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