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Further reduce memory overhead of PooledBufferAllocator 

… by lazily allocating PoolSubpages inside of the PoolArenas.
By default, a pooled allocator creates 32 arenas, and each arena, by default, makes room for 39 PoolSubpage size classes, which all told is 1.248 objects that serve no purpose other than as headers and locks for linked lists.
Each of these objects is at least 81 bytes, plus whatever the JVM adds on top.
This might not sound like much, but in our testing we'll be creating many thousands of allocators, and then it really adds up.
This commit is contained in:
Chris Vest 2021-05-21 15:37:59 +02:00
parent e6f867cc5f
commit 1c3b27f9e0
1 changed files with 23 additions and 11 deletions
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34
buffer-api/src/main/java/io/netty/buffer/api/pool/PoolArena.java
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@ -20,6 +20,8 @@ import io.netty.buffer.api.Buffer;
import io.netty.buffer.api.MemoryManager;
import io.netty.util.internal.StringUtil;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
@ -29,6 +31,7 @@ import static io.netty.buffer.api.pool.PoolChunk.isSubpage;
import static java.lang.Math.max;
class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl {
private static final VarHandle SUBPAGE_ARRAY = MethodHandles.arrayElementVarHandle(PoolSubpage[].class);
enum SizeClass {
Small,
Normal
@ -76,9 +79,6 @@ class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl
numSmallSubpagePools = nSubpages;
smallSubpagePools = newSubpagePoolArray(numSmallSubpagePools);
for (int i = 0; i < smallSubpagePools.length; i ++) {
smallSubpagePools[i] = newSubpagePoolHead();
}
q100 = new PoolChunkList(this, null, 100, Integer.MAX_VALUE, chunkSize);
q075 = new PoolChunkList(this, q100, 75, 100, chunkSize);
@ -135,7 +135,7 @@ class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl
* Synchronize on the head. This is needed as {@link PoolChunk#allocateSubpage(int)} and
* {@link PoolChunk#free(long)} may modify the doubly linked list as well.
*/
final PoolSubpage head = smallSubpagePools[sizeIdx];
PoolSubpage head = findSubpagePoolHead(sizeIdx);
final boolean needsNormalAllocation;
synchronized (head) {
final PoolSubpage s = head.next;
@ -246,7 +246,15 @@ class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl
}
PoolSubpage findSubpagePoolHead(int sizeIdx) {
return smallSubpagePools[sizeIdx];
PoolSubpage head = (PoolSubpage) SUBPAGE_ARRAY.getVolatile(smallSubpagePools, sizeIdx);
if (head == null) {
head = newSubpagePoolHead();
if (!SUBPAGE_ARRAY.compareAndSet(smallSubpagePools, sizeIdx, null, head)) {
// We lost the race. Read the winning value.
head = (PoolSubpage) SUBPAGE_ARRAY.getVolatile(smallSubpagePools, sizeIdx);
}
}
return head;
}
@Override
@ -288,8 +296,9 @@ class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl
private static List<PoolSubpageMetric> subPageMetricList(PoolSubpage[] pages) {
List<PoolSubpageMetric> metrics = new ArrayList<>();
for (PoolSubpage head : pages) {
if (head.next == head) {
for (int i = 0, len = pages.length; i < len; i++) {
PoolSubpage head = (PoolSubpage) SUBPAGE_ARRAY.getVolatile(pages, i);
if (head == null || head.next == head) {
continue;
}
PoolSubpage s = head.next;
@ -432,8 +441,8 @@ class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl
private static void appendPoolSubPages(StringBuilder buf, PoolSubpage[] subpages) {
for (int i = 0; i < subpages.length; i ++) {
PoolSubpage head = subpages[i];
if (head.next == head) {
PoolSubpage head = (PoolSubpage) SUBPAGE_ARRAY.getVolatile(subpages, i);
if (head == null || head.next == head) {
continue;
}
@ -449,8 +458,11 @@ class PoolArena extends SizeClasses implements PoolArenaMetric, AllocatorControl
}
public void close() {
for (PoolSubpage page : smallSubpagePools) {
page.destroy();
for (int i = 0, len = smallSubpagePools.length; i < len; i++) {
PoolSubpage page = (PoolSubpage) SUBPAGE_ARRAY.getVolatile(smallSubpagePools, i);
if (page != null) {
page.destroy();
}
}
for (PoolChunkList list : new PoolChunkList[] {qInit, q000, q025, q050, q100}) {
list.destroy();