Date: Fri, 21 May 2004 22:23:00 -0700 From: JG <amd64list@jpgsworld.com> To: freebsd-threads@freebsd.org Subject: Re: Why is MySQL nearly twice as fast on Linux? Message-ID: <5.2.0.9.2.20040521215952.0166c368@mail.ojoink.com> In-Reply-To: <Pine.GSO.4.10.10405212355001.18976-100000@pcnet5.pcnet.com > References: <5.2.0.9.2.20040521154458.01627688@127.0.0.1>
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>After reading the posts at the mailing lists mentioned above, >Do you have any suggestions or ideas as to what the problem is? >We are more concerned about correctness right now than speed. >There are some optimizations that can be made WRT low-level >locking (for instance using cmpxchg when possible). The >kernel also still has some more work WRT locking. > >Also, the default kernel configuration with WITNESS and >INVARIANTS adds overhead. As stated in the benchmark results, WITNESS and INVARIANTS was disabled. Someone else brought that up very early on. >Yet another also, MySQL uses scope system threads by default >instead of scope process threads. Scope process threads seem >to perform better. > > http://people.freebsd.org/~deischen/mysql40-server.diffs Again, this patch was already made. It did next to nothing performance wise for MySQL. >You can also build mysql with LinuxThreads under FreeBSD >and see if it performs any better. LinuxThreads is not available for FreeBSD/AMD64. However, as reported on the freebsd-amd64 thread list archive, sadly, the best configuration turned out to be running this 64-bit AMD64 hardware in 32-bit mode under _i386_ FreeBSD rather than FreeBSD/AMD64 with mysql compiled with linuxthreads -- and those results were still very poor compared to a "out of the box" Linux + mysql install. > If it is comparable, >that would tend to point to the kernel as the limiting >factor. There is a significant improvement when using LinuxThreads vs libpthreads or libc_r, others have reported no difference with libthr as well.
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