Experimental 'purging and suspending' backgrounded tabs behind the flag

chrome/browser/memory/tab_manager.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 "chrome/browser/memory/tab_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 23 matching lines @@
 #include "chrome/browser/memory/tab_manager_web_contents_data.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_iterator.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/tabs/tab_utils.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_features.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/url_constants.h"
 #include "components/metrics/system_memory_stats_recorder.h"
 #include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/memory_pressure_controller.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/page_importance_signals.h"
 
@@ skipping 423 matching lines @@
     bool is_active_window = browser->window()->IsActive();
     AddTabStats(browser->tab_strip_model(), browser->is_app(), is_active_window,
                 stats_list);
   }
 }
 
 void TabManager::AddTabStats(const TabStripModel* model,
                              bool is_app,
                              bool active_model,
                              TabStatsList* stats_list) {
-for (int i = 0; i < model->count(); i++) {
+  for (int i = 0; i < model->count(); i++) {
     WebContents* contents = model->GetWebContentsAt(i);
     if (!contents->IsCrashed()) {
       TabStats stats;
       stats.is_app = is_app;
       stats.is_internal_page =
           IsInternalPage(contents->GetLastCommittedURL());
       stats.is_media = IsMediaTab(contents);
       stats.is_pinned = model->IsTabPinned(i);
       stats.is_selected = active_model && model->IsTabSelected(i);
       stats.is_discarded = GetWebContentsData(contents)->IsDiscarded();
@@ skipping 36 matching lines @@
         last_discard_time_ += suspend_time;
     }
   }
   last_adjust_time_ = NowTicks();
 
 #if defined(OS_CHROMEOS)
   TabStatsList stats_list = GetTabStats();
   // This starts the CrOS specific OOM adjustments in /proc/<pid>/oom_score_adj.
   delegate_->AdjustOomPriorities(stats_list);
 #endif
+
+  PurgeAndSuspendBackgroundedTabs();
+}
+
+void TabManager::PurgeAndSuspendBackgroundedTabs() {
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+  if (!command_line.HasSwitch(switches::kPurgeAndSuspendTime))
+    return;
+  int purge_and_suspend_time = 0;
+  if (!base::StringToInt(
+          command_line.GetSwitchValueASCII(switches::kPurgeAndSuspendTime),
+          &purge_and_suspend_time)) {
+    return;
+  }
+  if (purge_and_suspend_time <= 0)
+    return;
+  auto purge_and_suspend_time_delta = base::TimeDelta::FromSeconds(
+      purge_and_suspend_time);
+  auto tab_stats = GetUnsortedTabStats();
+  for (auto& tab : tab_stats) {
+    if (!tab.render_process_host->IsProcessBackgrounded())
+      continue;
+    // TODO(hajimehoshi): Now calling PurgeAndSuspend is implemented without
+    // timers for simplicity, so PurgeAndSuspend is called even after the
+    // renderer is purged and suspended once.
+    if (NowTicks() - tab.last_active < purge_and_suspend_time_delta)

[dcheng, 2016/05/10 04:49:53]

Nit: maybe just get NowTicks() once outside the loop and then just do a simple
comparison in here? e.g.

auto purge_and_suspend_threshhold  = NowTicks() -
base::TimeDelta::FromSeconds(purge_and_suspend_time);

for (...) {
  if (tab.last_active < purge_and_suspend_threshhold)
  /* ... */
}

[hajimehoshi, 2016/05/10 06:54:11]

Done.

+      continue;
+    tab.render_process_host->PurgeAndSuspend();
+  }
 }
 
 bool TabManager::CanDiscardTab(int64_t target_web_contents_id) const {
   TabStripModel* model;
   int idx = FindTabStripModelById(target_web_contents_id, &model);
 
   if (idx == -1)
     return false;
 
   WebContents* web_contents = model->GetWebContentsAt(idx);
@@ skipping 290 matching lines @@
     }
   } else {
     // The code here can only be tested under a full browser test.
     AddTabStats(&stats_list);
   }
 
   return stats_list;
 }
 
 }  // namespace memory