51 lines
1.5 KiB
Plaintext
51 lines
1.5 KiB
Plaintext
// Copyright 2023 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "base/system/sys_info.h"
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#include <sys/sysctl.h>
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#include "base/strings/stringprintf.h"
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#include "base/system/sys_info_internal.h"
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namespace base {
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namespace internal {
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// Queries sysctlbyname() for the given key and returns the 32 bit integer value
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// from the system or absl::nullopt on failure.
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// https://github.com/apple/darwin-xnu/blob/2ff845c2e033bd0ff64b5b6aa6063a1f8f65aa32/bsd/sys/sysctl.h#L1224-L1225
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absl::optional<int> GetSysctlIntValue(const char* key_name) {
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int value;
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size_t len = sizeof(value);
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if (sysctlbyname(key_name, &value, &len, nullptr, 0) != 0) {
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return absl::nullopt;
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}
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DCHECK_EQ(len, sizeof(value));
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return value;
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}
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} // namespace internal
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// static
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int SysInfo::NumberOfEfficientProcessorsImpl() {
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int num_perf_levels =
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internal::GetSysctlIntValue("hw.nperflevels").value_or(1);
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if (num_perf_levels == 1) {
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return 0;
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}
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DCHECK_GE(num_perf_levels, 2);
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// Lower values of perflevel indicate higher-performance core types. See
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// https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_system_capabilities?changes=l__5
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int num_of_efficient_processors =
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internal::GetSysctlIntValue(
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StringPrintf("hw.perflevel%d.logicalcpu", num_perf_levels - 1)
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.c_str())
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.value_or(0);
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DCHECK_GE(num_of_efficient_processors, 0);
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return num_of_efficient_processors;
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}
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} // namespace base |