svn commit: r355791 - head/sys/tools

[Mateusz Guzik]

Author: mjg
Date: Mon Dec 16 00:07:51 2019
New Revision: 355791
URL: https://svnweb.freebsd.org/changeset/base/355791

Log:
  vfs: allow tail call optimisation in vops in the common case
  
  Most frequently used vops boil down to checking SDT probes, doing the call and
  checking again. There is no vop_post/pre in their case but the check after the
  call prevents tail call optimisation from taking place. Instead, check once
  upfront. Kernels with debug or vops with non-empty vop_post still don't short
  circuit.
  
  Reviewed by:	kib
  Tested by:	pho
  Differential Revision:	https://reviews.freebsd.org/D22739

Modified:
  head/sys/tools/vnode_if.awk

Modified: head/sys/tools/vnode_if.awk
==============================================================================
--- head/sys/tools/vnode_if.awk	Mon Dec 16 00:06:22 2019	(r355790)
+++ head/sys/tools/vnode_if.awk	Mon Dec 16 00:07:51 2019	(r355791)
@@ -363,16 +363,20 @@ while ((getline < srcfile) > 0) {
 		printc("\tVNASSERT(a->a_gen.a_desc == &" name "_desc, a->a_" args[0]",");
 		printc("\t    (\"Wrong a_desc in " name "(%p, %p)\", a->a_" args[0]", a));");
 		printc("\tVNASSERT(vop != NULL, a->a_" args[0]", (\"No "name"(%p, %p)\", a->a_" args[0]", a));")
-		printc("\tSDT_PROBE2(vfs, vop, " name ", entry, a->a_" args[0] ", a);\n");
-		for (i = 0; i < numargs; ++i)
-			add_debug_code(name, args[i], "Entry", "\t");
 		printc("\tKTR_START" ctrstr);
 		add_pre(name);
-		printc("\tif (vop->"name" != NULL)")
+		for (i = 0; i < numargs; ++i)
+			add_debug_code(name, args[i], "Entry", "\t");
+		printc("\tif (__predict_true(!SDT_PROBES_ENABLED() && vop->"name" != NULL)) {");
 		printc("\t\trc = vop->"name"(a);")
-		printc("\telse")
-		printc("\t\trc = vop->vop_bypass(&a->a_gen);")
-		printc("\tSDT_PROBE3(vfs, vop, " name ", return, a->a_" args[0] ", a, rc);\n");
+		printc("\t} else {")
+		printc("\t\tSDT_PROBE2(vfs, vop, " name ", entry, a->a_" args[0] ", a);");
+		printc("\t\tif (vop->"name" != NULL)")
+		printc("\t\t\trc = vop->"name"(a);")
+		printc("\t\telse")
+		printc("\t\t\trc = vop->vop_bypass(&a->a_gen);")
+		printc("\t\tSDT_PROBE3(vfs, vop, " name ", return, a->a_" args[0] ", a, rc);");
+		printc("\t}")
 		printc("\tif (rc == 0) {");
 		for (i = 0; i < numargs; ++i)
 			add_debug_code(name, args[i], "OK", "\t\t");