Philip M. Gollucci wrote:
Philip M. Gollucci wrote:
my.cnf
innodb_thread_concurrency = 8
You want '0' or performance will suck. There's a basic architectural
flaw in how mysql handles non-zero concurrency values here (innodb
accesses are serialized by a global mutex that protects a counter to
check if it should try to allow more innodb concurrency. Duh.)
Anyway, assuming your disks can keep up you should see a big performance
boost when you switch to 7.0. This is a fairly big "if" though: I don't
know if it's even feasible for a write-heavy database to saturate 8 CPUs
instead of being bottlenecked by disk speeds and leaving the CPUs mostly
from /usr/local/share/my-innodb-heavy-4G.cnf
# This permits the application to give the threads system a hint for the
# desired number of threads that should be run at the same time. This
# value only makes sense on systems that support the
# thread_concurrency()
# function call (Sun Solaris, for example).
# You should try [number of CPUs]*(2..4) for thread_concurrency
thread_concurrency = 8
# Number of IO threads to use for async IO operations. This value is
# hardcoded to 4 on Unix, but on Windows disk I/O may benefit from a
# larger number.
innodb_file_io_threads = 4
# Number of threads allowed inside the InnoDB kernel. The optimal value
# depends highly on the application, hardware as well as the OS
# scheduler properties. A too high value may lead to thread thrashing.
innodb_thread_concurrency = 16
Apparently its only set in this file.
We should probably submit a bug to MySQL rather then add a patch to
ports or do both and remove the ports when its released.
I believe the performance bug is well known actually, at least to the
www.mysqlperformanceblog.com people which is where I got my test config
from. I discovered the reason for it recently when I accidentally ran
with a default config (innodb_thread_concurrency defaulted to 8 for me)
and spent some time tracking down why performance was terrible until I
set it back to 0.
Kris
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