[trafficserver] branch 9.2.x updated: Slight performance improvements before calling APIHooks::clear (#9480)

[zw...@apache.org]

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zwoop pushed a commit to branch 9.2.x
in repository https://gitbox.apache.org/repos/asf/trafficserver.git


The following commit(s) were added to refs/heads/9.2.x by this push:
     new 782fbfdd1 Slight performance improvements before calling APIHooks::clear (#9480)
782fbfdd1 is described below

commit 782fbfdd1a0a557c19e09ef0d2972007cd2cba9c
Author: Leif Hedstrom <zw...@apache.org>
AuthorDate: Wed Mar 15 15:48:37 2023 -0600

    Slight performance improvements before calling APIHooks::clear (#9480)
    
    (cherry picked from commit c54a2e2b77151869ff014fbdc4c82cec0afcbb8c)
---
 proxy/InkAPIInternal.h | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/proxy/InkAPIInternal.h b/proxy/InkAPIInternal.h
index d140996af..9cad0eb0f 100644
--- a/proxy/InkAPIInternal.h
+++ b/proxy/InkAPIInternal.h
@@ -197,14 +197,24 @@ template <typename ID, int N> FeatureAPIHooks<ID, N>::~FeatureAPIHooks()
   this->clear();
 }
 
+// The APIHooks::clear() method can't be inlined (easily), and we end up calling
+// clear() very frequently (it's used in a number of features). A rough estimate
+// is that we may call APIHooks::clear() as much as 230x per transaction (there's
+// 180 additional APIHooks that should be eliminated in a different PR). This
+// code at least avoids calling this function for a majority of the cases.
+// Before this code, APIHooks::clear() would show up as top 5 in perf top.
 template <typename ID, int N>
 void
 FeatureAPIHooks<ID, N>::clear()
 {
-  for (auto &h : m_hooks) {
-    h.clear();
+  if (m_hooks_p) {
+    for (auto &h : m_hooks) {
+      if (!h.is_empty()) {
+        h.clear();
+      }
+    }
+    m_hooks_p = false;
   }
-  m_hooks_p = false;
 }
 
 template <typename ID, int N>