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Date:      Sat, 10 Nov 2018 23:07:46 +0000 (UTC)
From:      Edward Tomasz Napierala <trasz@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r340339 - in head: lib/libc/net share/man/man5
Message-ID:  <201811102307.wAAN7kka037505@repo.freebsd.org>

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Author: trasz
Date: Sat Nov 10 23:07:46 2018
New Revision: 340339
URL: https://svnweb.freebsd.org/changeset/base/340339

Log:
  Don't call stat(2) on nsswitch.conf(5) every time nsdispatch(3)
  and dependent functions (eg getpwname(3)) get called. This can
  improve performance of binaries that perform a lot of name
  lookups, such as gssd(8). It also matches documented behaviour
  of Linux and Solaris.
  
  The old code is left in place, should anyone need it, guarded
  by #ifdef NS_REREAD_CONF.
  
  Reviewed by:	imp, bcr
  MFC after:	2 weeks
  Relnotes:	yes
  Sponsored by:	DARPA, AFRL
  Differential Revision:	https://reviews.freebsd.org/D17934

Modified:
  head/lib/libc/net/nsdispatch.c
  head/share/man/man5/nsswitch.conf.5

Modified: head/lib/libc/net/nsdispatch.c
==============================================================================
--- head/lib/libc/net/nsdispatch.c	Sat Nov 10 22:14:09 2018	(r340338)
+++ head/lib/libc/net/nsdispatch.c	Sat Nov 10 23:07:46 2018	(r340339)
@@ -335,6 +335,7 @@ static int
 nss_configure(void)
 {
 	static time_t	 confmod;
+	static int	 already_initialized = 0;
 	struct stat	 statbuf;
 	int		 result, isthreaded;
 	const char	*path;
@@ -352,6 +353,16 @@ nss_configure(void)
 	if (path == NULL)
 #endif
 		path = _PATH_NS_CONF;
+#ifndef NS_REREAD_CONF
+	/*
+	 * Define NS_REREAD_CONF to have nsswitch notice changes
+	 * to nsswitch.conf(5) during runtime.  This involves calling
+	 * stat(2) every time, which can result in performance hit.
+	 */
+	if (already_initialized)
+		return (0);
+	already_initialized = 1;
+#endif /* NS_REREAD_CONF */
 	if (stat(path, &statbuf) != 0)
 		return (0);
 	if (statbuf.st_mtime <= confmod)

Modified: head/share/man/man5/nsswitch.conf.5
==============================================================================
--- head/share/man/man5/nsswitch.conf.5	Sat Nov 10 22:14:09 2018	(r340338)
+++ head/share/man/man5/nsswitch.conf.5	Sat Nov 10 23:07:46 2018	(r340339)
@@ -33,7 +33,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 6, 2016
+.Dd November 10, 2018
 .Dt NSSWITCH.CONF 5
 .Os
 .Sh NAME
@@ -340,6 +340,12 @@ sets a policy of "if the user is notfound in nis, do n
 This treats nis as the authoritative source of information, except
 when the server is down.
 .Sh NOTES
+The
+.Nm
+file is parsed by each program only once.
+Subsequent changes will not be applied until the program
+is restarted.
+.Pp
 If system got compiled with
 .Va WITHOUT_NIS
 you have to remove



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