Reduce redundant call of prepareClientToWrite when call addReply* con…

…tinuously (redis#13412)

This PR is based on the commits from PR
valkey-io/valkey#670.

## Description

While exploring hotspots with profiling some benchmark workloads, we
noticed the high cycles ratio of `prepareClientToWrite`, taking about 9%
of the CPU of `smembers`, `lrange` commands. After deep dive the code
logic, we thought we can gain the performance by reducing the redundant
call of `prepareClientToWrite` when call addReply* continuously.

For example: In

https://github.com/valkey-io/valkey/blob/unstable/src/networking.c#L1080-L1082,
`prepareClientToWrite` is called three times in a row.

---------

Signed-off-by: Lipeng Zhu <lipeng.zhu@intel.com>
Co-authored-by: Lipeng Zhu <lipeng.zhu@intel.com>
Co-authored-by: Wangyang Guo <wangyang.guo@intel.com>

src/networking.c

@@ -2,8 +2,13 @@
  * Copyright (c) 2009-Present, Redis Ltd.
  * All rights reserved.
  *
+ * Copyright (c) 2024-present, Valkey contributors.
+ * All rights reserved.
+ *
  * Licensed under your choice of the Redis Source Available License 2.0
  * (RSALv2) or the Server Side Public License v1 (SSPLv1).
+ *
+ * Portions of this file are available under BSD3 terms; see REDISCONTRIBUTIONS for more information.
  */
 
 #include "server.h"
@@ -924,7 +929,7 @@ void addReplyHumanLongDouble(client *c, long double d) {
 
 /* Add a long long as integer reply or bulk len / multi bulk count.
  * Basically this is used to output <prefix><long long><crlf>. */
-void addReplyLongLongWithPrefix(client *c, long long ll, char prefix) {
+static void _addReplyLongLongWithPrefix(client *c, long long ll, char prefix) {
     char buf[128];
     int len;
 
@@ -934,38 +939,41 @@ void addReplyLongLongWithPrefix(client *c, long long ll, char prefix) {
     const int opt_hdr = ll < OBJ_SHARED_BULKHDR_LEN && ll >= 0;
     const size_t hdr_len = OBJ_SHARED_HDR_STRLEN(ll);
     if (prefix == '*' && opt_hdr) {
-        addReplyProto(c,shared.mbulkhdr[ll]->ptr,hdr_len);
+        _addReplyToBufferOrList(c, shared.mbulkhdr[ll]->ptr, hdr_len);
         return;
     } else if (prefix == '$' && opt_hdr) {
-        addReplyProto(c,shared.bulkhdr[ll]->ptr,hdr_len);
+        _addReplyToBufferOrList(c, shared.bulkhdr[ll]->ptr, hdr_len);
         return;
     } else if (prefix == '%' && opt_hdr) {
-        addReplyProto(c,shared.maphdr[ll]->ptr,hdr_len);
+        _addReplyToBufferOrList(c, shared.maphdr[ll]->ptr, hdr_len);
         return;
     } else if (prefix == '~' && opt_hdr) {
-        addReplyProto(c,shared.sethdr[ll]->ptr,hdr_len);
+        _addReplyToBufferOrList(c, shared.sethdr[ll]->ptr, hdr_len);
         return;
     }
 
     buf[0] = prefix;
-    len = ll2string(buf+1,sizeof(buf)-1,ll);
-    buf[len+1] = '\r';
-    buf[len+2] = '\n';
-    addReplyProto(c,buf,len+3);
+    len = ll2string(buf + 1, sizeof(buf) - 1, ll);
+    buf[len + 1] = '\r';
+    buf[len + 2] = '\n';
+    _addReplyToBufferOrList(c, buf, len + 3);
 }
 
 void addReplyLongLong(client *c, long long ll) {
     if (ll == 0)
         addReply(c,shared.czero);
     else if (ll == 1)
-        addReply(c,shared.cone);
-    else
-        addReplyLongLongWithPrefix(c,ll,':');
+        addReply(c, shared.cone);
+    else {
+        if (prepareClientToWrite(c) != C_OK) return;
+        _addReplyLongLongWithPrefix(c, ll, ':');
+    }
 }
 
 void addReplyAggregateLen(client *c, long length, int prefix) {
     serverAssert(length >= 0);
-    addReplyLongLongWithPrefix(c,length,prefix);
+    if (prepareClientToWrite(c) != C_OK) return;
+    _addReplyLongLongWithPrefix(c, length, prefix);
 }
 
 void addReplyArrayLen(client *c, long length) {
@@ -1025,8 +1033,8 @@ void addReplyNullArray(client *c) {
 /* Create the length prefix of a bulk reply, example: $2234 */
 void addReplyBulkLen(client *c, robj *obj) {
     size_t len = stringObjectLen(obj);
-
-    addReplyLongLongWithPrefix(c,len,'$');
+    if (prepareClientToWrite(c) != C_OK) return;
+    _addReplyLongLongWithPrefix(c, len, '$');
 }
 
 /* Add a Redis Object as a bulk reply */
@@ -1038,16 +1046,22 @@ void addReplyBulk(client *c, robj *obj) {
 
 /* Add a C buffer as bulk reply */
 void addReplyBulkCBuffer(client *c, const void *p, size_t len) {
-    addReplyLongLongWithPrefix(c,len,'$');
-    addReplyProto(c,p,len);
-    addReplyProto(c,"\r\n",2);
+    if (prepareClientToWrite(c) != C_OK) return;
+    _addReplyLongLongWithPrefix(c, len, '$');
+    _addReplyToBufferOrList(c, p, len);
+    _addReplyToBufferOrList(c, "\r\n", 2);
 }
 
 /* Add sds to reply (takes ownership of sds and frees it) */
-void addReplyBulkSds(client *c, sds s)  {
-    addReplyLongLongWithPrefix(c,sdslen(s),'$');
-    addReplySds(c,s);
-    addReplyProto(c,"\r\n",2);
+void addReplyBulkSds(client *c, sds s) {
+    if (prepareClientToWrite(c) != C_OK) {
+        sdsfree(s);
+        return;
+    }
+    _addReplyLongLongWithPrefix(c, sdslen(s), '$');
+    _addReplyToBufferOrList(c, s, sdslen(s));
+    sdsfree(s);
+    _addReplyToBufferOrList(c, "\r\n", 2);
 }
 
 /* Set sds to a deferred reply (for symmetry with addReplyBulkSds it also frees the sds) */

src/server.h

@@ -2,6 +2,9 @@
  * Copyright (c) 2009-Present, Redis Ltd.
  * All rights reserved.
  *
+ * Copyright (c) 2024-present, Valkey contributors.
+ * All rights reserved.
+ *
  * Licensed under your choice of the Redis Source Available License 2.0
  * (RSALv2) or the Server Side Public License v1 (SSPLv1).
  *
@@ -2620,8 +2623,7 @@ void addReplyErrorArity(client *c);
 void addReplyErrorExpireTime(client *c);
 void addReplyStatus(client *c, const char *status);
 void addReplyDouble(client *c, double d);
-void addReplyLongLongWithPrefix(client *c, long long ll, char prefix);
-void addReplyBigNum(client *c, const char* num, size_t len);
+void addReplyBigNum(client *c, const char *num, size_t len);
 void addReplyHumanLongDouble(client *c, long double d);
 void addReplyLongLong(client *c, long long ll);
 void addReplyArrayLen(client *c, long length);