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LRU dump

LRU followup #2

As I wrote in the previous LRU followup the innodb_lru_dump_restore directive has the drawback that it only loads the LRU dumpfile after starting up. I’m happy to say that I’m not the only one who noticed that: Vadim Tkachenko noticed the same a few months back when he was integrating Galera replication and he filed a bugreport for it.

It now has been resolved as of Percona Server 5.1.59-13.0 and 5.5.16-22.0 (both released this morning) with the configuration directive innodb-blocking-lru-restore.

However the bugreport states there are two different directived: innodb-blocking-lru-restore (5.1) and innodb-blocking-buffer-pool-restore (5.5). Just tested it on our test machine and the latter is the correct directive and probably the release notes of the 5.5 release were copied from the 5.1 release. I’ve just commented this in the 5.5 release post, so I think it will be corrected soon.

The directive works as it should: during the InnoDB initialization it loads the LRU dump:

mysqld: 111017 10:13:12 InnoDB: Completed initialization of buffer pool
mysqld: 111017 10:13:12 InnoDB: highest supported file format is Barracuda.
mysqld: 111017 10:13:12 InnoDB: Restoring buffer pool pages from ib_lru_dump
mysqld: 111017 10:13:12 InnoDB: Waiting for the background threads to start

Works like a charm and I’m very happy with this change. :)
Of course the LRU dump of our test machine is very small (512MB bufferpool) so it was loaded instantly. On a normal machine it should take a bit longer…

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About Art van Scheppingen

Head of Database Engineering at Spil Games

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