Latch, mutex and beyond

May 22, 2011

MEDIAS-2011

Filed under: Conference,DTrace,Latch,Latch Statistics,Theory,_spin_count — andreynikolaev @ 1:56 pm

A week ago I returned from MEDIAS-2011 conference, which was held in Limassol (Cyprus). It was an exciting experience to speak at general Computer Science conference. This was also an opportunity to discuss topics beyond the usual scope of Oracle conferences and see non addicted to Oracle point of view.

As you may expect, my presentation was entitled “Exploring the Oracle latches”. You can download it here. The presentation contains more math and less X$ materials than usual. Also, I added several introductory slides about Oracle, its performance and tuning.

And, of course, Cyprus is a great place!

Thanks to Professor S.V. Klimenko for kindly inviting me to MEDIAS 2011 conference.
Thanks to RDTEX CEO I.G. Kunitsky for financial support.
Thanks to RDTEX Technical Support Centre Director S.P. Misiura for years of encouragement and support of my investigations.

May 1, 2011

Divide and conquer the “true” mutex contention

Filed under: 11.2,Contention,Mutex,Patches — andreynikolaev @ 7:16 pm

Oracle 11.2.0.2 contains enhancements 9282521 and 9239863 named ‚ÄúLibrary cache: mutex X” for objects highly contended for. Part I and II. These enhancements introduce new interesting possibilities to tune some types of the mutex contention.

Contention for heavily accessed objects can now be divided between multiple copies of object in the library cache. According to notes 9282521.8 and 9239863.8 describing the patches, the enhancements should be used:
When there is true contention on a specific library cache object….
Let me investigate this deeper. I will use Oracle 11.2.0.2.2 for Solaris SPARC (64-bit) on 8Cores/32Threads Sun Fire T2000. I chose this platform in order to emphasize how the enhancements work. (more…)

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