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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/performance_manager/graph/policies/bfcache_policy.h"
#include "base/functional/bind.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/weak_ptr.h"
#include "base/notreached.h"
#include "base/task/task_traits.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "components/performance_manager/public/features.h"
#include "components/performance_manager/public/graph/frame_node.h"
#include "components/performance_manager/public/graph/page_node.h"
#include "content/public/browser/back_forward_cache.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/web_contents.h"
namespace performance_manager::policies {
namespace {
// The foregrounded tab's cache limit on moderate memory pressure. The negative
// value means no limit.
int ForegroundCacheSizeOnModeratePressure() {
static constexpr base::FeatureParam<int>
foreground_cache_size_on_moderate_pressure{
&features::kBFCachePerformanceManagerPolicy,
"foreground_cache_size_on_moderate_pressure", 3};
return foreground_cache_size_on_moderate_pressure.Get();
}
// The backgrounded tab's cache limit on moderate memory pressure. The negative
// value means no limit.
int BackgroundCacheSizeOnModeratePressure() {
static constexpr base::FeatureParam<int>
background_cache_size_on_moderate_pressure{
&features::kBFCachePerformanceManagerPolicy,
"background_cache_size_on_moderate_pressure", 1};
return background_cache_size_on_moderate_pressure.Get();
}
// The foregrounded tab's cache limit on critical memory pressure. The negative
// value means no limit.
int ForegroundCacheSizeOnCriticalPressure() {
static constexpr base::FeatureParam<int>
foreground_cache_size_on_critical_pressure{
&features::kBFCachePerformanceManagerPolicy,
"foreground_cache_size_on_critical_pressure", 0};
return foreground_cache_size_on_critical_pressure.Get();
}
// The backgrounded tab's cache limit on critical memory pressure. The negative
// value means no limit.
int BackgroundCacheSizeOnCriticalPressure() {
static constexpr base::FeatureParam<int>
background_cache_size_on_critical_pressure{
&features::kBFCachePerformanceManagerPolicy,
"background_cache_size_on_critical_pressure", 0};
return background_cache_size_on_critical_pressure.Get();
}
bool PageMightHaveFramesInBFCache(const PageNode* page_node) {
// TODO(crbug.com/40182881): Use PageState when that actually works.
auto main_frame_nodes = page_node->GetMainFrameNodes();
if (main_frame_nodes.size() == 1)
return false;
for (const FrameNode* main_frame_node : main_frame_nodes) {
if (!main_frame_node->IsCurrent())
return true;
}
return false;
}
using MemoryPressureLevel = base::MemoryPressureListener::MemoryPressureLevel;
void MaybeFlushBFCacheImpl(content::WebContents* contents,
MemoryPressureLevel memory_pressure_level) {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
CHECK(contents);
int cache_size = -1;
content::BackForwardCache::NotRestoredReason reason;
bool foregrounded =
(contents->GetVisibility() == content::Visibility::VISIBLE);
switch (memory_pressure_level) {
case MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_MODERATE:
cache_size = foregrounded ? ForegroundCacheSizeOnModeratePressure()
: BackgroundCacheSizeOnModeratePressure();
reason = content::BackForwardCache::NotRestoredReason::
kCacheLimitPrunedOnModerateMemoryPressure;
break;
case MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_CRITICAL:
cache_size = foregrounded ? ForegroundCacheSizeOnCriticalPressure()
: BackgroundCacheSizeOnCriticalPressure();
reason = content::BackForwardCache::NotRestoredReason::
kCacheLimitPrunedOnCriticalMemoryPressure;
break;
default:
NOTREACHED();
}
// Do not flush BFCache if cache_size is negative (such as -1).
if (cache_size < 0)
return;
// Do not flush the BFCache if there's a pending navigation as this could stop
// it.
// TODO(sebmarchand): Check if this is really needed.
auto& navigation_controller = contents->GetController();
if (!navigation_controller.GetPendingEntry())
navigation_controller.GetBackForwardCache().Prune(cache_size, reason);
}
} // namespace
void BFCachePolicy::MaybeFlushBFCache(
const PageNode* page_node,
MemoryPressureLevel memory_pressure_level) {
DCHECK(page_node);
MaybeFlushBFCacheImpl(page_node->GetWebContents().get(),
memory_pressure_level);
}
void BFCachePolicy::OnPassedToGraph(Graph* graph) {
DCHECK(graph->HasOnlySystemNode());
graph->AddSystemNodeObserver(this);
}
void BFCachePolicy::OnTakenFromGraph(Graph* graph) {
graph->RemoveSystemNodeObserver(this);
}
void BFCachePolicy::OnMemoryPressure(MemoryPressureLevel new_level) {
// This shouldn't happen but add the check anyway in case the API changes.
if (new_level == MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_NONE) {
return;
}
// Apply the cache limit to all pages.
for (const PageNode* page_node : GetOwningGraph()->GetAllPageNodes()) {
if (PageMightHaveFramesInBFCache(page_node)) {
MaybeFlushBFCache(page_node, new_level);
}
}
}
} // namespace performance_manager::policies
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