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Implement an LRU-SP eviction policy for the memory cache (bug 188458). r=gordon, sr=darin.

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git-svn-id: svn://10.0.0.236/trunk@139625 18797224-902f-48f8-a5cc-f745e15eee43
This commit is contained in:
bryner%netscape.com
2003-03-17 23:22:29 +00:00
parent ea0fe56e05
commit 46e842db3d
2 changed files with 76 additions and 14 deletions
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78
mozilla/netwerk/cache/src/nsMemoryCacheDevice.cpp vendored
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@@ -20,6 +20,7 @@
* Contributor(s):
* Gordon Sheridan, <gordon@netscape.com>
* Patrick C. Beard <beard@netscape.com>
* Brian Ryner <bryner@netscape.com>
*/
#include "nsMemoryCacheDevice.h"
@@ -29,21 +30,29 @@
#include "nsICacheVisitor.h"
#include "nsCRT.h"
// The memory cache implements the "LRU-SP" caching algorithm described in
// "LRU-SP: A Size-Adjusted and Popularity-Aware LRU Replacement Algorithm
// for Web Caching" by Kai Cheng and Yahiko Kambayashi.
// We keep ceil(log2(mHardLimit+1)) LRU queues. The queues hold exponentially
// increasing ranges of floor(log2((size/nref))) values for entries.
const char *gMemoryDeviceID = "memory";
nsMemoryCacheDevice::nsMemoryCacheDevice()
: mInitialized(PR_FALSE),
mEvictionList(nsnull),
mEvictionThreshold(40 * 1024),
mHardLimit(4 * 1024 * 1024), // set default memory limit, in case prefs aren't available
mTotalSize(0),
mInactiveSize(0),
mEntryCount(0),
mMaxEntryCount(0)
mMaxEntryCount(0),
mQueueCount(0)
{
PR_INIT_CLIST(&mEvictionList[mostLikelyToEvict]);
PR_INIT_CLIST(&mEvictionList[leastLikelyToEvict]);
// mEvictionList is created lazily to avoid re-creating it if the
// capacity is set immediately.
}
@@ -79,7 +88,7 @@ nsMemoryCacheDevice::Shutdown()
// evict all entries
nsCacheEntry * entry, * next;
for (int i=mostLikelyToEvict; i <= leastLikelyToEvict; ++i) {
for (int i = mQueueCount - 1; i >= 0; --i) {
entry = (nsCacheEntry *)PR_LIST_HEAD(&mEvictionList[i]);
while (entry != &mEvictionList[i]) {
NS_ASSERTION(entry->IsInUse() == PR_FALSE, "### shutting down with active entries.\n");
@@ -105,6 +114,10 @@ nsMemoryCacheDevice::Shutdown()
NS_ASSERTION(mEntryCount == 0, "### mem cache leaking entries?\n");
mInitialized = PR_FALSE;
delete[] mEvictionList;
mEvictionList = nsnull;
return NS_OK;
}
@@ -124,6 +137,7 @@ nsMemoryCacheDevice::FindEntry(nsCString * key)
// move entry to the tail of an eviction list
PR_REMOVE_AND_INIT_LINK(entry);
EnsureEvictionLists();
PR_APPEND_LINK(entry, &mEvictionList[EvictionList(entry, 0)]);
mInactiveSize -= entry->Size();
@@ -167,6 +181,7 @@ nsMemoryCacheDevice::BindEntry(nsCacheEntry * entry)
NS_ASSERTION(PR_CLIST_IS_EMPTY(entry),"entry is already on a list!");
// append entry to the eviction list
EnsureEvictionLists();
PR_APPEND_LINK(entry, &mEvictionList[EvictionList(entry, 0)]);
// add entry to hashtable of mem cache entries
@@ -289,6 +304,7 @@ nsMemoryCacheDevice::OnDataSizeChange( nsCacheEntry * entry, PRInt32 deltaSize)
if (!entry->IsDoomed()) {
// move entry to the tail of the appropriate eviction list
PR_REMOVE_AND_INIT_LINK(entry);
EnsureEvictionLists();
PR_APPEND_LINK(entry, &mEvictionList[EvictionList(entry, deltaSize)]);
}
@@ -303,7 +319,26 @@ nsMemoryCacheDevice::AdjustMemoryLimits(PRInt32 softLimit, PRInt32 hardLimit)
{
mSoftLimit = softLimit;
mHardLimit = hardLimit;
// First, evict entries that won't fit into the new cache size.
EvictEntriesIfNecessary();
// Create the eviction list array at the new size and then insert
// all of the entries into it.
PRInt32 oldQueueCount = mQueueCount;
PRCList* oldEvictionList = mEvictionList;
CreateEvictionLists();
for (PRInt32 i = PR_MIN(oldQueueCount, mQueueCount) - 1; i >= 0; --i) {
nsCacheEntry* entry = (nsCacheEntry*) PR_LIST_HEAD(&oldEvictionList[i]);
while (entry != &oldEvictionList[i]) {
nsCacheEntry* next = (nsCacheEntry*) PR_NEXT_LINK(entry);
PR_APPEND_LINK(entry, &mEvictionList[i]);
entry = next;
}
}
delete[] oldEvictionList;
}
@@ -334,7 +369,7 @@ nsMemoryCacheDevice::EvictEntriesIfNecessary(void)
if ((mTotalSize < mHardLimit) && (mInactiveSize < mSoftLimit))
return;
for (int i=mostLikelyToEvict; i<=leastLikelyToEvict; ++i) {
for (int i = mQueueCount - 1; i >= 0; --i) {
entry = (nsCacheEntry *)PR_LIST_HEAD(&mEvictionList[i]);
while (entry != &mEvictionList[i]) {
if (entry->IsInUse()) {
@@ -357,10 +392,14 @@ int
nsMemoryCacheDevice::EvictionList(nsCacheEntry * entry, PRInt32 deltaSize)
{
PRInt32 size = deltaSize + (PRInt32)entry->Size();
if ((size > mEvictionThreshold) || (entry->ExpirationTime() != NO_EXPIRATION_TIME))
return mostLikelyToEvict;
return leastLikelyToEvict;
// favor items which never expire by putting them in the lowest-index queue
if (entry->ExpirationTime() == NO_EXPIRATION_TIME)
return 0;
// compute which eviction queue this entry should go into, based on
// floor(log2(size/nref))
return PR_FloorLog2(size / (entry->FetchCount() + 1));
}
@@ -381,7 +420,7 @@ nsMemoryCacheDevice::Visit(nsICacheVisitor * visitor)
nsCacheEntry * entry;
nsCOMPtr<nsICacheEntryInfo> entryRef;
for (int i=mostLikelyToEvict; i <= leastLikelyToEvict; ++i) {
for (int i = mQueueCount - 1; i >= 0; --i) {
entry = (nsCacheEntry *)PR_LIST_HEAD(&mEvictionList[i]);
while (entry != &mEvictionList[i]) {
nsCacheEntryInfo * entryInfo = new nsCacheEntryInfo(entry);
@@ -406,7 +445,7 @@ nsMemoryCacheDevice::EvictEntries(const char * clientID)
nsCacheEntry * entry;
PRUint32 prefixLength = (clientID ? strlen(clientID) : 0);
for (int i=mostLikelyToEvict; i<=leastLikelyToEvict; ++i) {
for (int i = mQueueCount - 1; i >= 0; --i) {
PRCList * elem = PR_LIST_HEAD(&mEvictionList[i]);
while (elem != &mEvictionList[i]) {
entry = (nsCacheEntry *)elem;
@@ -436,6 +475,23 @@ nsMemoryCacheDevice::SetCapacity(PRInt32 capacity)
AdjustMemoryLimits(softLimit, hardLimit);
}
inline void
nsMemoryCacheDevice::EnsureEvictionLists()
{
if (!mEvictionList)
CreateEvictionLists();
}
void
nsMemoryCacheDevice::CreateEvictionLists()
{
// Create log2 (mHardLimit + 1) LRU queues
mQueueCount = PR_CeilingLog2(mHardLimit + 1);
mEvictionList = new PRCList[mQueueCount];
for (int i = 0; i < mQueueCount; ++i)
PR_INIT_CLIST(&mEvictionList[i]);
}
/******************************************************************************
* nsMemoryCacheDeviceInfo - for implementing about:cache