From fcf8c622fd3d4e288c40205bd0f745eeb5844705 Mon Sep 17 00:00:00 2001 From: normal Date: Fri, 6 Jul 2018 02:15:05 +0000 Subject: [PATCH] thread.c (ruby_ppoll): improve timespec to msec conversion Round up non-zero <1ms timeouts to 1ms and use INT_MAX instead of infinite (-1) for extremely large timeouts. All of our ppoll/select callers are able to handle spurious wakeups, anyways. This avoids excessive CPU usage and busy waits with short timeouts to rb_wait_for_single_fd. CPU usage with the following script is significantly reduced for systems with "#undef HAVE_PPOLL": require 'io/wait' r, w = IO.pipe Thread.new { loop { r.wait_readable(0.000001) } }.join(5) exit!(0) Low-resolution in poll(2) still sucks, though... Note: I don't see the value in making a similar change to time_timeval of a <1us sleep is attempted because of GVL release and syscall latency. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63867 b2dd03c8-39d4-4d8f-98ff-823fe69b080e --- thread.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/thread.c b/thread.c index ae80a70682..360807b073 100644 --- a/thread.c +++ b/thread.c @@ -3971,12 +3971,13 @@ ruby_ppoll(struct pollfd *fds, nfds_t nfds, int tmp, tmp2; if (ts->tv_sec > INT_MAX/1000) - timeout_ms = -1; + timeout_ms = INT_MAX; else { tmp = (int)(ts->tv_sec * 1000); - tmp2 = (int)(ts->tv_nsec / (1000 * 1000)); + /* round up 1ns to 1ms to avoid excessive wakeups for <1ms sleep */ + tmp2 = (int)((ts->tv_nsec + 999999L) / (1000L * 1000L)); if (INT_MAX - tmp < tmp2) - timeout_ms = -1; + timeout_ms = INT_MAX; else timeout_ms = (int)(tmp + tmp2); }