From 7b69183a8d556f6a624b97c93b59e69e55fb9934 Mon Sep 17 00:00:00 2001
From: "Filipe Oliveira (Redis)" <filipe@redis.com>
Date: Sun, 15 Sep 2024 14:40:09 +0100
Subject: [PATCH] Replace usage of _addReplyLongLongWithPrefix with specific
 bulk/mbulk functions to reduce condition checks in hotpath. (#13520)

Instead of adding runtime logic to decide which prefix/shared object to
use when doing the reply we can simply use an inline method to avoid runtime
overhead of condition checks, and also keep the code change small.
Preliminary data show improvements on commands that heavily rely on
bulk/mbulk replies (example of LRANGE).

---------

Co-authored-by: debing.sun <debing.sun@redis.com>
---
 src/networking.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/networking.c b/src/networking.c
index 33a8f7b27..47312b8d8 100644
--- a/src/networking.c
+++ b/src/networking.c
@@ -931,6 +931,33 @@ void addReplyHumanLongDouble(client *c, long double d) {
     }
 }
 
+static inline void _addReplyLongLongSharedHdr(client *c, long long ll, char prefix,
+                                              robj *shared_hdr[OBJ_SHARED_BULKHDR_LEN])
+{
+    char buf[128];
+    int len;
+    const int opt_hdr = ll < OBJ_SHARED_BULKHDR_LEN && ll >= 0;
+
+    if (opt_hdr) {
+        _addReplyToBufferOrList(c, shared_hdr[ll]->ptr, OBJ_SHARED_HDR_STRLEN(ll));
+        return;
+    }
+
+    buf[0] = prefix;
+    len = ll2string(buf + 1, sizeof(buf) - 1, ll);
+    buf[len + 1] = '\r';
+    buf[len + 2] = '\n';
+    _addReplyToBufferOrList(c, buf, len + 3);
+}
+
+static inline void _addReplyLongLongBulk(client *c, long long ll) {
+    _addReplyLongLongSharedHdr(c, ll, '$', shared.bulkhdr);
+}
+
+static inline void _addReplyLongLongMBulk(client *c, long long ll) {
+    _addReplyLongLongSharedHdr(c, ll, '*', shared.mbulkhdr);
+}
+
 /* Add a long long as integer reply or bulk len / multi bulk count.
  * Basically this is used to output <prefix><long long><crlf>. */
 static void _addReplyLongLongWithPrefix(client *c, long long ll, char prefix) {
@@ -987,7 +1014,9 @@ void addReplyAggregateLen(client *c, long length, int prefix) {
 }
 
 void addReplyArrayLen(client *c, long length) {
-    addReplyAggregateLen(c,length,'*');
+    serverAssert(length >= 0);
+    if (prepareClientToWrite(c) != C_OK) return;
+    _addReplyLongLongMBulk(c, length);
 }
 
 void addReplyMapLen(client *c, long length) {
@@ -1044,7 +1073,7 @@ void addReplyNullArray(client *c) {
 void addReplyBulkLen(client *c, robj *obj) {
     size_t len = stringObjectLen(obj);
     if (prepareClientToWrite(c) != C_OK) return;
-    _addReplyLongLongWithPrefix(c, len, '$');
+    _addReplyLongLongBulk(c, len);
 }
 
 /* Add a Redis Object as a bulk reply */
@@ -1057,7 +1086,7 @@ void addReplyBulk(client *c, robj *obj) {
 /* Add a C buffer as bulk reply */
 void addReplyBulkCBuffer(client *c, const void *p, size_t len) {
     if (prepareClientToWrite(c) != C_OK) return;
-    _addReplyLongLongWithPrefix(c, len, '$');
+    _addReplyLongLongBulk(c, len);
     _addReplyToBufferOrList(c, p, len);
     _addReplyToBufferOrList(c, "\r\n", 2);
 }