From a2012b80b1e045c94e6c93a2f959df75d9ce1fa3 Mon Sep 17 00:00:00 2001
From: Donald Sharp <sharpd@cumulusnetworks.com>
Date: Thu, 10 Nov 2016 13:58:40 -0500
Subject: [PATCH] lib: Slight Optimization of thread handling.

This commit does these things:

1) Make thread_add_unuse own the setting of THREAD_UNUSED.
2) Move thread->hist finding to to thread_get.
   We are storing the thread->hist even when the thread
   is on the unused.  This means that we check to see
   if the funcname or func have changed and we get new
   history.  Else we've probably just retrieved the last
   unused which has the same func/funcanme.  This is
   a common practice to do THREAD_OFF/THREAD_ON in
   quick succession.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com.
---
 lib/thread.c | 45 ++++++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/lib/thread.c b/lib/thread.c
index eac7f3250b..59c0b77b90 100644
--- a/lib/thread.c
+++ b/lib/thread.c
@@ -570,7 +570,8 @@ thread_add_unuse (struct thread_master *m, struct thread *thread)
   assert (m != NULL && thread != NULL);
   assert (thread->next == NULL);
   assert (thread->prev == NULL);
-  assert (thread->type == THREAD_UNUSED);
+
+  thread->type = THREAD_UNUSED;
   thread_list_add (&m->unuse, thread);
 }
 
@@ -693,6 +694,7 @@ thread_get (struct thread_master *m, u_char type,
 	    int (*func) (struct thread *), void *arg, debugargdef)
 {
   struct thread *thread = thread_trim_head (&m->unuse);
+  struct cpu_thread_history tmp;
 
   if (! thread)
     {
@@ -702,11 +704,29 @@ thread_get (struct thread_master *m, u_char type,
   thread->type = type;
   thread->add_type = type;
   thread->master = m;
-  thread->func = func;
   thread->arg = arg;
   thread->index = -1;
   thread->yield = THREAD_YIELD_TIME_SLOT; /* default */
 
+  /*
+   * So if the passed in funcname is not what we have
+   * stored that means the thread->hist needs to be
+   * updated.  We keep the last one around in unused
+   * under the assumption that we are probably
+   * going to immediately allocate the same
+   * type of thread.
+   * This hopefully saves us some serious
+   * hash_get lookups.
+   */
+  if (thread->funcname != funcname ||
+      thread->func != func)
+    {
+      tmp.func = func;
+      tmp.funcname = funcname;
+      thread->hist = hash_get (cpu_record, &tmp,
+			       (void * (*) (void *))cpu_record_hash_alloc);
+    }
+  thread->func = func;
   thread->funcname = funcname;
   thread->schedfrom = schedfrom;
   thread->schedfrom_line = fromln;
@@ -1063,7 +1083,6 @@ thread_cancel (struct thread *thread)
       assert(!"Thread should be either in queue or list or array!");
     }
 
-  thread->type = THREAD_UNUSED;
   thread_add_unuse (thread->master, thread);
 }
 
@@ -1086,7 +1105,6 @@ thread_cancel_event (struct thread_master *m, void *arg)
         {
           ret++;
           thread_list_delete (&m->event, t);
-          t->type = THREAD_UNUSED;
           thread_add_unuse (m, t);
         }
     }
@@ -1104,7 +1122,6 @@ thread_cancel_event (struct thread_master *m, void *arg)
         {
           ret++;
           thread_list_delete (&m->ready, t);
-          t->type = THREAD_UNUSED;
           thread_add_unuse (m, t);
         }
     }
@@ -1128,7 +1145,6 @@ thread_run (struct thread_master *m, struct thread *thread,
 	    struct thread *fetch)
 {
   *fetch = *thread;
-  thread->type = THREAD_UNUSED;
   thread_add_unuse (m, thread);
   return fetch;
 }
@@ -1427,23 +1443,6 @@ thread_call (struct thread *thread)
   unsigned long realtime, cputime;
   RUSAGE_T before, after;
 
- /* Cache a pointer to the relevant cpu history thread, if the thread
-  * does not have it yet.
-  *
-  * Callers submitting 'dummy threads' hence must take care that
-  * thread->cpu is NULL
-  */
-  if (!thread->hist)
-    {
-      struct cpu_thread_history tmp;
-      
-      tmp.func = thread->func;
-      tmp.funcname = thread->funcname;
-      
-      thread->hist = hash_get (cpu_record, &tmp, 
-                    (void * (*) (void *))cpu_record_hash_alloc);
-    }
-
   GETRUSAGE (&before);
   thread->real = before.real;
 
-- 
2.39.5