----------------------------------------------------------------------- WORKLOG TASK -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 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. DESCRIPTION: ESTIMATED WORK TIME ESTIMATED COMPLETION DATE ----------------------------------------------------------------------- WorkLog (v3.5.9)