7.5.4. How Compiling and Linking Affects the Speed of MySQL
Most of the following tests were performed on Linux with the
MySQL benchmarks, but they should give some indication for other
operating systems and workloads.
You obtain the fastest executables when you link with
-static.
On Linux, it is best to compile the server with
pgcc and -O3. You need about
200MB memory to compile sql_yacc.cc with
these options, because gcc or
pgcc needs a great deal of memory to make all
functions inline. You should also set CXX=gcc
when configuring MySQL to avoid inclusion of the
libstdc++ library, which is not needed. Note
that with some versions of pgcc, the
resulting binary runs only on true Pentium processors, even if
you use the compiler option indicating that you want the
resulting code to work on all x586-type processors (such as
AMD).
By using a better compiler and compilation options, you can
obtain a 10–30% speed increase in applications. This is
particularly important if you compile the MySQL server yourself.
When we tested both the Cygnus CodeFusion and Fujitsu compilers,
neither was sufficiently bug-free to allow MySQL to be compiled
with optimizations enabled.
The standard MySQL binary distributions are compiled with
support for all character sets. When you compile MySQL yourself,
you should include support only for the character sets that you
are going to use. This is controlled by the
--with-charset option to
configure.
Here is a list of some measurements that we have made:
If you use pgcc and compile everything
with -O6, the mysqld
server is 1% faster than with gcc 2.95.2.
If you link dynamically (without -static),
the result is 13% slower on Linux. Note that you still can
use a dynamically linked MySQL library for your client
applications. It is the server that is most critical for
performance.
For a connection from a client to a server running on the
same host, if you connect using TCP/IP rather than a Unix
socket file, performance is 7.5% slower. (On Unix, if you
connect to the hostname localhost, MySQL
uses a socket file by default.)
For TCP/IP connections from a client to a server, connecting
to a remote server on another host is 8–11% slower
than connecting to a server on the same host, even for
connections over 100Mb/s Ethernet.
When running our benchmark tests using secure connections
(all data encrypted with internal SSL support) performance
was 55% slower than with unencrypted connections.
If you compile with --with-debug=full, most
queries are 20% slower. Some queries may take substantially
longer; for example, the MySQL benchmarks run 35% slower. If
you use --with-debug (without
=full), the speed decrease is only 15%.
For a version of mysqld that has been
compiled with --with-debug=full, you can
disable memory checking at runtime by starting it with the
--skip-safemalloc option. The execution
speed should then be close to that obtained when configuring
with --with-debug.
On a Sun UltraSPARC-IIe, a server compiled with Forte 5.0 is
4% faster than one compiled with gcc 3.2.
On a Sun UltraSPARC-IIe, a server compiled with Forte 5.0 is
4% faster in 32-bit mode than in 64-bit mode.
Compiling with gcc 2.95.2 for UltraSPARC
with the -mcpu=v8 -Wa,-xarch=v8plusa
options gives 4% more performance.
On Solaris 2.5.1, MIT-pthreads is 8–12% slower than
Solaris native threads on a single processor. With greater
loads or more CPUs, the difference should be larger.
Compiling on Linux-x86 using gcc without
frame pointers (-fomit-frame-pointer or
-fomit-frame-pointer -ffixed-ebp) makes
mysqld 1–4% faster.
Binary MySQL distributions for Linux that are provided by MySQL
AB used to be compiled with pgcc. We had to
go back to regular gcc due to a bug in
pgcc that would generate binaries that do not
run on AMD. We will continue using gcc until
that bug is resolved. In the meantime, if you have a non-AMD
machine, you can build a faster binary by compiling with
pgcc. The standard MySQL Linux binary is
linked statically to make it faster and more portable.
