From: Willy Tarreau <w@1wt.eu>
Date: Tue, 11 Jul 2023 16:24:20 +0000 (+0200)
Subject: MINOR: cpu-topo: add detection of online CPUs on Linux
X-Git-Tag: v3.2-dev8~85
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8f72ce335a2b000e621fec0e22bd3b55d88d6069;p=thirdparty%2Fhaproxy.git

MINOR: cpu-topo: add detection of online CPUs on Linux

This adds a generic function ha_cpuset_detect_online() which for now
only supports linux via /sys. It fills a cpuset with the list of online
CPUs that were detected (or returns a failure).
---

diff --git a/include/haproxy/cpu_topo.h b/include/haproxy/cpu_topo.h
index bf7d98f71..74a7e70d2 100644
--- a/include/haproxy/cpu_topo.h
+++ b/include/haproxy/cpu_topo.h
@@ -9,6 +9,12 @@ extern int cpu_topo_maxcpus;
 extern int cpu_topo_lastcpu;
 extern struct ha_cpu_topo *ha_cpu_topo;
 
+/* Detects CPUs that are online on the system. It may rely on FS access (e.g.
+ * /sys on Linux). Returns the number of CPUs detected or 0 if the detection
+ * failed.
+ */
+int ha_cpuset_detect_online(struct hap_cpuset *set);
+
 /* Detects the CPUs that will be used based on the ones the process is bound to.
  * Returns non-zero on success, zero on failure. Note that it may not be
  * performed in the function above because some calls may rely on other items
diff --git a/src/cpu_topo.c b/src/cpu_topo.c
index 1f3495683..ddf45e6ff 100644
--- a/src/cpu_topo.c
+++ b/src/cpu_topo.c
@@ -7,6 +7,8 @@
 #include <haproxy/api.h>
 #include <haproxy/cpuset.h>
 #include <haproxy/cpu_topo.h>
+#include <haproxy/global.h>
+#include <haproxy/tools.h>
 
 /* CPU topology information, ha_cpuset_size() entries, allocated at boot */
 int cpu_topo_maxcpus  = -1;  // max number of CPUs supported by OS/haproxy
@@ -14,6 +16,33 @@ int cpu_topo_lastcpu  = -1;  // last supposed online CPU (no need to look beyond
 struct ha_cpu_topo *ha_cpu_topo = NULL;
 struct cpu_map *cpu_map;
 
+
+/* Detects CPUs that are online on the system. It may rely on FS access (e.g.
+ * /sys on Linux). Returns the number of CPUs detected or 0 if the detection
+ * failed.
+ */
+int ha_cpuset_detect_online(struct hap_cpuset *set)
+{
+#if defined(__linux__)
+
+	ha_cpuset_zero(set);
+
+	/* contains a list of CPUs in the format <low>[-<high>][,...] */
+	if (read_line_to_trash("%s/cpu/online", NUMA_DETECT_SYSTEM_SYSFS_PATH) >= 0) {
+		const char *parse_cpu_set_args[2] = { trash.area, "\0" };
+
+		if (parse_cpu_set(parse_cpu_set_args, set, NULL) != 0)
+			ha_cpuset_zero(set);
+	}
+
+#else // !__linux__
+
+	ha_cpuset_zero(set);
+
+#endif
+	return ha_cpuset_count(set);
+}
+
 /* Detects the CPUs that will be used based on the ones the process is bound to
  * at boot. The principle is the following: all CPUs from the boot cpuset will
  * be used since we don't know upfront how individual threads will be mapped to