should expose thread info, how /proc should pick it
up, etc. This old thread shows some of that. Also, Uncertainty about
implementation details probably didn't help either.
There are some better man pages out there.
Here's the threads of mysqld on a Linux system:
$ ps -p 677 -T
PID SPID TTY TIME CMD
677 677 ? 00:00:00 mysqld
677 678 ? 00:00:00 mysqld
677 679 ? 00:00:00 mysqld
677 680 ? 00:00:00 mysqld
677 681 ? 00:00:00 mysqld
677 682 ? 00:00:00 mysqld
677 683 ? 00:00:00 mysqld
677 684 ? 00:00:00 mysqld
677 685 ? 00:00:00 mysqld
677 686 ? 00:00:00 mysqld
Different Unixes have widely different implementations of how
thread info is shown and what is displayed. Be sure to check
the man pages carefully.
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