martin 98/04/15 05:21:46
Modified: htdocs/manual/misc perf.html
Log:
Add notice about some inefficient SVR4 implementations of time zones in gettimeofday()
Revision Changes Path
1.20 +49 -0 apache-1.3/htdocs/manual/misc/perf.html
Index: perf.html
===================================================================
RCS file: /home/cvs/apache-1.3/htdocs/manual/misc/perf.html,v
retrieving revision 1.19
retrieving revision 1.20
diff -u -u -r1.19 -r1.20
--- perf.html 1998/02/05 20:04:30 1.19
+++ perf.html 1998/04/15 12:21:45 1.20
@@ -30,6 +30,7 @@
<LI><A HREF="#Linux">Linux</A>
<LI><A HREF="#Solaris">Solaris</A>
<LI><A HREF="#SunOS">SunOS 4.x</A>
+<LI><A HREF="#SVR4">SVR4</A>
</UL>
<HR>
@@ -117,6 +118,54 @@
More information on tuning SOMAXCONN on SunOS can be found at
<A HREF="http://www.islandnet.com/~mark/somaxconn.html">
http://www.islandnet.com/~mark/somaxconn.html</A>.
+
+<P><HR>
+
+<H3><A NAME="SVR4">
+SVR4
+</A></H3>
+
+Some SVR4 versions waste three system calls on every
+<SAMP>gettimeofday()</SAMP> call. Depending on the syntactic
+form of the <SAMP>TZ</SAMP> environment variable, these
+systems have several different algorithms to determine the
+local time zone (presumably <EM>compatible</EM> with
+something). The following example uses the central european
+time zone to demonstrate this:
+<DL>
+ <DT><STRONG>TZ=:MET</STRONG>
+ <DD>This form delegates the knowledge of the time zone
+ information to an external compiled zoneinfo file
+ (à la BSD).<BR>
+ <STRONG>Caveat:</STRONG> Each time the gettimeofday()
+ function is called, the external zone info is read in
+ again (at least on some SVR4 systems). That results in
+ three wasted system calls with every apache request
+ served.<PRE>
+ open("/usr/lib/locale/TZ/MET", O_RDONLY) = 3
+ read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 7944) = 778
+ close(3) = 0</PRE>
+
+ <DT><STRONG>TZ=MET-1MDT,M3.5.0/02:00:00,M10.5.0/03:00:00</STRONG>
+ <DD>This syntax form (à la SYSV) contains all the
+ knowledge about time zone beginning and ending times in
+ its external representation. It has to be parsed each
+ time it is evaluated, resulting in a slight computing
+ overhead, but it requires no system call. Though the
+ table lookup à la BSD is the more sophisticated
+ technical solution, the bad SVR4 implementation makes
+ this the preferred syntax on systems which otherwise
+ access the external zone info file repeatedly.
+</DL>
+You should use the <SAMP>truss</SAMP> utility on a
+single-process apache server (started with the <SAMP>-X</SAMP>
+debugging switch) to determine whether your system can profit
+from the second form of the <SAMP>TZ</SAMP> environment
+variable. If it does, you could integrate the setting of the
+preferred <SAMP>TZ</SAMP> syntax into the httpd startup
+script, which is usually simply a copy of (or symbolic link
+to) the <SAMP>apachectl</SAMP> utility script, or into the
+system's <SAMP>/etc/TIMEZONE</SAMP> script.
<P><HR>
Modified: htdocs/manual/misc perf.html
Log:
Add notice about some inefficient SVR4 implementations of time zones in gettimeofday()
Revision Changes Path
1.20 +49 -0 apache-1.3/htdocs/manual/misc/perf.html
Index: perf.html
===================================================================
RCS file: /home/cvs/apache-1.3/htdocs/manual/misc/perf.html,v
retrieving revision 1.19
retrieving revision 1.20
diff -u -u -r1.19 -r1.20
--- perf.html 1998/02/05 20:04:30 1.19
+++ perf.html 1998/04/15 12:21:45 1.20
@@ -30,6 +30,7 @@
<LI><A HREF="#Linux">Linux</A>
<LI><A HREF="#Solaris">Solaris</A>
<LI><A HREF="#SunOS">SunOS 4.x</A>
+<LI><A HREF="#SVR4">SVR4</A>
</UL>
<HR>
@@ -117,6 +118,54 @@
More information on tuning SOMAXCONN on SunOS can be found at
<A HREF="http://www.islandnet.com/~mark/somaxconn.html">
http://www.islandnet.com/~mark/somaxconn.html</A>.
+
+<P><HR>
+
+<H3><A NAME="SVR4">
+SVR4
+</A></H3>
+
+Some SVR4 versions waste three system calls on every
+<SAMP>gettimeofday()</SAMP> call. Depending on the syntactic
+form of the <SAMP>TZ</SAMP> environment variable, these
+systems have several different algorithms to determine the
+local time zone (presumably <EM>compatible</EM> with
+something). The following example uses the central european
+time zone to demonstrate this:
+<DL>
+ <DT><STRONG>TZ=:MET</STRONG>
+ <DD>This form delegates the knowledge of the time zone
+ information to an external compiled zoneinfo file
+ (à la BSD).<BR>
+ <STRONG>Caveat:</STRONG> Each time the gettimeofday()
+ function is called, the external zone info is read in
+ again (at least on some SVR4 systems). That results in
+ three wasted system calls with every apache request
+ served.<PRE>
+ open("/usr/lib/locale/TZ/MET", O_RDONLY) = 3
+ read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 7944) = 778
+ close(3) = 0</PRE>
+
+ <DT><STRONG>TZ=MET-1MDT,M3.5.0/02:00:00,M10.5.0/03:00:00</STRONG>
+ <DD>This syntax form (à la SYSV) contains all the
+ knowledge about time zone beginning and ending times in
+ its external representation. It has to be parsed each
+ time it is evaluated, resulting in a slight computing
+ overhead, but it requires no system call. Though the
+ table lookup à la BSD is the more sophisticated
+ technical solution, the bad SVR4 implementation makes
+ this the preferred syntax on systems which otherwise
+ access the external zone info file repeatedly.
+</DL>
+You should use the <SAMP>truss</SAMP> utility on a
+single-process apache server (started with the <SAMP>-X</SAMP>
+debugging switch) to determine whether your system can profit
+from the second form of the <SAMP>TZ</SAMP> environment
+variable. If it does, you could integrate the setting of the
+preferred <SAMP>TZ</SAMP> syntax into the httpd startup
+script, which is usually simply a copy of (or symbolic link
+to) the <SAMP>apachectl</SAMP> utility script, or into the
+system's <SAMP>/etc/TIMEZONE</SAMP> script.
<P><HR>