From be15ec48d7669902f7f7ca2f76fda190b0ccfa5a Mon Sep 17 00:00:00 2001 From: David Marchand Date: Thu, 9 Jun 2016 11:52:49 +0200 Subject: [PATCH] lib: Use a more accurate value for CPU count (sched_getaffinity). Relying on /proc/cpuinfo to count the number of available cores is not the best option: - The code is x86-specific. - If the process is started with a different CPU affinity, then it will wrongly try to start too many threads (for an example, imagine an OVS daemon restricted to 4 CPU threads on a 128 threads system). This commit removes /proc/cpuinfo parsing. For Linux systems, it introduces instead a call to sched_getaffinity(), which is architecture-independant, in order to retrieve the list of CPU threads available to the current process and to count them. Other UNIX-like systems only use _SC_NPROCESSORS_ONLN. Signed-off-by: David Marchand Co-authored-by: Liu Xiaofeng Signed-off-by: Liu Xiaofeng Co-authored-by: Quentin Monnet Signed-off-by: Quentin Monnet Signed-off-by: Ben Pfaff --- lib/ovs-thread.c | 78 ++++++++++-------------------------------------- 1 file changed, 15 insertions(+), 63 deletions(-) diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c index 6e6345273..eee8d9e45 100644 --- a/lib/ovs-thread.c +++ b/lib/ovs-thread.c @@ -547,67 +547,8 @@ ovs_thread_stats_next_bucket(const struct ovsthread_stats *stats, size_t i) } -/* Parses /proc/cpuinfo for the total number of physical cores on this system - * across all CPU packages, not counting hyper-threads. - * - * Sets *n_cores to the total number of cores on this system, or 0 if the +/* Returns the total number of cores available to this process, or 0 if the * number cannot be determined. */ -static void -parse_cpuinfo(long int *n_cores) -{ - static const char file_name[] = "/proc/cpuinfo"; - char line[128]; - uint64_t cpu = 0; /* Support up to 64 CPU packages on a single system. */ - long int cores = 0; - FILE *stream; - - stream = fopen(file_name, "r"); - if (!stream) { - VLOG_DBG("%s: open failed (%s)", file_name, ovs_strerror(errno)); - return; - } - - while (fgets(line, sizeof line, stream)) { - unsigned int id; - - /* Find the next CPU package. */ - if (ovs_scan(line, "physical id%*[^:]: %u", &id)) { - if (id > 63) { - VLOG_WARN("Counted over 64 CPU packages on this system. " - "Parsing %s for core count may be inaccurate.", - file_name); - cores = 0; - break; - } - - if (cpu & (1ULL << id)) { - /* We've already counted this package's cores. */ - continue; - } - cpu |= 1ULL << id; - - /* Find the number of cores for this package. */ - while (fgets(line, sizeof line, stream)) { - int count; - - if (ovs_scan(line, "cpu cores%*[^:]: %u", &count)) { - cores += count; - break; - } - } - } - } - fclose(stream); - - *n_cores = cores; -} - -/* Returns the total number of cores on this system, or 0 if the number cannot - * be determined. - * - * Tries not to count hyper-threads, but may be inaccurate - particularly on - * platforms that do not provide /proc/cpuinfo, but also if /proc/cpuinfo is - * formatted different to the layout that parse_cpuinfo() expects. */ int count_cpu_cores(void) { @@ -616,10 +557,21 @@ count_cpu_cores(void) if (ovsthread_once_start(&once)) { #ifndef _WIN32 - parse_cpuinfo(&n_cores); - if (!n_cores) { - n_cores = sysconf(_SC_NPROCESSORS_ONLN); + n_cores = sysconf(_SC_NPROCESSORS_ONLN); +#ifdef __linux__ + if (n_cores > 0) { + cpu_set_t *set = CPU_ALLOC(n_cores); + + if (set) { + size_t size = CPU_ALLOC_SIZE(n_cores); + + if (!sched_getaffinity(0, size, set)) { + n_cores = CPU_COUNT_S(size, set); + } + CPU_FREE(set); + } } +#endif #else SYSTEM_INFO sysinfo; GetSystemInfo(&sysinfo); -- 2.39.5