1 files changed, 19 insertions, 0 deletions
diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index 50de1bed..3873649b 100644
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -466,4 +466,23 @@ sub DESTROY {
  # Sereal doesn't have dclone
  sub deep_clone { ipc_thaw(ipc_freeze($_[-1])) }
  
+sub detect_nproc () {
+        # _SC_NPROCESSORS_ONLN = 84 on both Linux glibc and musl
+        return POSIX::sysconf(84) if $^O eq 'linux';
+        return POSIX::sysconf(58) if $^O eq 'freebsd';
+        # TODO: more OSes
+
+        # getconf(1) is POSIX, but *NPROCESSORS* vars are not
+        for (qw(_NPROCESSORS_ONLN NPROCESSORS_ONLN)) {
+                `getconf $_ 2>/dev/null` =~ /^(\d+)$/ and return $1;
+        }
+        for my $nproc (qw(nproc gnproc)) { # GNU coreutils nproc
+                `$nproc 2>/dev/null` =~ /^(\d+)$/ and return $1;
+        }
+
+        # should we bother with `sysctl hw.ncpu`?  Those only give
+        # us total processor count, not online processor count.
+        undef
+}
+
  1;