SimpleCache: histogram queuing delays and I/O portion of more ops.

net/disk_cache/simple/simple_synchronous_entry.h

 // Copyright (c) 2013 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.
 
 #ifndef NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_
 
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 99 matching lines @@
     int index;
     int offset;
     int64_t sparse_offset;
     int buf_len;
     bool truncate;
     bool doomed;
   };
 
   // Opens a disk cache entry on disk. The |key| parameter is optional, if empty
   // the operation may be slower. The |entry_hash| parameter is required.
   // |had_index| is provided only for histograms.

[xunjieli, 2017/05/02 18:21:29]

can you add a comment here on when |start_time| refers to?
Could also consider renaming |start_time| to |queuing_start_time| to be more
explicit that the timestamp is when we post the Open/CreateEntry task to the
worker pool.

[Maks Orlovich, 2017/05/02 19:49:20]

Done.

   static void OpenEntry(net::CacheType cache_type,
                         const base::FilePath& path,
                         const std::string& key,
                         uint64_t entry_hash,
                         bool had_index,
+                        const base::TimeTicks& start_time,
                         SimpleEntryCreationResults* out_results);
 
   static void CreateEntry(net::CacheType cache_type,
                           const base::FilePath& path,
                           const std::string& key,
                           uint64_t entry_hash,
                           bool had_index,
+                          const base::TimeTicks& start_time,
                           SimpleEntryCreationResults* out_results);
 
   // Deletes an entry from the file system without affecting the state of the
   // corresponding instance, if any (allowing operations to continue to be
   // executed through that instance). Returns a net error code.
   static int DoomEntry(const base::FilePath& path, uint64_t entry_hash);
 
   // Like |DoomEntry()| above, except that it truncates the entry files rather
   // than deleting them. Used when dooming entries after the backend has
   // shutdown. See implementation of |SimpleEntryImpl::DoomEntryInternal()| for
@@ skipping 219 matching lines @@
   int64_t sparse_tail_offset_;
 
   // True if the entry was created, or false if it was opened. Used to log
   // SimpleCache.*.EntryCreatedWithStream2Omitted only for created entries.
   bool files_created_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_SYNCHRONOUS_ENTRY_H_