Update obsolete comment about pg_usleep() accuracy.

macdice · macdice · commit e4da2a44c17a · 2023-03-15T17:23:02.000+13:00
There are still some systems that use traditional tick-based sleep timing, but many including Linux, FreeBSD and macOS started using high resolution timer hardware more directly a decade or two ago. Update our comment about that. Also highlight that Windows is like the older Unixen in that respect. Author: Nathan Bossart <nathandbossart@gmail.com> Discussion: https://postgr.es/m/CA%2BhUKG%2BogAon8_V223Ldv6taPR2uKH3X_UJ_A7LJAf3-VRARPA%40mail.gmail.com
diff --git a/src/port/pgsleep.c b/src/port/pgsleep.c
@@ -25,9 +25,10 @@
 /*
  * pg_usleep --- delay the specified number of microseconds.
  *
- * NOTE: although the delay is specified in microseconds, the effective
- * resolution is only 1/HZ, or 10 milliseconds, on most Unixen.  Expect
- * the requested delay to be rounded up to the next resolution boundary.
+ * NOTE: Although the delay is specified in microseconds, older Unixen and
+ * Windows use periodic kernel ticks to wake up, which might increase the delay
+ * time significantly.  We've observed delay increases as large as 20
+ * milliseconds on supported platforms.
  *
  * On machines where "long" is 32 bits, the maximum delay is ~2000 seconds.
  *

Original file line number	Diff line number	Diff line change
`@@ -25,9 +25,10 @@`
`25`	`25`	`/*`
`26`	`26`	`* pg_usleep --- delay the specified number of microseconds.`
`27`	`27`	`*`
`28`		`- * NOTE: although the delay is specified in microseconds, the effective`
`29`		`- * resolution is only 1/HZ, or 10 milliseconds, on most Unixen. Expect`
`30`		`- * the requested delay to be rounded up to the next resolution boundary.`
	`28`	`+ * NOTE: Although the delay is specified in microseconds, older Unixen and`
	`29`	`+ * Windows use periodic kernel ticks to wake up, which might increase the delay`
	`30`	`+ * time significantly. We've observed delay increases as large as 20`
	`31`	`+ * milliseconds on supported platforms.`
`31`	`32`	`*`
`32`	`33`	`* On machines where "long" is 32 bits, the maximum delay is ~2000 seconds.`
`33`	`34`	`*`