disable field trials if the build is 30 days or older

net/disk_cache/backend_impl.cc

 // Copyright (c) 2010 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 "net/disk_cache/backend_impl.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/message_loop.h"
 #include "base/metrics/field_trial.h"
@@ skipping 164 matching lines @@
   // Field trials involve static objects so we have to do this only once.
   first = false;
   scoped_refptr<base::FieldTrial> trial1(
       new base::FieldTrial("CacheSize", 10));
   std::string group1 = base::StringPrintf("CacheSizeGroup_%d", size_group);
   trial1->AppendGroup(group1, base::FieldTrial::kAllRemainingProbability);
 
   scoped_refptr<base::FieldTrial> trial2(
       new base::FieldTrial("CacheThrottle", 100));
   int group2a = trial2->AppendGroup("CacheThrottle_On", 10);  // 10 % in.
-  trial2->AppendGroup("CacheThrottle_Off", 10);  // 10 % control.
+  trial2->AppendGroup("CacheThrottle_Off",
+      base::FieldTrial::kAllRemainingProbability);  // 90 % control.

[rvargas (doing something else), 2011/01/12 19:25:14]

This is not the same. The experiment has a control group, otherwise it is not
possible to really make any assertion about what's going on with the profiles
that are part of the experiment.

Why the need to have an extra group with all remaining users? It seems that it
only adds overhead (+ noise) everywhere.

[jar (doing other things), 2011/01/13 00:04:56]

As per our discussion....

We need some way to establish what a "reasonable" default would be.  The current
hack is to use the "all remaining probability" group to signal that.  Raman may
end up formalizing this in the constructor (as a new argument set), and that may
allow us to effectively reduce or turn-off trials under a variety of conditions
(old trials? reduce trial sets in Stable and beta?).  

To start any of this, we need a clear understanding of a "default" thing to do
when we effectively disable a trial.

On 2011/01/12 19:25:14, rvargas wrote:

 
   return trial2->group() == group2a;
 }
 
 // ------------------------------------------------------------------------
 
 // This class takes care of building an instance of the backend.
 class CacheCreator {
  public:
   CacheCreator(const FilePath& path, bool force, int max_bytes,
@@ skipping 1899 matching lines @@
     if (total_memory > kMaxBuffersSize || total_memory <= 0)
       total_memory = kMaxBuffersSize;
 
     done = true;
   }
 
   return static_cast<int>(total_memory);
 }
 
 }  // namespace disk_cache