base/process/process_linux.cc

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/process/process.h"
   6
   7 #include <errno.h>
   8 #include <sys/resource.h>
   9
  10 #include "base/files/file_util.h"
  11 #include "base/lazy_instance.h"
  12 #include "base/logging.h"
  13 #include "base/strings/string_split.h"
  14 #include "base/strings/stringprintf.h"
  15 #include "base/synchronization/lock.h"
  16
  17 namespace base {
  18
  19 namespace {
  20
  21 const int kForegroundPriority = 0;
  22
  23 #if defined(OS_CHROMEOS)
  24 // We are more aggressive in our lowering of background process priority
  25 // for chromeos as we have much more control over other processes running
  26 // on the machine.
  27 //
  28 // TODO(davemoore) Refactor this by adding support for higher levels to set
  29 // the foregrounding / backgrounding process so we don't have to keep
  30 // chrome / chromeos specific logic here.
  31 const int kBackgroundPriority = 19;
  32 const char kControlPath[] = "/sys/fs/cgroup/cpu%s/cgroup.procs";
  33 const char kForeground[] = "/chrome_renderers/foreground";
  34 const char kBackground[] = "/chrome_renderers/background";
  35 const char kProcPath[] = "/proc/%d/cgroup";
  36
  37 struct CGroups {
  38   // Check for cgroups files. ChromeOS supports these by default. It creates
  39   // a cgroup mount in /sys/fs/cgroup and then configures two cpu task groups,
  40   // one contains at most a single foreground renderer and the other contains
  41   // all background renderers. This allows us to limit the impact of background
  42   // renderers on foreground ones to a greater level than simple renicing.
  43   bool enabled;
  44   base::FilePath foreground_file;
  45   base::FilePath background_file;
  46
  47   CGroups() {
  48     foreground_file =
  49         base::FilePath(base::StringPrintf(kControlPath, kForeground));
  50     background_file =
  51         base::FilePath(base::StringPrintf(kControlPath, kBackground));
  52     base::FileSystemType foreground_type;
  53     base::FileSystemType background_type;
  54     enabled =
  55         base::GetFileSystemType(foreground_file, &foreground_type) &&
  56         base::GetFileSystemType(background_file, &background_type) &&
  57         foreground_type == FILE_SYSTEM_CGROUP &&
  58         background_type == FILE_SYSTEM_CGROUP;
  59   }
  60 };
  61
  62 base::LazyInstance<CGroups> cgroups = LAZY_INSTANCE_INITIALIZER;
  63 #else
  64 const int kBackgroundPriority = 5;
  65 #endif
  66
  67 struct CheckForNicePermission {
  68   CheckForNicePermission() : can_reraise_priority(false) {
  69     // We won't be able to raise the priority if we don't have the right rlimit.
  70     // The limit may be adjusted in /etc/security/limits.conf for PAM systems.
  71     struct rlimit rlim;
  72     if ((getrlimit(RLIMIT_NICE, &rlim) == 0) &&
  73         (20 - kForegroundPriority) <= static_cast<int>(rlim.rlim_cur)) {
  74         can_reraise_priority = true;
  75     }
  76   };
  77
  78   bool can_reraise_priority;
  79 };
  80
  81 }  // namespace
  82
  83 // static
  84 bool Process::CanBackgroundProcesses() {
  85 #if defined(OS_CHROMEOS)
  86   if (cgroups.Get().enabled)
  87     return true;
  88 #endif
  89
  90   static LazyInstance<CheckForNicePermission> check_for_nice_permission =
  91       LAZY_INSTANCE_INITIALIZER;
  92   return check_for_nice_permission.Get().can_reraise_priority;
  93 }
  94
  95 bool Process::IsProcessBackgrounded() const {
  96   DCHECK(IsValid());
  97
  98 #if defined(OS_CHROMEOS)
  99   if (cgroups.Get().enabled) {
 100     std::string proc;
 101     if (base::ReadFileToString(
 102             base::FilePath(StringPrintf(kProcPath, process_)),
 103             &proc)) {
 104       std::vector<std::string> proc_parts;
 105       base::SplitString(proc, ':', &proc_parts);
 106       DCHECK_EQ(proc_parts.size(), 3u);
 107       bool ret = proc_parts[2] == std::string(kBackground);
 108       return ret;
 109     } else {
 110       return false;
 111     }
 112   }
 113 #endif
 114   return GetPriority() == kBackgroundPriority;
 115 }
 116
 117 bool Process::SetProcessBackgrounded(bool background) {
 118   DCHECK(IsValid());
 119
 120 #if defined(OS_CHROMEOS)
 121   if (cgroups.Get().enabled) {
 122     std::string pid = StringPrintf("%d", process_);
 123     const base::FilePath file =
 124         background ?
 125             cgroups.Get().background_file : cgroups.Get().foreground_file;
 126     return base::WriteFile(file, pid.c_str(), pid.size()) > 0;
 127   }
 128 #endif // OS_CHROMEOS
 129
 130   if (!CanBackgroundProcesses())
 131     return false;
 132
 133   int priority = background ? kBackgroundPriority : kForegroundPriority;
 134   int result = setpriority(PRIO_PROCESS, process_, priority);
 135   DPCHECK(result == 0);
 136   return result == 0;
 137 }
 138
 139 }  // namespace base