From 966920e063cc1fa276fbc09798779d71be51947d Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@ionos.com>
Date: Thu, 3 Oct 2024 17:21:23 +0200
Subject: [PATCH] msg/async/ProtocolV2: pass `desc` as `std::string_view` to
 write()

All callers really pass a C string literal, and declaring a
`std::string` parameter will implicitly create two `std::string`
instances: one on the caller's stack, and another one inside write()
as parameter to the continuation lambda.  This causes considerable and
unnecessary overhead.

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 src/msg/async/ProtocolV2.cc | 4 ++--
 src/msg/async/ProtocolV2.h  | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/msg/async/ProtocolV2.cc b/src/msg/async/ProtocolV2.cc
index 6d44d6c783f44..c4cfa76d16f15 100644
--- a/src/msg/async/ProtocolV2.cc
+++ b/src/msg/async/ProtocolV2.cc
@@ -796,7 +796,7 @@ CtPtr ProtocolV2::read(CONTINUATION_RXBPTR_TYPE<ProtocolV2> &next,
 }
 
 template <class F>
-CtPtr ProtocolV2::write(const std::string &desc,
+CtPtr ProtocolV2::write(std::string_view desc,
                         CONTINUATION_TYPE<ProtocolV2> &next,
                         F &frame) {
   ceph::bufferlist bl;
@@ -812,7 +812,7 @@ CtPtr ProtocolV2::write(const std::string &desc,
   return write(desc, next, bl);
 }
 
-CtPtr ProtocolV2::write(const std::string &desc,
+CtPtr ProtocolV2::write(std::string_view desc,
                         CONTINUATION_TYPE<ProtocolV2> &next,
                         ceph::bufferlist &buffer) {
   if (unlikely(pre_auth.enabled)) {
diff --git a/src/msg/async/ProtocolV2.h b/src/msg/async/ProtocolV2.h
index 6441866fea4c3..918003a21ced7 100644
--- a/src/msg/async/ProtocolV2.h
+++ b/src/msg/async/ProtocolV2.h
@@ -130,10 +130,10 @@ class ProtocolV2 : public Protocol {
   Ct<ProtocolV2> *read(CONTINUATION_RXBPTR_TYPE<ProtocolV2> &next,
                        rx_buffer_t&& buffer);
   template <class F>
-  Ct<ProtocolV2> *write(const std::string &desc,
+  Ct<ProtocolV2> *write(std::string_view desc,
                         CONTINUATION_TYPE<ProtocolV2> &next,
 			F &frame);
-  Ct<ProtocolV2> *write(const std::string &desc,
+  Ct<ProtocolV2> *write(std::string_view desc,
                         CONTINUATION_TYPE<ProtocolV2> &next,
                         ceph::bufferlist &buffer);