bk commit into 5.0 tree (cmiller:1.2423) BUG#27501

[Chad MILLER]

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5.0 repository of cmiller. When cmiller does a push these changes will
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ChangeSet@stripped, 2007-03-28 21:21:34-04:00, cmiller@stripped +2 -0
  Bug#27501: 5.0 significantly more sys ("kernel") time than 4.1 \
  	due to getrusage() calls
  
  Even if profiling is turned off, the parser makes calls to reset 
  the state at the beginning of each query.  That would eventually 
  instantiate a PROFILE_ENTRY, which does indeed capture resource 
  usage.
  
  Instead, now check that profiling is active before progressing
  far into the storage/expiration of old entries in the history.
  This has the pleasant side-effect that queries to toggle profiling
  are not recorded in the history.

  mysql-test/r/profiling.result@stripped, 2007-03-28 21:21:33-04:00, cmiller@stripped +1 -1
    Now after we turn off profiling, the beginning of the next query 
    refuses to enter the profiling code and it discards the info.

  sql/sql_profile.cc@stripped, 2007-03-28 21:21:33-04:00, cmiller@stripped +11 -0
    Add the same condition twice:  Once to abort storing previous 
    query information and the other to abort initialization for this 
    query that is starting.
    
    We do this symmetrically, before and after expiring old history 
    entries, so that the counts are correct.

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	cmiller
# Host:	zippy.cornsilk.net
# Root:	/home/cmiller/work/mysql/mysql-5.0-comeng

--- 1.3/mysql-test/r/profiling.result	2007-03-27 10:31:28 -04:00
+++ 1.4/mysql-test/r/profiling.result	2007-03-28 21:21:33 -04:00
@@ -248,6 +248,7 @@
 12
 show profiles;
 Query_ID	Duration	Query
+15	#	select count(*) from t1
 16	#	insert into t1 select * from t1
 17	#	insert into t1 select * from t1
 18	#	insert into t1 select * from t1
@@ -277,7 +278,6 @@
 42	#	insert into t1 values (1), (2), (3)
 43	#	insert into t1 values (1), (2), (3)
 44	#	select * from t1
-45	#	set session profiling = OFF
 set session profiling = ON;
 select @@profiling;
 @@profiling

--- 1.6/sql/sql_profile.cc	2007-03-28 10:04:41 -04:00
+++ 1.7/sql/sql_profile.cc	2007-03-28 21:21:33 -04:00
@@ -493,6 +493,9 @@
   while (history.elements > thd->variables.profiling_history_size)
     delete history.pop();
 
+  if (likely(((thd)->options & OPTION_PROFILING) == 0))
+    DBUG_VOID_RETURN;
+
   if (current != NULL)
   {
     if (keeping && 
@@ -519,11 +522,19 @@
   DBUG_VOID_RETURN;
 }
 
+/**
+  Store and clean up the old information and get ready to hold info about this
+  new query.  This is called very often so it must be very lightweight if
+  profiling is not active.
+*/
 void PROFILING::reset()
 {
   DBUG_ENTER("PROFILING::reset");
 
   store();
+
+  if (likely(((thd)->options & OPTION_PROFILING) == 0))
+    DBUG_VOID_RETURN;
 
   if (current != NULL)
     current->reset();