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Unified Diff: base/metrics/field_trial.cc

Issue 2530573002: Share field trial allocator on zygote-using Linuxes (Closed)
Patch Set: make handle read-only Created 4 years, 1 month ago
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Index: base/metrics/field_trial.cc
diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc
index eb4b05e3466ac2e5511e4508dd4f80c596c221b5..47fdc4c7904639c1fef0f02b452ecd1257c9703c 100644
--- a/base/metrics/field_trial.cc
+++ b/base/metrics/field_trial.cc
@@ -21,6 +21,10 @@
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
+#if defined(OS_POSIX)
+#include "base/posix/global_descriptors.h"
+#endif
+
namespace base {
namespace {
@@ -233,6 +237,14 @@ HANDLE CreateReadOnlyHandle(FieldTrialList::FieldTrialAllocator* allocator) {
return nullptr;
return dst;
}
+#elif defined(OS_POSIX) && !defined(OS_NACL)
Alexei Svitkine (slow) 2016/11/23 17:49:55 Instead of these #elif chains that are confusing -
lawrencewu 2016/11/23 18:59:44 Done.
+int CreateReadOnlyHandle(FieldTrialList::FieldTrialAllocator* allocator) {
+ SharedMemoryHandle new_handle;
+ allocator->shared_memory()->ShareReadOnlyToProcess(GetCurrentProcessHandle(),
+ &new_handle);
+ int fd = SharedMemory::GetFdFromSharedMemoryHandle(new_handle);
+ return fd;
Alexei Svitkine (slow) 2016/11/23 17:49:55 Nit: Merge with line above.
lawrencewu 2016/11/23 18:59:44 Done.
+}
#endif
} // namespace
@@ -737,15 +749,16 @@ void FieldTrialList::CreateTrialsFromCommandLine(
const char* field_trial_handle_switch) {
global_->create_trials_from_command_line_called_ = true;
-#if defined(OS_WIN) && !defined(OS_NACL)
if (cmd_line.HasSwitch(field_trial_handle_switch)) {
std::string arg = cmd_line.GetSwitchValueASCII(field_trial_handle_switch);
- int field_trial_handle = std::stoi(arg);
- HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle);
- bool result = CreateTrialsFromWindowsHandle(handle);
+#if defined(OS_WIN)
+ bool result = CreateTrialsFromWindowsSwitch(arg);
+ DCHECK(result);
+#elif defined(OS_POSIX) && !defined(OS_NACL)
+ bool result = CreateTrialsFromPosixSwitch(arg);
DCHECK(result);
- }
#endif
+ }
if (cmd_line.HasSwitch(switches::kForceFieldTrials)) {
bool result = FieldTrialList::CreateTrialsFromString(
@@ -767,6 +780,18 @@ void FieldTrialList::AppendFieldTrialHandleIfNeeded(
handles->push_back(global_->readonly_allocator_handle_);
}
}
+#elif defined(OS_POSIX) && !defined(OS_NACL)
+// static
+int FieldTrialList::FieldTrialHandle() {
+ if (!global_)
+ return -1;
+ if (kUseSharedMemoryForFieldTrials) {
+ InstantiateFieldTrialAllocatorIfNeeded();
+ if (global_->readonly_allocator_handle_ != -1)
+ return global_->readonly_allocator_handle_;
+ }
+ return -1;
+}
#endif
// static
@@ -802,6 +827,24 @@ void FieldTrialList::CopyFieldTrialStateToFlags(
global_->field_trial_allocator_->UpdateTrackingHistograms();
return;
}
+#elif defined(OS_POSIX) && !defined(OS_NACL)
+ // Use shared memory to pass the state if the feature is enabled, otherwise
+ // fallback to passing it via the command line as a string.
+ if (kUseSharedMemoryForFieldTrials) {
+ InstantiateFieldTrialAllocatorIfNeeded();
+ // If the readonly handle didn't get duplicated properly, then fallback to
+ // original behavior.
+ if (global_->readonly_allocator_handle_ == -1) {
+ AddForceFieldTrialsFlag(cmd_line);
+ return;
+ }
+
+ std::string field_trial_handle =
+ std::to_string(global_->readonly_allocator_handle_);
+ cmd_line->AppendSwitchASCII(field_trial_handle_switch, field_trial_handle);
+ global_->field_trial_allocator_->UpdateTrackingHistograms();
+ return;
+ }
#endif
AddForceFieldTrialsFlag(cmd_line);
@@ -892,9 +935,26 @@ size_t FieldTrialList::GetFieldTrialCount() {
#if defined(OS_WIN)
// static
-bool FieldTrialList::CreateTrialsFromWindowsHandle(HANDLE handle) {
+bool FieldTrialList::CreateTrialsFromWindowsSwitch(std::string cli_switch) {
+ int field_trial_handle = std::stoi(cli_switch);
+ HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle);
SharedMemoryHandle shm_handle(handle, GetCurrentProcId());
+ return FieldTrialList::CreateTrialsFromSharedMemoryHandle(shm_handle);
+}
+#elif defined(OS_POSIX) && !defined(OS_NACL)
+// static
+bool FieldTrialList::CreateTrialsFromPosixSwitch(std::string cli_switch) {
+ int fd_key = std::stoi(cli_switch);
+ int fd = GlobalDescriptors::GetInstance()->Get(fd_key);
+ SharedMemoryHandle shm_handle(fd, true);
+ return FieldTrialList::CreateTrialsFromSharedMemoryHandle(shm_handle);
+}
+#endif
+#if !defined(OS_NACL)
+// static
+bool FieldTrialList::CreateTrialsFromSharedMemoryHandle(
+ SharedMemoryHandle shm_handle) {
// shm gets deleted when it gets out of scope, but that's OK because we need
// it only for the duration of this method.
std::unique_ptr<SharedMemory> shm(new SharedMemory(shm_handle, true));
@@ -984,8 +1044,15 @@ void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() {
if (global_->field_trial_allocator_ != nullptr)
return;
+ SharedMemoryCreateOptions options;
+ options.size = kFieldTrialAllocationSize;
+ options.share_read_only = true;
+
std::unique_ptr<SharedMemory> shm(new SharedMemory());
- if (!shm->CreateAndMapAnonymous(kFieldTrialAllocationSize))
+ if (!shm->Create(options))
+ TerminateBecauseOutOfMemory(kFieldTrialAllocationSize);
+
+ if (!shm->Map(kFieldTrialAllocationSize))
TerminateBecauseOutOfMemory(kFieldTrialAllocationSize);
global_->field_trial_allocator_.reset(
@@ -997,7 +1064,7 @@ void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() {
AddToAllocatorWhileLocked(registered.second);
}
-#if defined(OS_WIN)
+#if defined(OS_WIN) || defined(OS_POSIX)
// Set |readonly_allocator_handle_| so we can pass it to be inherited and
// via the command line.
global_->readonly_allocator_handle_ =

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