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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
freebsd/current/master
mjg 6 months ago
parent
commit
9a37bec334
1 changed files with 11 additions and 7 deletions
  1. +11
    -7
      sys/tools/vnode_if.awk

+ 11
- 7
sys/tools/vnode_if.awk View File

@@ -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");

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