Disk cache: Don't evict entries if we are busy doing other stuff....

net/disk_cache/backend_impl.cc

 // Copyright (c) 2006-2008 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/histogram.h"
 #include "base/message_loop.h"
@@ skipping 748 matching lines @@
     AddStorageSize(new_size - old_size);
 
   // Update the usage statistics.
   stats_.ModifyStorageStats(old_size, new_size);
 }
 
 void BackendImpl::TooMuchStorageRequested(int32 size) {
   stats_.ModifyStorageStats(0, size);
 }
 
-std::string BackendImpl::HistogramName(const char* name, int experiment) {
+bool BackendImpl::IsLoaded() const {
+  CACHE_UMA(COUNTS, "PendingIO", GetSizeGroup(), num_pending_io_);
+  return num_pending_io_ > 10;
+}
+
+std::string BackendImpl::HistogramName(const char* name, int experiment) const {
   if (!experiment)
     return StringPrintf("DiskCache.%d.%s", cache_type_, name);
   return StringPrintf("DiskCache.%d.%s_%d", cache_type_, name, experiment);
 }
 
-int BackendImpl::GetSizeGroup() {
+int BackendImpl::GetSizeGroup() const {
   if (disabled_)
     return 0;
 
   // We want to report times grouped by the current cache size (50 MB groups).
   int group = data_->header.num_bytes / (50 * 1024 * 1024);
   if (group > 6)
     group = 6;  // Limit the number of groups, just in case.
   return group;
 }
 
@@ skipping 66 matching lines @@
   DCHECK(error <= 0);
   CACHE_UMA(CACHE_ERROR, "Error", 0, error * -1);
 }
 
 void BackendImpl::OnEvent(Stats::Counters an_event) {
   stats_.OnEvent(an_event);
 }
 
 void BackendImpl::OnStatsTimer() {
   stats_.OnEvent(Stats::TIMER);
+  int64 time = stats_.GetCounter(Stats::TIMER);
   int64 current = stats_.GetCounter(Stats::OPEN_ENTRIES);
-  int64 time = stats_.GetCounter(Stats::TIMER);
 
-  current = current * (time - 1) + num_refs_;
-  current /= time;
-  stats_.SetCounter(Stats::OPEN_ENTRIES, current);
-  stats_.SetCounter(Stats::MAX_ENTRIES, max_refs_);
+  // OPEN_ENTRIES is a sampled average of the number of open entries, avoiding
+  // the bias towards 0.
+  if (num_refs_ && (current != num_refs_)) {
+    int64 diff = (num_refs_ - current) / 50;
+    if (!diff)
+      diff = num_refs_ > current ? 1 : -1;
+    current = current + diff;
+    stats_.SetCounter(Stats::OPEN_ENTRIES, current);
+    stats_.SetCounter(Stats::MAX_ENTRIES, max_refs_);
+  }
+
+  CACHE_UMA(COUNTS, "NumberOfReferences", 0, num_refs_);

[Nicolas Sylvain, 2009/07/09 22:32:21]

still lgtm

 
   if (!data_)
     first_timer_ = false;
   if (first_timer_) {
     first_timer_ = false;
     if (ShouldReportAgain())
       ReportStats();
   }
 
   // Save stats to disk at 5 min intervals.
@@ skipping 684 matching lines @@
 
   return num_dirty;
 }
 
 bool BackendImpl::CheckEntry(EntryImpl* cache_entry) {
   RankingsNode* rankings = cache_entry->rankings()->Data();
   return !rankings->pointer;
 }
 
 }  // namespace disk_cache