/*
* Copyright 2016 higherfrequencytrading.com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package net.openhft.affinity;
import net.openhft.affinity.impl.NoCpuLayout;
import net.openhft.affinity.impl.VanillaCpuLayout;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.util.BitSet;
/**
* This utility class support locking a thread to a single core, or reserving a whole core for a
* thread.
*
* @author peter.lawrey
*/
public class AffinityLock implements Closeable {
// Static fields and methods.
public static final String AFFINITY_RESERVED = "affinity.reserved";
// TODO It seems like on virtualized platforms .availableProcessors() value can change at
// TODO runtime. We should think about how to adopt to such change
public static final int PROCESSORS = Runtime.getRuntime().availableProcessors();
public static final BitSet BASE_AFFINITY = Affinity.getAffinity();
public static final BitSet RESERVED_AFFINITY = getReservedAffinity0();
private static final Logger LOGGER = LoggerFactory.getLogger(AffinityLock.class);
private static final LockInventory LOCK_INVENTORY = new LockInventory(new NoCpuLayout(PROCESSORS));
static {
try {
if (new File("/proc/cpuinfo").exists()) {
cpuLayout(VanillaCpuLayout.fromCpuInfo());
}
} catch (IOException e) {
LOGGER.warn("Unable to load /proc/cpuinfo", e);
}
}
/**
* Logical ID of the CPU to which this lock belongs to.
*/
private final int cpuId;
/**
* CPU to which this lock belongs to is of general use.
*/
private final boolean base;
/**
* CPU to which this lock belongs to is reservable.
*/
private final boolean reservable;
/**
* An inventory build from the CPU layout which keeps track of the various locks belonging to
* each CPU.
*/
private final LockInventory lockInventory;
boolean bound = false;
@Nullable
Thread assignedThread;
Throwable boundHere;
AffinityLock(int cpuId, boolean base, boolean reservable, LockInventory lockInventory) {
this.lockInventory = lockInventory;
this.cpuId = cpuId;
this.base = base;
this.reservable = reservable;
}
/**
* Set the CPU layout for this machine. CPUs which are not mentioned will be ignored. <p>
* Changing the layout will have no impact on thread which have already been assigned. It only
* affects subsequent assignments.
*
* @param cpuLayout for this application to use for this machine.
*/
public static void cpuLayout(@NotNull CpuLayout cpuLayout) {
LOCK_INVENTORY.set(cpuLayout);
}
/**
* @return The current CpuLayout for the application.
*/
@NotNull
public static CpuLayout cpuLayout() {
return LOCK_INVENTORY.getCpuLayout();
}
private static BitSet getReservedAffinity0() {
String reservedAffinity = System.getProperty(AFFINITY_RESERVED);
if (BASE_AFFINITY != null && (reservedAffinity == null || reservedAffinity.trim().isEmpty())) {
BitSet reserverable = new BitSet(PROCESSORS);
reserverable.set(1, PROCESSORS, true);
reserverable.andNot(BASE_AFFINITY);
if (reserverable.isEmpty() && PROCESSORS > 1) {
LoggerFactory.getLogger(AffinityLock.class).info("No isolated CPUs found, so assuming CPUs 1 to {} available.", (PROCESSORS - 1));
reserverable = new BitSet(PROCESSORS);
// make the first CPU unavailable
reserverable.set(1, PROCESSORS - 1, true);
reserverable.set(0, false);
return reserverable;
}
return reserverable;
}
long[] longs = new long[1];
longs[0] = Long.parseLong(reservedAffinity, 16);
return BitSet.valueOf(longs);
}
/**
* Assign any free cpu to this thread.
*
* @return A handle for the current AffinityLock.
*/
public static AffinityLock acquireLock() {
return acquireLock(true);
}
/**
* Assign any free core to this thread. <p> In reality, only one cpu is assigned, the rest of
* the threads for that core are reservable so they are not used.
*
* @return A handle for the current AffinityLock.
*/
public static AffinityLock acquireCore() {
return acquireCore(true);
}
/**
* Assign a cpu which can be bound to the current thread or another thread. <p> This can be used
* for defining your thread layout centrally and passing the handle via dependency injection.
*
* @param bind if true, bind the current thread, if false, reserve a cpu which can be bound
* later.
* @return A handle for an affinity lock.
*/
public static AffinityLock acquireLock(boolean bind) {
return acquireLock(bind, -1, AffinityStrategies.ANY);
}
/**
* Assign a core(and all its cpus) which can be bound to the current thread or another thread.
* <p> This can be used for defining your thread layout centrally and passing the handle via
* dependency injection.
*
* @param bind if true, bind the current thread, if false, reserve a cpu which can be bound
* later.
* @return A handle for an affinity lock.
*/
public static AffinityLock acquireCore(boolean bind) {
return acquireCore(bind, -1, AffinityStrategies.ANY);
}
private static AffinityLock acquireLock(boolean bind, int cpuId, @NotNull AffinityStrategy... strategies) {
return LOCK_INVENTORY.acquireLock(bind, cpuId, strategies);
}
private static AffinityLock acquireCore(boolean bind, int cpuId, @NotNull AffinityStrategy... strategies) {
return LOCK_INVENTORY.acquireCore(bind, cpuId, strategies);
}
/**
* @return All the current locks as a String.
*/
@NotNull
public static String dumpLocks() {
return LOCK_INVENTORY.dumpLocks();
}
private static boolean areAssertionsEnabled() {
boolean debug = false;
assert debug = true;
return debug;
}
/**
* Assigning the current thread has a side effect of preventing the lock being used again until
* it is released.
*
* @param bind whether to bind the thread as well
* @param wholeCore whether to reserve all the thread in the same core.
*/
final void assignCurrentThread(boolean bind, boolean wholeCore) {
assignedThread = Thread.currentThread();
if (bind)
bind(wholeCore);
}
/**
* Bind the current thread to this reservable lock.
*/
public void bind() {
bind(false);
}
/**
* Bind the current thread to this reservable lock.
*
* @param wholeCore if true, also reserve the whole core.
*/
public void bind(boolean wholeCore) {
if (bound && assignedThread != null && assignedThread.isAlive())
throw new IllegalStateException("cpu " + cpuId + " already bound to " + assignedThread);
if (areAssertionsEnabled())
boundHere = new Throwable("Bound here");
if (wholeCore) {
lockInventory.bindWholeCore(cpuId);
} else if (cpuId >= 0) {
bound = true;
assignedThread = Thread.currentThread();
LOGGER.info("Assigning cpu {} to {}", cpuId, assignedThread);
}
if (cpuId >= 0) {
BitSet affinity = new BitSet();
affinity.set(cpuId, true);
Affinity.setAffinity(affinity);
}
}
final boolean canReserve() {
if (!LockCheck.isCpuFree(cpuId))
return false;
if (!reservable) return false;
if (assignedThread != null) {
if (assignedThread.isAlive()) {
return false;
}
LOGGER.warn("Lock assigned to {} but this thread is dead.", assignedThread);
}
return true;
}
/**
* Give another affinity lock relative to this one based on a list of strategies. <p> The
* strategies are evaluated in order to (like a search path) to find the next appropriate
* thread. If ANY is not the last strategy, a warning is logged and no cpu is assigned (leaving
* the OS to choose)
*
* @param strategies To determine if you want the same/different core/socket.
* @return A matching AffinityLock.
*/
public AffinityLock acquireLock(AffinityStrategy... strategies) {
return acquireLock(false, cpuId, strategies);
}
/**
* Release the current AffinityLock which can be discarded.
*/
public void release() {
lockInventory.release();
}
@Override
public void close() {
release();
}
@Override
protected void finalize() throws Throwable {
if (bound) {
LOGGER.warn("Affinity lock for " + assignedThread + " was discarded rather than release()d in a controlled manner.", boundHere);
release();
}
super.finalize();
}
/**
* @return unique id for this CPI or -1 if not allocated.
*/
public int cpuId() {
return cpuId;
}
/**
* @return Was a cpu found to bind this lock to.
*/
public boolean isAllocated() {
return cpuId >= 0;
}
/**
* @return Has this AffinityLock been bound?
*/
public boolean isBound() {
return bound;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
if (assignedThread != null)
sb.append(assignedThread).append(" alive=").append(assignedThread.isAlive());
else if (reservable)
sb.append("Reserved for this application");
else if (base)
sb.append("General use CPU");
else
sb.append("CPU not available");
return sb.toString();
}
}