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Showing entries 1 to 9

Displaying posts with tag: mutex (reset)

Log Buffer #429: A Carnival of the Vanities for DBAs
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This Log Buffer Edition gathers a wide sample of blogs and then purifies the best ones from Oracle, SQL Server and MySQL.

Oracle:

  • If you take a look at the “alter user” command in the old 9i documentation, you’ll see this: DEFAULT ROLE Clause.
  • There’s been an interesting recent discussion on the OTN Database forum regarding “Index blank …
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Getting mutex information from MySQL’s performance_schema
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We have been using SHOW ENGINE INNODB MUTEX command for years. It shows us mutex and rw-lock information that could be useful during service troubleshooting in case of performance problems. As Morgan Tocker announced in his blog post the command will be removed from MySQL 5.7 and we have to use performance_schema to get that info.

The documentation of MySQL also says that most of the command output has been removed from 5.6 and that we can find similar info in performance_schema. It doesn’t show any …

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Update on MySQL on POWER8
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About 1.5 months ago I blogged on MySQL 5.6 on POWER andtalked about what I had to poke at to make modern MySQL versions run and run well on shiny POWER8 systems.

One of those bugs, MySQL bug 47213 (InnoDB mutex/rw_lock should be conscious of memory ordering other than Intel) was recently marked as CLOSED by the Oracle MySQL team and the upcoming 5.6.20 and 5.7.5 releases should have the fix!

This is excellent news for those wanting to run MySQL on SMP systems …

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1 million SQL Queries Per Second: MySQL 5.7 on POWER8
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I’ve previously covered MySQL 5.6 on POWER (with patch), MySQL 5.6 Performance on POWER8 (spoiler: new performance record) and MySQL 5.7 on POWER.

Of course, The postings on this site are my own and don’t necessarily …

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InnoDB scalability issues due to tables without primary keys
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Each day there is probably work done to improve performance of the InnoDB storage engine and remove bottlenecks and scalability issues. Hence there was another one I wanted to highlight:

Scalability issues due to tables without primary keys

This scalability issue is caused by the usage of tables without primary keys. This issue typically shows itself as contention on the InnoDB dict_sys mutex. Now the dict_sys mutex controls access to the data dictionary. This mutex is used at various places. I will only mention a few of them:

  • During operations such as opening and closing table handles, or
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Why I am So Excited About the MySQL Performance Schema
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The improved Performance Schema in MySQL 5.6 provides a new way of investigating issues in the database. Many issues that previously required tools such as strace, dtrace, etc. can now be investigated directly from inside MySQL in a platform independent way using standard SQL statements.

The Performance Schema is enabled by default starting from the latest milestone release, 5.6.6. You have instruments which are the things you can measure, and consumers which are those that use the measurements. Not all instruments and consumers are enabled out of the box, however once the plugin is enabled, individual instruments and consumers can …

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MySQL 5.5: InnoDB Performance Improvements on Windows
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At MySQL, we know our users want Performance, Scalability, Reliability, and Availability, regardless of the platform the choose to deploy. We have always had excellent benchmarks on Linux, and with MySQL 5.5, we are also working hard on improving performance on Windows.

The original patch of improving Windows performance was developed by MySQL senior developer Vladislav Vaintroub; benchmarks by QA engineer Jonathan Miller. We integrated the patch into MySQL 5.5 release.

The following two charts show the comparison of MySQL 5.5 vs. MySQL 5.1 (plugin) vs. MySQL 5.1 (builtin) using sysbench:

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A growing trend: InnoDB mutex contention
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I’ve been noticing an undeniable trend in my consulting engagements in the last year or so, and when I vocalized this today, heads nodded all around me. Everyone sees a growth in the number of cases where otherwise well-optimized systems are artificially limited by InnoDB contention problems.

A year ago, I simply wasn’t seeing the need for analysis of GDB backtraces en masse. These days, I’m writing custom tools to gather and analyze backtraces. A year ago, I simply looked at the SEMAPHORE section of SHOW INNODB STATUS. These days I’m writing custom tools to aggregate and reformat that data so I can interpret it more easily. And I’m …

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Software is Hard Sometimes …
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Some months ago, Google released a patch for InnoDB that boosts performance on multi-core servers. We decided to incorporate the change into the InnoDB Plugin to make everybody happy: users of InnoDB don’t have to apply the patch, and Google no longer has to maintain the patch for new versions of InnoDB. And it makes us at Innobase happy because it improves our product (as you can in this post about InnoDB Plugin release 1.0.3).

However, there are always …

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Showing entries 1 to 9

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