mirror of
https://github.com/MariaDB/server.git
synced 2025-01-31 02:51:44 +01:00
MariaDB server is a community developed fork of MySQL server. Started by core members of the original MySQL team, MariaDB actively works with outside developers to deliver the most featureful, stable, and sanely licensed open SQL server in the industry.
amazon-web-servicesdatabasefulltext-searchgalerageographical-information-systeminnodbjsonmariadbmysqlrdbmsrelational-databasessqlstorage-enginevector-database
e405ab1626
The problem is that MySQL's 'fast' mutex implementation uses the random() routine to determine the spin delay. Unfortunately, the routine interface is not thead-safe and some implementations (eg: glibc) might use a internal lock to protect the RNG state, causing excessive locking contention if lots of threads are spinning on a MySQL's 'fast' mutex. The code was also misusing the value of the RAND_MAX macro, this macro represents the largest value that can be returned from the rand() function, not random(). The solution is to use the quite simple Park-Miller random number generator. The initial seed is set to 1 because the previously used generator wasn't being seeded -- the initial seed is 1 if srandom() is not called. Futhermore, the 'fast' mutex implementation has several shortcomings and provides no measurable performance benefit. Therefore, its use is not recommended unless it provides directly measurable results. include/my_pthread.h: Add field to keep the RNG state. mysys/thr_mutex.c: Use a palliative per-mutex rng state to determine the spin delay. The RNG is not thread-safe but jumping a few sequences in the RNG is harmless. |
||
|---|---|---|
| .bzr-mysql | ||
| BitKeeper | ||
| BUILD | ||
| client | ||
| cmd-line-utils | ||
| config/ac-macros | ||
| dbug | ||
| Docs | ||
| extra | ||
| include | ||
| libmysql | ||
| libmysql_r | ||
| libmysqld | ||
| man | ||
| mysql-test | ||
| mysys | ||
| netware | ||
| plugin | ||
| pstack | ||
| regex | ||
| scripts | ||
| server-tools | ||
| sql | ||
| sql-bench | ||
| sql-common | ||
| storage | ||
| strings | ||
| support-files | ||
| tests | ||
| unittest | ||
| vio | ||
| win | ||
| zlib | ||
| .bzrignore | ||
| .cvsignore | ||
| CMakeLists.txt | ||
| configure.in | ||
| COPYING | ||
| EXCEPTIONS-CLIENT | ||
| INSTALL-SOURCE | ||
| INSTALL-WIN-SOURCE | ||
| Makefile.am | ||
| README | ||
This is a release of MySQL, a dual-license SQL database server. MySQL is brought to you by the MySQL team at MySQL AB. License information can be found in these files: - For GPL (free) distributions, see the COPYING file and the EXCEPTIONS-CLIENT file. - For commercial distributions, see the LICENSE.mysql file. For further information about MySQL or additional documentation, see: - The latest information about MySQL: http://www.mysql.com - The current MySQL documentation: http://dev.mysql.com/doc Some manual sections of special interest: - If you are migrating from an older version of MySQL, please read the "Upgrading from..." section first! - To see what MySQL can do, take a look at the features section. - For installation instructions, see the Installing and Upgrading chapter. - For the new features/bugfix history, see the Change History appendix. - For the currently known bugs/misfeatures (known errors) see the Problems and Common Errors appendix. - For a list of developers and other contributors, see the Credits appendix. A local copy of the MySQL Reference Manual can be found in the Docs directory in GNU Info format. You can also browse the manual online or download it in any of several formats at the URL given earlier in this file. ************************************************************ IMPORTANT: Bug or error reports should be sent to http://bugs.mysql.com.