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- // Copyright 2021 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "services/device/compute_pressure/procfs_stat_cpu_parser.h"
- #include <stdint.h>
- #include <limits>
- #include <utility>
- #include <vector>
- #include "base/files/file_path.h"
- #include "base/files/file_util.h"
- #include "base/sequence_checker.h"
- #include "base/strings/string_number_conversions.h"
- #include "base/strings/string_piece.h"
- #include "base/strings/string_split.h"
- #include "base/system/sys_info.h"
- namespace device {
- constexpr base::FilePath::CharType ProcfsStatCpuParser::kProcfsStatPath[];
- ProcfsStatCpuParser::ProcfsStatCpuParser(base::FilePath stat_path)
- : stat_path_(std::move(stat_path)) {
- core_times_.reserve(base::SysInfo::NumberOfProcessors());
- DETACH_FROM_SEQUENCE(sequence_checker_);
- }
- ProcfsStatCpuParser::~ProcfsStatCpuParser() {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- }
- bool ProcfsStatCpuParser::Update() {
- DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
- // This implementation takes advantage of the fact that /proc/stat has 8
- // lines in addition to the per-core lines (cpu0...cpuN). These 8 lines are
- // cpu, intr, ctxt, btime, processes, procs_running, procs_blocked, softirq.
- // Each of these lines consists of a small number of tokens. Each
- // token has a small upper-bound on its size, because tokens are 64-bit
- // base-10 numbers.
- //
- // This has the following consequences.
- // 1) Reading the whole file in memory has a constant size/memory overhead,
- // relative to the class' usage of per-core CoreTime structs.
- // 2) Splitting the entire file into lines and processing each line has a
- // constant size/memory overhead compared to a streaming parser that
- // ignores irrelevant data and stops after the last per-core line (cpuN).
- std::string stat_bytes;
- // This implementation could use base::ReadFileToStringWithMaxSize() to avoid
- // the risk that a kernel bug leads to an OOM. The size limit depends on the
- // maximum number of cores we'd want to support.
- //
- // Each CPU line has ~220 bytes, and the other lines should amount to less
- // than 10,000 bytes. So, for example, a limit of 2.3Mb should be sufficient
- // to support systems up to 10,000 cores.
- if (!base::ReadFileToString(stat_path_, &stat_bytes))
- return false;
- static constexpr base::StringPiece kNewlineSeparator("\n", 1);
- std::vector<base::StringPiece> stat_lines = base::SplitStringPiece(
- stat_bytes, kNewlineSeparator, base::WhitespaceHandling::KEEP_WHITESPACE,
- base::SplitResult::SPLIT_WANT_ALL);
- for (base::StringPiece stat_line : stat_lines) {
- int core_id = CoreIdFromLine(stat_line);
- if (core_id < 0)
- continue;
- DCHECK_LE(core_times_.size(), size_t{std::numeric_limits<int>::max()});
- if (static_cast<int>(core_times_.size()) <= core_id)
- core_times_.resize(core_id + 1);
- CoreTimes& current_core_times = core_times_[core_id];
- UpdateCore(stat_line, current_core_times);
- }
- return true;
- }
- // static
- int ProcfsStatCpuParser::CoreIdFromLine(base::StringPiece stat_line) {
- // The first token of valid lines is cpu<number>. The token is at least 4
- // characters ("cpu" plus one digit).
- auto space_index = stat_line.find(' ');
- if (space_index < 4 || space_index == base::StringPiece::npos)
- return -1;
- if (stat_line[0] != 'c' || stat_line[1] != 'p' || stat_line[2] != 'u')
- return -1;
- base::StringPiece core_id_string = stat_line.substr(3, space_index - 3);
- int core_id;
- if (!base::StringToInt(core_id_string, &core_id) || core_id < 0)
- return -1;
- return core_id;
- }
- // static
- void ProcfsStatCpuParser::UpdateCore(base::StringPiece core_line,
- CoreTimes& core_times) {
- DCHECK_GE(CoreIdFromLine(core_line), 0);
- static constexpr base::StringPiece kSpaceSeparator(" ", 1);
- std::vector<base::StringPiece> tokens = base::SplitStringPiece(
- core_line, kSpaceSeparator, base::WhitespaceHandling::KEEP_WHITESPACE,
- base::SplitResult::SPLIT_WANT_ALL);
- // Accept lines with more than 10 numbers, so the code keeps working if
- // /proc/stat is extended with new per-core metrics.
- //
- // The first token on the line is the "cpuN" core ID. One core ID plus 10
- // numbers equals 11 tokens.
- if (tokens.size() < 11)
- return;
- std::vector<uint64_t> parsed_numbers(10, 0);
- for (int i = 0; i < 10; ++i) {
- uint64_t parsed_number;
- if (!base::StringToUint64(tokens[i + 1], &parsed_number))
- break;
- parsed_numbers[i] = parsed_number;
- }
- core_times.set_user(parsed_numbers[0]);
- core_times.set_nice(parsed_numbers[1]);
- core_times.set_system(parsed_numbers[2]);
- core_times.set_idle(parsed_numbers[3]);
- core_times.set_iowait(parsed_numbers[4]);
- core_times.set_irq(parsed_numbers[5]);
- core_times.set_softirq(parsed_numbers[6]);
- core_times.set_steal(parsed_numbers[7]);
- core_times.set_guest(parsed_numbers[8]);
- core_times.set_guest_nice(parsed_numbers[9]);
- }
- } // namespace device
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