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// Copyright 2016 Google Inc. All rights reserved
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// +build ignore
#include "affinity.h"
#include "flags.h"
#include "log.h"
#ifdef __linux__
#include <random>
#include <sched.h>
#include <sys/types.h>
#include <unistd.h>
void SetAffinityForSingleThread() {
cpu_set_t cs;
CPU_ZERO(&cs);
std::default_random_engine generator(getpid());
std::uniform_int_distribution<int> distribution(0, g_flags.num_cpus - 1);
int cpu = distribution(generator);
// Try to come up with a CPU and one close to it. This should work on most
// hyperthreaded system, but may be less optimal under stranger setups.
// Choosing two completely different CPUs would work here as well, it's just a
// couple percent faster if they're close (and still faster than letting the
// scheduler do whatever it wants).
cpu = cpu - (cpu % 2);
CPU_SET(cpu, &cs);
if (g_flags.num_cpus > 1)
CPU_SET(cpu + 1, &cs);
if (sched_setaffinity(0, sizeof(cs), &cs) < 0)
WARN("sched_setaffinity: %s", strerror(errno));
}
void SetAffinityForMultiThread() {
cpu_set_t cs;
CPU_ZERO(&cs);
for (int i = 0; i < g_flags.num_cpus; i++) {
CPU_SET(i, &cs);
}
if (sched_setaffinity(0, sizeof(cs), &cs) < 0)
WARN("sched_setaffinity: %s", strerror(errno));
}
#else
void SetAffinityForSingleThread() {}
void SetAffinityForMultiThread() {}
#endif
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