Why is MySQL nearly twice as fast on Linux?

[David Xu]

I suggest you to do file system benchmark first,  I suspect
-CURRENT file system's performance is far behind than Linux.

David Xu


JG wrote:

>
>
> >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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