diff --git a/include/haproxy/defaults.h b/include/haproxy/defaults.h
index a6337e9c3..35ad50d04 100644
--- a/include/haproxy/defaults.h
+++ b/include/haproxy/defaults.h
@@ -27,16 +27,25 @@
  * but may be lowered to save resources on embedded systems.
 */
 #ifndef USE_THREAD
-/* threads disabled, 1 thread max */
+/* threads disabled, 1 thread max, 1 group max (note: group ids start at 1) */
 #define MAX_THREADS 1
 #define MAX_THREADS_MASK 1
 
+#define MAX_TGROUPS 1
+#define MAX_THREADS_PER_GROUP 1
+
 #else
 /* threads enabled, max_threads defaults to long bits */
 #ifndef MAX_THREADS
 #define MAX_THREADS LONGBITS
 #endif
 #define MAX_THREADS_MASK (~0UL >> (LONGBITS - MAX_THREADS))
+
+/* still limited to 1 group for now by default (note: group ids start at 1) */
+#ifndef MAX_TGROUPS
+#define MAX_TGROUPS 1
+#endif
+#define MAX_THREADS_PER_GROUP LONGBITS
 #endif
 
 /*
diff --git a/include/haproxy/tinfo-t.h b/include/haproxy/tinfo-t.h
index fe9ef9bd0..963d0a937 100644
--- a/include/haproxy/tinfo-t.h
+++ b/include/haproxy/tinfo-t.h
@@ -38,6 +38,20 @@ enum {
 /* thread_ctx flags, for ha_thread_ctx[].flags */
 #define TH_FL_STUCK             0x00000001
 
+/* Thread group information. This defines a base and a count of global thread
+ * IDs which belong to it, and which can be looked up into thread_info/ctx. It
+ * is set up during parsing and is stable during operation. Thread groups start
+ * at 1 so tgroup[0] describes thread group 1.
+ */
+struct tgroup_info {
+	uint base;                 /* first thread in this group */
+	uint count;                /* number of threads in this group */
+
+	/* pad to cache line (64B) */
+	char __pad[0];            /* unused except to check remaining room */
+	char __end[0] __attribute__((aligned(64)));
+};
+
 /* This structure describes all the per-thread info we need. When threads are
  * disabled, it contains the same info for the single running thread. This is
  * stable across all of a thread's life, and is being pointed to by the
diff --git a/include/haproxy/tinfo.h b/include/haproxy/tinfo.h
index a1b73463f..6b654f987 100644
--- a/include/haproxy/tinfo.h
+++ b/include/haproxy/tinfo.h
@@ -26,6 +26,9 @@
 #include <haproxy/tinfo-t.h>
 
 /* the structs are in thread.c */
+extern struct tgroup_info ha_tgroup_info[MAX_TGROUPS];
+extern THREAD_LOCAL const struct tgroup_info *tg;
+
 extern struct thread_info ha_thread_info[MAX_THREADS];
 extern THREAD_LOCAL const struct thread_info *ti;   /* thread_info for the current thread */
 
diff --git a/src/thread.c b/src/thread.c
index 14bf21eba..445a73fa8 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -50,6 +50,9 @@
 #include <haproxy/thread.h>
 #include <haproxy/tools.h>
 
+struct tgroup_info ha_tgroup_info[MAX_TGROUPS] = { };
+THREAD_LOCAL const struct tgroup_info *tg = &ha_tgroup_info[0];
+
 struct thread_info ha_thread_info[MAX_THREADS] = { };
 THREAD_LOCAL const struct thread_info *ti = &ha_thread_info[0];