From 09774813a4678b7e89c13fda275e18ae6f62b1c1 Mon Sep 17 00:00:00 2001
From: Stefan Reif <reif@cs.fau.de>
Date: Mon, 4 Dec 2017 11:23:56 +0100
Subject: [PATCH] Allow run-time configuration of core pinning

Use the environment variable "PRRT_CORES" to restrict a PRRT socket to
specific cpu cores.
---
 prrt/util/common.c  |   8 +++
 prrt/util/cpulist.h | 148 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 156 insertions(+)
 create mode 100644 prrt/util/cpulist.h

diff --git a/prrt/util/common.c b/prrt/util/common.c
index 780b2f8f..37b2397e 100644
--- a/prrt/util/common.c
+++ b/prrt/util/common.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include <arpa/inet.h>
 
 #include "common.h"
@@ -28,10 +29,17 @@ void print_gf(const gf *start, const int len) {
     printf("\n");
 }
 
+#include "cpulist.h"
 int pin_thread_to_core(pthread_attr_t *ap, int core)
 {
+    char *cpulist_conf = getenv("PRRT_CORES");
+    if (cpulist_conf) {
+        uint32_t cpulist = cpulist_parse(cpulist_conf);
+        core = cpulist_get_cpu(cpulist, core);
+    }
     cpu_set_t cpuset;
     CPU_ZERO(&cpuset);
     CPU_SET(core, &cpuset);
     return pthread_attr_setaffinity_np(ap, sizeof(cpu_set_t), &cpuset);
 }
+
diff --git a/prrt/util/cpulist.h b/prrt/util/cpulist.h
new file mode 100644
index 00000000..32ee920c
--- /dev/null
+++ b/prrt/util/cpulist.h
@@ -0,0 +1,148 @@
+#ifndef PRRT_CPULIST_H
+#define PRRT_CPULIST_H
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <limits.h>
+
+#define CPULIST_ERR ((uint32_t) 0)
+
+#ifdef __GNUC__
+#  define cpulist__inline inline __attribute__((__always_inline__,__unused__))
+#else
+#  define cpulist__inline inline
+#endif
+
+/**
+ * Add a cpu number to a cpu list
+ *
+ * \param cpulist the cpu list
+ * \param num the cpu number
+ * \returns a new cpu list that contains all cpus from the given cpu list, plus
+ * the new number. If the old cpu list already contains the given cpu number,
+ * it is returned unmodified.
+ */
+static cpulist__inline
+uint32_t cpulist_add_cpu(uint32_t cpulist, unsigned int bit) {
+	if (bit >= 32)
+		return cpulist;
+	uint32_t one = 1;
+	return cpulist | (one << bit);
+}
+
+/**
+ * Check if a cpu number is included in a cpu list
+ *
+ * \param cpulist the cpu list
+ * \param num a cpu number
+ * \returns \c true if the cpu list included the given cpu number, \c false otherwise
+ */
+static cpulist__inline
+bool cpulist_has_cpu(uint32_t cpulist, unsigned int num) {
+	if (num >= 32)
+		return false;
+	uint32_t one = 1;
+	return !!(cpulist & (one << num));
+}
+
+/**
+ *
+ * The purpose of this function is to assign arbitrary cpu numbers to cpu
+ * numbers allowed by the given cpu list. This is a very simple way of work
+ * distribution.
+ *
+ * \param cpulist the cpu list
+ * \param num an arbitrary cpu number that is mapped to a cpu number allowed by the given cpu list
+ * \returns a cpu number that is included in the cpu list, if possible
+ * \returns UINT_MAX if the cpu list is empty
+ */
+static cpulist__inline
+unsigned int cpulist_get_cpu(uint32_t cpulist, unsigned int num) {
+	if (!cpulist)
+		return 0;
+	// TODO: find a better load distribution algorithm
+	unsigned int bit = UINT_MAX;
+	bool has = 0;
+	do {
+		num -= has;
+		bit = (bit + 1) & 31;
+		has = cpulist_has_cpu(cpulist, bit);
+	} while (num || !has);
+	return bit;
+}
+
+/**
+ * Remove all large cpu numbers from a cpu list
+ *
+ * This function removes all large cpu numbers from a cpu list. The given limit
+ * is removed as well. Only cpus lower than num remain in the cpu list.
+ *
+ * The purpose of this function is to limit a cpu list to cpu numbers that are
+ * actually available in the system.
+ *
+ * \param cpulist the cpu list
+ * \param num     the cpu limit
+ * \returns the new cpu list with large numbers removed
+ */
+static cpulist__inline
+uint32_t cpulist_cut(uint32_t cpulist, unsigned int num) {
+	uint32_t one = 1;
+	uint32_t all = (one << num) - 1;
+	return cpulist & all;
+}
+
+/**
+ * Parse a cpu list
+ *
+ * This function takes a string that describes a cpu list in an intuitive
+ * format and converts it to a machine-readable cpu list.
+ *
+ * Example: "1-3,5" ==> [ 1, 2, 3, 5 ]
+ *
+ * Syntax:
+ *  cpulist ::= <range> | <range> ',' <range> # comma-separated list of ranges
+ *  range   ::= <num>   | <num> '-' <num>     # single number or actual range
+ *  num     ::= <digit> | <num> <digit>       # at least one digit
+ *  digit   ::= '0' .. '9'
+ */
+static cpulist__inline
+uint32_t cpulist_parse(const char *str)
+{
+	uint32_t result = 0;
+	char *pos = (char *) str;
+	while (*pos) {
+		char *end;
+		long from = strtol(pos, &end, 10);
+		long to;
+		switch(*end) {
+		case '\0':
+		case ',':
+			to = from;
+			break;
+		case '-':
+			pos = end + 1;
+			to = strtol(pos, &end, 10);
+			break;
+		default:
+			return CPULIST_ERR;
+		}
+		pos = end;
+
+		for (long l = from; l <= to; l++)
+			result = cpulist_add_cpu(result, (int) l);
+
+		switch (*pos) {
+		case '\0':
+			return result;
+		case ',':
+			pos++;
+			break;
+		default:
+			return CPULIST_ERR;
+		}
+	}
+	return result;
+}
+
+#endif /* PRRT_CPULIST_H */
-- 
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