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                              WORKLOG TASK
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TASK...........: Partitioned Key Cache for MyISAM
CREATION DATE..: Sun, 14 Feb 2010, 00:09
SUPERVISOR.....: Monty
IMPLEMENTOR....: 
COPIES TO......: Igor, Monty, Sergei
CATEGORY.......: Server-BackLog
TASK ID........: 84 (http://askmonty.org/worklog/?tid=84)
VERSION........: Benchmarks-3.0
STATUS.........: Assigned
PRIORITY.......: 60
WORKED HOURS...: 0
ESTIMATE.......:  (hours remain)
ORIG. ESTIMATE.: 0

PROGRESS NOTES:

-=-=(Igor - Tue, 16 Mar 2010, 19:28)=-=-
High Level Description modified.
--- /tmp/wklog.84.old.22253     2010-03-16 19:28:09.000000000 +0000
+++ /tmp/wklog.84.new.22253     2010-03-16 19:28:09.000000000 +0000
@@ -1,18 +1 @@
-A partitioned key cache is a collection of structures for regular MyiSAM key
-caches called key cache partitions. Any page from a file can be placed into a
-buffer of only one partition. The number of the partition is calculated from the
-file number and the position of the page in the file, and it's always the same
-for the page. The function that maps pages into partitions takes care of even
-distribution of pages among partitions.
 
-Partition key cache mitigate one of the major problem of simple key cache:
-thread contention for key cache lock (mutex). Every call of a key cache
-interface function must acquire this lock. So threads compete for this lock even
-in the case when they have acquired shared locks for the file and pages they
-want read from are in the key cache buffers. When working with a partitioned key
-cache any key cache interface function that needs only one page has to acquire
-the key cache lock only for the partition the page is ascribed to. This makes
-the chances for threads not compete for the same key cache lock better.
-
-The idea and the original of the partitioned key cache was provided by one of
-our external contributers.



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