Aria engine does not start with --maria-pagecache-buffer-size=128K --maria-block-size={16K,32K}

[Philip Stoev]

The Aria engine does not start with --maria-pagecache-buffer-size=128K --maria-block-size={16K,32K} . This prevents this particular combination of values (low page cache, large pages) to be tested.

To repeat:

 MTR_VERSION=1 perl mysql-test-run.pl --mysqld=--maria-pagecache-buffer-size=128K --start-and-exit 1st --mysqld=--maria-block-size=16K

the error log says:

110226 18:38:40 [ERROR] mysqld: Not enough memory to allocate 8 pagecache pages
110226 18:38:40 [ERROR] Plugin 'MARIA' init function returned error.
110226 18:38:40 [ERROR] Plugin 'MARIA' registration as a STORAGE ENGINE failed.

[Philip Stoev (pstoev-askmonty)]

16K pages work with 256K cache
32K pages work with 512K cache

However, testing with 128K cache would produce a higher number of cache misses and disk I/O.

[Michael Widenius (monty)]

This is as expected. Aria needs at least 8 full blocks to work reliable. The reason that 128K is not enough is that some part of the page cache memory goes to managing the blocks.

Fix: use --aria-block-size=16K --aria-pagecache-buffer-size=140K