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From: Martin Liska <marxin@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-49] Revert "Use std::thread::hardware_concurrency in lto-wrapper.c." Date: Wed, 21 Apr 2021 19:34:16 +0000 (GMT) [thread overview] Message-ID: <20210421193416.36E933857817@sourceware.org> (raw) https://gcc.gnu.org/g:f2b4f212a97ae137c2a8ecafe7ed2cb5b5016b6b commit r12-49-gf2b4f212a97ae137c2a8ecafe7ed2cb5b5016b6b Author: Martin Liska <mliska@suse.cz> Date: Wed Apr 21 21:33:41 2021 +0200 Revert "Use std::thread::hardware_concurrency in lto-wrapper.c." This reverts commit 0a18305ee11e139838771f96c5a037a29606236e. Diff: --- gcc/lto-wrapper.c | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 108 insertions(+), 5 deletions(-) diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c index 6ba401007f6..0b626d7c811 100644 --- a/gcc/lto-wrapper.c +++ b/gcc/lto-wrapper.c @@ -49,8 +49,6 @@ along with GCC; see the file COPYING3. If not see #include "lto-section-names.h" #include "collect-utils.h" -#include <thread> - /* Environment variable, used for passing the names of offload targets from GCC driver to lto-wrapper. */ #define OFFLOAD_TARGET_NAMES_ENV "OFFLOAD_TARGET_NAMES" @@ -1201,6 +1199,113 @@ cmp_priority (const void *a, const void *b) return *((const int *)b)-*((const int *)a); } +/* Number of CPUs that can be used for parallel LTRANS phase. */ + +static unsigned long nthreads_var = 0; + +#ifdef HAVE_PTHREAD_AFFINITY_NP +unsigned long cpuset_size; +static unsigned long get_cpuset_size; +cpu_set_t *cpusetp; + +unsigned long +static cpuset_popcount (unsigned long cpusetsize, cpu_set_t *cpusetp) +{ +#ifdef CPU_COUNT_S + /* glibc 2.7 and above provide a macro for this. */ + return CPU_COUNT_S (cpusetsize, cpusetp); +#else +#ifdef CPU_COUNT + if (cpusetsize == sizeof (cpu_set_t)) + /* glibc 2.6 and above provide a macro for this. */ + return CPU_COUNT (cpusetp); +#endif + size_t i; + unsigned long ret = 0; + STATIC_ASSERT (sizeof (cpusetp->__bits[0]) == sizeof (unsigned long int)); + for (i = 0; i < cpusetsize / sizeof (cpusetp->__bits[0]); i++) + { + unsigned long int mask = cpusetp->__bits[i]; + if (mask == 0) + continue; + ret += __builtin_popcountl (mask); + } + return ret; +#endif +} +#endif + +/* At startup, determine the default number of threads. It would seem + this should be related to the number of cpus online. */ + +static void +init_num_threads (void) +{ +#ifdef HAVE_PTHREAD_AFFINITY_NP +#if defined (_SC_NPROCESSORS_CONF) && defined (CPU_ALLOC_SIZE) + cpuset_size = sysconf (_SC_NPROCESSORS_CONF); + cpuset_size = CPU_ALLOC_SIZE (cpuset_size); +#else + cpuset_size = sizeof (cpu_set_t); +#endif + + cpusetp = (cpu_set_t *) xmalloc (gomp_cpuset_size); + do + { + int ret = pthread_getaffinity_np (pthread_self (), gomp_cpuset_size, + cpusetp); + if (ret == 0) + { + /* Count only the CPUs this process can use. */ + nthreads_var = cpuset_popcount (cpuset_size, cpusetp); + if (nthreads_var == 0) + break; + get_cpuset_size = cpuset_size; +#ifdef CPU_ALLOC_SIZE + unsigned long i; + for (i = cpuset_size * 8; i; i--) + if (CPU_ISSET_S (i - 1, cpuset_size, cpusetp)) + break; + cpuset_size = CPU_ALLOC_SIZE (i); +#endif + return; + } + if (ret != EINVAL) + break; +#ifdef CPU_ALLOC_SIZE + if (cpuset_size < sizeof (cpu_set_t)) + cpuset_size = sizeof (cpu_set_t); + else + cpuset_size = cpuset_size * 2; + if (cpuset_size < 8 * sizeof (cpu_set_t)) + cpusetp + = (cpu_set_t *) realloc (cpusetp, cpuset_size); + else + { + /* Avoid fatal if too large memory allocation would be + requested, e.g. kernel returning EINVAL all the time. */ + void *p = realloc (cpusetp, cpuset_size); + if (p == NULL) + break; + cpusetp = (cpu_set_t *) p; + } +#else + break; +#endif + } + while (1); + cpuset_size = 0; + nthreads_var = 1; + free (cpusetp); + cpusetp = NULL; +#endif +#ifdef _SC_NPROCESSORS_ONLN + nthreads_var = sysconf (_SC_NPROCESSORS_ONLN); +#endif +} + +/* FIXME: once using -std=c++11, we can use std::thread::hardware_concurrency. */ + /* Test and return reason why a jobserver cannot be detected. */ static const char * @@ -1284,9 +1389,6 @@ run_gcc (unsigned argc, char *argv[]) const char *incoming_dumppfx = dumppfx = NULL; static char current_dir[] = { '.', DIR_SEPARATOR, '\0' }; - /* Number of CPUs that can be used for parallel LTRANS phase. */ - unsigned long nthreads_var = std::thread::hardware_concurrency (); - /* Get the driver and options. */ collect_gcc = getenv ("COLLECT_GCC"); if (!collect_gcc) @@ -1678,6 +1780,7 @@ cont1: else if (auto_parallel) { char buf[256]; + init_num_threads (); if (nthreads_var == 0) nthreads_var = 1; if (verbose)
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