Some Query Cache fixups.

Added info about two new Query Cache status variables.

Docs/manual.texi

@@ -35523,11 +35523,11 @@ dynamic content.
 
 Following are some performance data for the query cache
 (We got these by running the MySQL benchmark suite on a Linux Alpha
-2x500 MHz with 2GB RAM and a 64MB query cache).
+2x500 MHz with 2GB RAM and a 64MB query cache):
 
 @itemize @bullet
 @item
-If want to disable the query cache code set @code{query_cache_size=0}.
+If you want to disable the query cache code set @code{query_cache_size=0}.
 By disabling the query cache code there is no noticeable overhead.
 @item
 If all of the queries you're preforming are simple (such as selecting a
@@ -35578,7 +35578,7 @@ found rows is also stored in the cache.
 If a table changes (@code{INSERT}, @code{UPDATE}, @code{DELETE},
 @code{TRUNCATE}, @code{ALTER} or @code{DROP TABLE|DATABASE}),
 then all cached queries that used this table (possibly through a
-MRG_MyISAM table!) become invalid and are removed from the cache.
+@code{MRG_MyISAM} table!) become invalid and are removed from the cache.
 
 Currently all @code{InnoDB} tables are invalidated on @code{COMMIT},
 in the future this will be changed so only tables changed in the
@@ -35695,18 +35695,30 @@ You can monitor query cache performance in @code{SHOW STATUS}:
 @item @code{Qcache_inserts}
  @tab Number of queries added to the cache.
 @item @code{Qcache_hits}
- @tab Number of cache hits
+ @tab Number of cache hits.
 @item @code{Qcache_not_cached}
  @tab Number of non-cached queries
- (not cachable, or due to SQL_QUERY_CACHE_TYPE)
+ (not cachable, or due to @code{SQL_QUERY_CACHE_TYPE}).
 @item @code{Qcache_free_memory}
  @tab Amount of free memory for query cache.
+@item @code{Qcache_total_blocks}
+ @tab Total number of blocks in query cache.
+@item @code{Qcache_free_blocks}
+ @tab Number of free memory blocks in query cache.
 @end multitable
 
-Please note:
 Total number of queries =
 @code{Qcache_inserts} + @code{Qcache_hits} + @code{Qcache_not_cached}.
 
+The query cache uses variable length blocks, so @code{Qcache_total_blocks}
+and @code{Qcache_free_blocks} may indicate query cache memory fragmentation.
+After @code{FLUSH QUERY CACHE} only a single (big) free block remains.
+
+Note: Every query needs a minimum of two blocks (one for the query text
+and one or more for the query results). Also, every table that is used
+by a query needs one block, but if two or more queries use same table
+only one block needs to be allocated.
+
 
 @node Table types, Clients, Reference, Top
 @chapter MySQL Table Types