2.4 limits locks to half of physical mem; MCL_FUTURE bug note

man2/mlockall.2

@@ -26,8 +26,11 @@
 .\"      First version written
 .\" Modified, 27 May 2004, Michael Kerrisk <mtk-manpages@gmx.net>
 .\"     Added notes on capability requirements
+.\" Modified, 2004-11-23, mtk, Noted buggy MCL_FUTURE behaviour in 2.4.x
+.\" Modified, 2004-11-25, mtk, 2.4 limits locks to half of physical mem.
+.\" Modified, 2004-11-25, mtk, Noted MCL_FUTURE bug in 2.4.x, x < 18
 .\"
-.TH MLOCKALL 2 2004-05-27 "Linux 2.6.6" "Linux Programmer's Manual"
+.TH MLOCKALL 2 2004-11-25 "Linux 2.6.9" "Linux Programmer's Manual"
 .SH NAME
 mlockall \- disable paging for calling process
 .SH SYNOPSIS
@@ -113,6 +116,9 @@ will be unlocked by a single call to
 Pages which are mapped to several locations or by several processes stay
 locked into RAM as long as they are locked at least at one location or by
 at least one process.
+.SH "NOTES"
+In Linux 2.4 and earlier, the kernel prevents a single process
+from locking more than half of RAM.
 .SH "RETURN VALUE"
 On success,
 .B mlockall
@@ -134,6 +140,13 @@ The calling process has insufficient privilege to call
 Under Linux the
 .B CAP_IPC_LOCK
 capability is required.
+.SH "BUGS"
+In the 2.4 series Linux kernels up to and including 2.4.17,
+a bug caused the
+.B MCL_FUTURE
+flag to be inherited across a
+.BR fork (2).
+This was rectified in kernel 2.4.18.
 .SH AVAILABILITY
 On POSIX systems on which
 .B mlockall
@@ -152,5 +165,6 @@ POSIX.1b, SVr4.   SVr4 documents an additional EAGAIN error code.
 .BR mlock (2),
 .BR munlock (2),
 .BR munlockall (2),
+.BR setrlimit (2),
 .BR sysconf (3),
 .BR capabilities (7)