From 6f15ce125cfe0c8a6ebe8d56b7fcb30d9169e7cf Mon Sep 17 00:00:00 2001
From: John Sully <john@csquare.ca>
Date: Sat, 4 Apr 2020 22:58:17 -0400
Subject: [PATCH] Add the ability to set a starting core # when setting thread
 affinity

Former-commit-id: 9e2e2067c6df5919f1c6b8b9e6e3457c7edc0755
---
 src/config.cpp     | 10 ++++++++--
 src/networking.cpp |  2 +-
 src/server.cpp     |  5 +++--
 src/server.h       |  1 +
 4 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/config.cpp b/src/config.cpp
index 4035ca376..70448a916 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -782,8 +782,14 @@ void loadServerConfigFromString(char *config) {
             } else if (strcasecmp(argv[1], "false") == 0) {
                 cserver.fThreadAffinity = FALSE;
             } else {
-                err = "Unknown argument: server-thread-affinity expects either true or false";
-                goto loaderr;
+                int offset = atoi(argv[1]);
+                if (offset > 0) {
+                    cserver.fThreadAffinity = TRUE;
+                    cserver.threadAffinityOffset = offset-1;
+                } else {
+                    err = "Unknown argument: server-thread-affinity expects either true or false";
+                    goto loaderr;
+                }
             }
         } else if (!strcasecmp(argv[0], "active-replica") && argc == 2) {
             g_pserver->fActiveReplica = yesnotoi(argv[1]);
diff --git a/src/networking.cpp b/src/networking.cpp
index 276095715..fb7d286c6 100644
--- a/src/networking.cpp
+++ b/src/networking.cpp
@@ -1073,7 +1073,7 @@ static void acceptCommonHandler(int fd, int flags, char *ip, int iel) {
     // Set thread affinity
     if (cserver.fThreadAffinity)
     {
-        int cpu = iel;
+        int cpu = iel + cserver.threadAffinityOffset;
         if (setsockopt(fd, SOL_SOCKET, SO_INCOMING_CPU, &cpu, sizeof(iel)) != 0)
         {
             serverLog(LL_WARNING, "Failed to set socket affinity");
diff --git a/src/server.cpp b/src/server.cpp
index 4efe103ab..0c4b3116c 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -2547,6 +2547,7 @@ void initServerConfig(void) {
     /* Multithreading */
     cserver.cthreads = CONFIG_DEFAULT_THREADS;
     cserver.fThreadAffinity = CONFIG_DEFAULT_THREAD_AFFINITY;
+    cserver.threadAffinityOffset = 0;
 }
 
 extern char **environ;
@@ -5350,10 +5351,10 @@ int main(int argc, char **argv) {
 #ifdef __linux__
             cpu_set_t cpuset;
             CPU_ZERO(&cpuset);
-            CPU_SET(iel, &cpuset);
+            CPU_SET(iel + cserver.threadAffinityOffset, &cpuset);
             if (pthread_setaffinity_np(rgthread[iel], sizeof(cpu_set_t), &cpuset) == 0)
             {
-                serverLog(LOG_INFO, "Binding thread %d to cpu %d", iel, iel);
+                serverLog(LOG_INFO, "Binding thread %d to cpu %d", iel, iel + cserver.threadAffinityOffset + 1);
             }
 #else
 			serverLog(LL_WARNING, "CPU pinning not available on this platform");
diff --git a/src/server.h b/src/server.h
index 307321bab..5d5f4b3e0 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1574,6 +1574,7 @@ struct redisServerConst {
 
     int cthreads;               /* Number of main worker threads */
     int fThreadAffinity;        /* Should we pin threads to cores? */
+    int threadAffinityOffset = 0; /* Where should we start pinning them? */
     char *pidfile;              /* PID file path */
 
     /* Fast pointers to often looked up command */