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