… constantly referring to the amazing MySQL manual, especially the option and variable reference table. But…sysdate_is_nowblogpercona.commanual system_time_zoneblogpercona.commanual table_definition_cacheblogpercona.commanual table_lock_wait_timeoutblogpercona.commanual Table_locks_…
Post: Modeling MySQL Capacity by Measuring Resource Consumptions
March 8, 2011 By 1 Comment
… ? You can take a look at procfs for MySQL process: root@ubuntu:/var/log/mysql# cat /proc/19018/stat 19018 (mysqld) S… TIME” here, subtracting CPU time from it we get “Wait Time” which is in this case 775-49=726 seconds or 4005us per select. Wait time… between Wait Time and CPU time is very helpful to see how “wait free your system is”. If it system is already have low wait…
Post: Understand InnoDB spin waits, win a Percona Live ticket
September 2, 2011 By 2 Comments
… it waited in a spin-wait. rounds 19812448 is the number of times threads looped in the spin-wait cycle, checking the mutex. OS waits 375285 is the number of times the thread gave up spin-waiting… has ended. Don’t miss your opportunity to learn about MySQL in London from world-famous experts!
Post: Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit
November 24, 2011 By 2 Comments
…. Now, Valgrind does not need much introduction, especially to the MySQL server developers. The Valgrind Memcheck tool, which is synonymous with… a selected MTR testcase under Helgrind. (For the time being, running the whole MySQL testsuite is not very practical due to 100x…_io_complete (sync0sync.ic:150) ==9090== by 0x6B34515: fil_aio_wait (fil0fil.c:4512) ==9090== by 0x6BC58E0: io_handler_thread (srv0start…
Post: Scaling problems still exist in MySQL 5.5 and Percona Server 5.5
May 20, 2011 By 11 Comments
… in Percona Server 5.5 showing up to 2.5 times better performance or 150%, which is a great headline numbers…_command,mysql_parse,dispatch_command,do_command,do_handle_one_conn ection,handle_one_connection,start_thread,clone 4 pthread_cond_wait…_command,mysql_parse,dispatch_command,do_command,do_handle_one_conn ection,handle_one_connection,start_thread,clone 2 pthread_cond_wait…
Post: Apache PHP MySQL and Runaway Scripts
May 20, 2008 By 20 Comments
… different behavior for scripts running very long time. For simplicity I did not use MySQL, but other system call – sleep() which has… much more useful for scripts which spend most of their time waiting. There is also pcntl_signal function which you can use… 2 simple scripts which run for 1000 seconds (spending this time on MySQL time) one is doing single query another 1000 queries 1…
Post: How to debug long-running transactions in MySQL
March 8, 2011 By 6 Comments
… very long time without committing, and has modified data, then other transactions could block and fail with a lock wait timeout. The…)”>&2 exit 1 fi host=$(mysql -ss -e ‘SELECT p.HOST FROM information_schema.innodb_lock_waits w INNER JOIN information_schema… worst queries together. This has worked for me a few times. Alas, there are some cases where it won’t work…
Post: How Does Semisynchronous MySQL Replication Work?
January 19, 2012 By 24 Comments
…until all replicas have also committed successfully. In MySQL‘s semi-synchronous replication, the commit completes before…transaction to its own data, and during that time, it will be delayed relative to the master….but a crash occurs while the master is waiting for acknowledgment from a slave, it is …
Post: How Percona diagnoses MySQL server stalls
March 3, 2011 By 6 Comments
…, the collect tool makes it easy to gather snapshots of waiting (stack traces) and CPU consumption (oprofile). That’s important because… finish these, I’ll post them on Percona.TV, our MySQL video/screencast blog site. Another interesting topic is how to… that can cause a stall in MySQL, and they usually begin microscopically and get worse over time, sometimes abruptly worse. I’ll…
Post: MySQL 5.5 and MySQL 5.6 default variable values differences
February 21, 2013 By 8 Comments
…_ON_METADATA | ON | OFF | | PERFORMANCE_SCHEMA_EVENTS_WAITS_HISTORY_SIZE | 10 | 5 | | PERFORMANCE_SCHEMA_EVENTS_WAITS_HISTORY_LONG_SIZE | 10000 | 100 | | PERFORMANCE…_SCHEMA_MAX_THREAD_INSTANCES | 1000 | 224 | | SOCKET | /tmp/mysql_sandbox5530.sock | /tmp/mysql_sandbox5610.sock | | INNODB_FILE_PER_TABLE | OFF | ON | | SYNC… far as MySQL 5.6 goes – STRICT_MODE and other safer behaviors are not enabled by default. innodb_old_blocks_time now…
