Bump field trial allocator size to 128 KiB

base/metrics/field_trial.cc

 // Copyright (c) 2012 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 "base/metrics/field_trial.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/base_switches.h"
@@ skipping 26 matching lines @@
 // Use shared memory to communicate field trial (experiment) state. Set to false
 // for now while the implementation is fleshed out (e.g. data format, single
 // shared memory segment). See https://codereview.chromium.org/2365273004/ and
 // crbug.com/653874
 const bool kUseSharedMemoryForFieldTrials = true;
 
 // Constants for the field trial allocator.
 const char kAllocatorName[] = "FieldTrialAllocator";
 const uint32_t kFieldTrialType = 0xABA17E13 + 2;  // SHA1(FieldTrialEntry) v2
 
-// We allocate 64 KiB to hold all the field trial data. This should be enough,
-// as currently we use ~8KiB for the field trials, and ~10KiB for experiment
-// parameters (as of 9/11/2016). This also doesn't allocate all 64 KiB at once
-// -- the pages only get mapped to physical memory when they are touched. If the
-// size of the allocated field trials does get larger than 64 KiB, then we will
-// drop some field trials in child processes, leading to an inconsistent view
-// between browser and child processes and possibly causing crashes (see
-// crbug.com/661617).
+// We allocate 128 KiB to hold all the field trial data. This should be enough,
+// as most people use 3 - 25 KiB for field trials (as of 11/25/2016).
+// This also doesn't allocate all 128 KiB at once -- the pages only get mapped
+// to physical memory when they are touched. If the size of the allocated field
+// trials does get larger than 128 KiB, then we will drop some field trials in
+// child processes, leading to an inconsistent view between browser and child
+// processes and possibly causing crashes (see crbug.com/661617).
 #if !defined(OS_NACL)
-const size_t kFieldTrialAllocationSize = 64 << 10;  // 64 KiB
+const size_t kFieldTrialAllocationSize = 128 << 10;  // 128 KiB
 #endif
 
 // We create one FieldTrialEntry per field trial in shared memory, via
 // AddToAllocatorWhileLocked. The FieldTrialEntry is followed by a base::Pickle
 // object that we unpickle and read from. Any changes to this structure requires
 // a bump in kFieldTrialType id defined above.
 struct FieldTrialEntry {
   // Expected size for 32/64-bit check.
   static constexpr size_t kExpectedInstanceSize = 8;
 
@@ skipping 1041 matching lines @@
     return;
   }
   AutoLock auto_lock(global_->lock_);
   CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name();
   trial->AddRef();
   trial->SetTrialRegistered();
   global_->registered_[trial->trial_name()] = trial;
 }
 
 }  // namespace base