Optimize performance schema likely/unlikely

Performance schema likely/unlikely assume that performance schema
is enabled by default, which causes a performance degradation for
default installations that doesn't have performance schema enabled.

Fixed by changing the likely/unlikely in PS to assume it's
not enabled. This can be changed by compiling with
-DPSI_ON_BY_DEFAULT

Other changes:
- Added psi_likely/psi_unlikely that is depending on
  PSI_ON_BY_DEFAULT. psi_likely() is assumed to be true
  if PS is enabled.
- Added likely/unlikely to some PS interface code.
- Moved pfs_enabled to mysys (was initialized but not used before)
- Added "if (pfs_likely(pfs_enabled))" around calls to PS to avoid
  an extra call if PS is not enabled.
- Moved checking flag_global_instrumention before other flags
  to speed up the case when PS is not enabled.

3 files changed, 10 insertions, 3 deletions

diff --git a/mysys/file_logger.c b/mysys/file_logger.c
index 35a077c4391..3565397c79a 100644
--- a/mysys/file_logger.c
+++ b/mysys/file_logger.c
@@ -227,7 +227,7 @@ int logger_printf(LOGGER_HANDLE *log, const char *fmt, ...)
 void logger_init_mutexes()
 {
 #ifdef HAVE_PSI_INTERFACE
-  if (PSI_server)
+  if (unlikely(PSI_server))
     PSI_server->register_mutex("sql_logger", mutex_list, 1);
 #endif
 }
diff --git a/mysys/my_likely.c b/mysys/my_likely.c
index 9b32c65d6a0..c6fca5b7146 100644
--- a/mysys/my_likely.c
+++ b/mysys/my_likely.c
@@ -121,14 +121,14 @@ static LIKELY_ENTRY *my_likely_find(const char *file_name, uint line)
 {
   char key[80], *pos;
   LIKELY_ENTRY *entry;
-  uint length;
+  size_t length;
 
   if (!likely_inited)
     return 0;
 
   pos= strnmov(key, file_name, sizeof(key)-4);
   int3store(pos+1, line);
-  length= (pos-key)+4;
+  length= (size_t) (pos-key)+4;
 
   pthread_mutex_lock(&likely_mutex);
   if (!(entry= (LIKELY_ENTRY*) my_hash_search(&likely_hash, (uchar*) key,
diff --git a/mysys/psi_noop.c b/mysys/psi_noop.c
index 6eecf56f797..f8fa2c92f63 100644
--- a/mysys/psi_noop.c
+++ b/mysys/psi_noop.c
@@ -763,6 +763,13 @@ struct PSI_bootstrap *PSI_hook= NULL;
 
 PSI *PSI_server= & PSI_noop;
 
+/**
+  Global performance schema flag.
+  Indicate if the performance schema is enabled.
+  This flag is set at startup, and never changes.
+*/
+my_bool pfs_enabled= FALSE;
+
 void set_psi_server(PSI *psi)
 {
   PSI_server= psi;