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Increase the swapper id space from 16 bit to 21 bit.
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This means that the page cache can now have roughly 2 million files mapped, instead of the 32.768 it could handle before.
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@chrisvest
chrisvest committed Apr 27, 2018
1 parent f6f0f97 commit 3340c3e
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Showing 4 changed files with 52 additions and 54 deletions.
76 changes: 37 additions & 39 deletions community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/PageList.java
View file
Expand Up @@ -56,8 +56,6 @@ class PageList
public static final long MAX_PAGES = Integer.MAX_VALUE;

private static final int UNBOUND_LAST_MODIFIED_TX_ID = -1;
private static final int UNSIGNED_BYTE_MASK = 0xFF;
private static final long UNSIGNED_INT_MASK = 0xFFFFFFFFL;

// 40 bits for file page id
private static final long MAX_FILE_PAGE_ID = 0b11111111_11111111_11111111_11111111_11111111L;
Expand All @@ -66,8 +64,10 @@ class PageList
private static final int OFFSET_ADDRESS = 8; // 8 bytes
private static final int OFFSET_LAST_TX_ID = 16; // 8 bytes
private static final int OFFSET_FILE_PAGE_ID = 24; // 5 bytes
private static final int OFFSET_USAGE_COUNTER = 29; // 1 byte
private static final int OFFSET_SWAPPER_ID = 30; // 2 bytes
@SuppressWarnings( "unused" )
private static final int OFFSET_SWAPPER_ID = 29; // 2 bytes, plus the 5 high-bits from usage counter
@SuppressWarnings( "unused" )
private static final int OFFSET_USAGE_COUNTER = 31; // 1 byte, but only the 3 low bits.

// todo we can alternatively also make use of the lower 12 bits of the address field, because
// todo the addresses are page aligned, and we can assume them to be at least 4096 bytes in size.
Expand Down Expand Up @@ -178,7 +178,7 @@ private void clearMemorySimple( long baseAddress, long pageCount )
UnsafeUtil.putLong( address += Long.BYTES, initialLockWord ); // lock word
UnsafeUtil.putLong( address += Long.BYTES, 0 ); // pointer
UnsafeUtil.putLong( address += Long.BYTES, 0 ); // last tx id
UnsafeUtil.putLong( address += Long.BYTES, MAX_FILE_PAGE_ID );
UnsafeUtil.putLong( address += Long.BYTES, MAX_FILE_PAGE_ID << 24 );
}
}

Expand Down Expand Up @@ -247,21 +247,11 @@ private long offAddress( long pageRef )
return pageRef + OFFSET_ADDRESS;
}

private long offUsage( long pageRef )
{
return pageRef + OFFSET_USAGE_COUNTER;
}

private long offFilePageId( long pageRef )
{
return pageRef + OFFSET_FILE_PAGE_ID;
}

private long offSwapperId( long pageRef )
{
return pageRef + OFFSET_SWAPPER_ID;
}

public long tryOptimisticReadLock( long pageRef )
{
return OffHeapPageLock.tryOptimisticReadLock( offLock( pageRef ) );
Expand Down Expand Up @@ -348,12 +338,7 @@ public void initBuffer( long pageRef )

private byte getUsageCounter( long pageRef )
{
return UnsafeUtil.getByteVolatile( offUsage( pageRef ) );
}

private void setUsageCounter( long pageRef, byte count )
{
UnsafeUtil.putByteVolatile( offUsage( pageRef ), count );
return (byte) (UnsafeUtil.getLongVolatile( offFilePageId( pageRef ) ) & 0x07);
}

/**
Expand All @@ -362,11 +347,18 @@ private void setUsageCounter( long pageRef, byte count )
public void incrementUsage( long pageRef )
{
// This is intentionally left benignly racy for performance.
byte usage = getUsageCounter( pageRef );
long address = offFilePageId( pageRef );
long v = UnsafeUtil.getLongVolatile( address );
long usage = v & 0x07;
if ( usage < 4 ) // avoid cache sloshing by not doing a write if counter is already maxed out
{
usage++;
setUsageCounter( pageRef, usage );
// Use compareAndSwapLong to only actually store the updated count if nothing else changed
// in this word-line. The word-line is shared with the file page id, and the swapper id.
// Those fields are updated under guard of the exclusive lock, but we *might* race with
// that here, and in that case we would never want a usage counter update to clobber a page
// binding update.
UnsafeUtil.compareAndSwapLong( null, address, v, (v & 0xFFFFFFFF_FFFFFFF8L) + usage );
}
}

Expand All @@ -376,20 +368,21 @@ public void incrementUsage( long pageRef )
public boolean decrementUsage( long pageRef )
{
// This is intentionally left benignly racy for performance.
byte usage = getUsageCounter( pageRef );
long address = offFilePageId( pageRef );
long v = UnsafeUtil.getLongVolatile( address );
long usage = v & 0x07;
if ( usage > 0 )
{
usage--;
setUsageCounter( pageRef, usage );
// See `incrementUsage` about why we use `compareAndSwapLong`.
UnsafeUtil.compareAndSwapLong( null, address, v, (v & 0xFFFFFFFF_FFFFFFF8L) + usage );
}
return usage == 0;
}

public long getFilePageId( long pageRef )
{
int highByte = UnsafeUtil.getByte( offFilePageId( pageRef ) ) & UNSIGNED_BYTE_MASK;
long lowInt = UnsafeUtil.getInt( offFilePageId( pageRef ) + Byte.BYTES ) & UNSIGNED_INT_MASK;
long filePageId = (((long) highByte) << Integer.SIZE) | lowInt;
long filePageId = UnsafeUtil.getLong( offFilePageId( pageRef ) ) >>> 24;
return filePageId == MAX_FILE_PAGE_ID ? PageCursor.UNBOUND_PAGE_ID : filePageId;
}

Expand All @@ -400,9 +393,10 @@ private void setFilePageId( long pageRef, long filePageId )
throw new IllegalArgumentException(
format( "File page id: %s is bigger then max supported value %s.", filePageId, MAX_FILE_PAGE_ID ) );
}
byte highByte = (byte) (filePageId >> Integer.SIZE);
UnsafeUtil.putByte( offFilePageId( pageRef ), highByte );
UnsafeUtil.putInt( offFilePageId( pageRef ) + Byte.BYTES, (int) filePageId );
long address = offFilePageId( pageRef );
long v = UnsafeUtil.getLong( address );
filePageId = (filePageId << 24) + (v & 0xFFFFFF);
UnsafeUtil.putLong( address, filePageId );
}

long getLastModifiedTxId( long pageRef )
Expand All @@ -423,27 +417,31 @@ void setLastModifiedTxId( long pageRef, long modifierTxId )
UnsafeUtil.compareAndSetMaxLong( null, offLastModifiedTransactionId( pageRef ), modifierTxId );
}

public short getSwapperId( long pageRef )
public int getSwapperId( long pageRef )
{
return UnsafeUtil.getShort( offSwapperId( pageRef ) );
long v = UnsafeUtil.getLong( offFilePageId( pageRef ) ) >>> 3;
return (int) (v & 0b1_11111_11111_11111_11111); // 21 bits.
}

private void setSwapperId( long pageRef, short swapperId )
private void setSwapperId( long pageRef, int swapperId )
{
UnsafeUtil.putShort( offSwapperId( pageRef ), swapperId );
swapperId = swapperId << 3;
long address = offFilePageId( pageRef );
long v = UnsafeUtil.getLong( address ) & (~(0b1_11111_11111_11111_11111 << 3));
UnsafeUtil.putLong( address, v + swapperId );
}

public boolean isLoaded( long pageRef )
{
return getFilePageId( pageRef ) != PageCursor.UNBOUND_PAGE_ID;
}

public boolean isBoundTo( long pageRef, short swapperId, long filePageId )
public boolean isBoundTo( long pageRef, int swapperId, long filePageId )
{
return getSwapperId( pageRef ) == swapperId && getFilePageId( pageRef ) == filePageId;
}

public void fault( long pageRef, PageSwapper swapper, short swapperId, long filePageId, PageFaultEvent event )
public void fault( long pageRef, PageSwapper swapper, int swapperId, long filePageId, PageFaultEvent event )
throws IOException
{
if ( swapper == null )
Expand Down Expand Up @@ -476,7 +474,7 @@ private static IllegalArgumentException swapperCannotBeNull()
return new IllegalArgumentException( "swapper cannot be null" );
}

private static IllegalStateException cannotFaultException( long pageRef, PageSwapper swapper, short swapperId,
private static IllegalStateException cannotFaultException( long pageRef, PageSwapper swapper, int swapperId,
long filePageId, int currentSwapper, long currentFilePageId )
{
String msg = format(
Expand Down Expand Up @@ -509,7 +507,7 @@ private void evict( long pageRef, EvictionEvent evictionEvent ) throws IOExcepti
long filePageId = getFilePageId( pageRef );
evictionEvent.setFilePageId( filePageId );
evictionEvent.setCachePageId( pageRef );
short swapperId = getSwapperId( pageRef );
int swapperId = getSwapperId( pageRef );
if ( swapperId != 0 )
{
// If the swapper id is non-zero, then the page was not only loaded, but also bound, and possibly modified.
Expand Down
8 changes: 4 additions & 4 deletions community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/SwapperSet.java
View file
Expand Up @@ -45,7 +45,7 @@ final class SwapperSet
// The tombstone is used as a marker to reserve allocation entries that have been freed, but not yet vacuumed.
// An allocation cannot be reused until it has been vacuumed.
private static final SwapperMapping TOMBSTONE = new SwapperMapping( 0, null );
private static final int MAX_SWAPPER_ID = Short.MAX_VALUE;
private static final int MAX_SWAPPER_ID = (1 << 21) - 1;
private volatile SwapperMapping[] swapperMappings = new SwapperMapping[] { SENTINEL };
private final PrimitiveIntSet free = Primitive.intSet();
private final Object vacuumLock = new Object();
Expand All @@ -69,7 +69,7 @@ private SwapperMapping( int id, PageSwapper swapper )
/**
* Get the {@link SwapperMapping} for the given swapper id.
*/
SwapperMapping getAllocation( short id )
SwapperMapping getAllocation( int id )
{
checkId( id );
SwapperMapping swapperMapping = swapperMappings[id];
Expand Down Expand Up @@ -197,10 +197,10 @@ void vacuum( Consumer<IntPredicate> evictAllLoadedPagesCallback )
}
}

synchronized short countAvailableIds()
synchronized int countAvailableIds()
{
// the max id is one less than the allowed count, but we subtract one for the reserved id 0
short available = MAX_SWAPPER_ID;
int available = MAX_SWAPPER_ID;
available -= swapperMappings.length; // ids that are allocated are not available
available += free.size(); // add back the ids that are free to be reused
return available;
Expand Down
16 changes: 8 additions & 8 deletions community/io/src/test/java/org/neo4j/io/pagecache/impl/muninn/PageListTest.java
View file
Expand Up @@ -1369,7 +1369,7 @@ public long read( long fpId, long bufferAddress, int bufferSize ) throws IOExcep
public void pageMustBeLoadedAndBoundAfterFault() throws Exception
{
// exclusive lock implied by constructor
short swapperId = 1;
int swapperId = 1;
long filePageId = 42;
pageList.initBuffer( pageRef );
pageList.fault( pageRef, DUMMY_SWAPPER, swapperId, filePageId, PageFaultEvent.NULL );
Expand All @@ -1383,7 +1383,7 @@ public void pageMustBeLoadedAndBoundAfterFault() throws Exception
public void pageWith5BytesFilePageIdMustBeLoadedAndBoundAfterFault() throws Exception
{
// exclusive lock implied by constructor
short swapperId = 12;
int swapperId = 12;
long filePageId = Integer.MAX_VALUE + 1L;
pageList.initBuffer( pageRef );
pageList.fault( pageRef, DUMMY_SWAPPER, swapperId, filePageId, PageFaultEvent.NULL );
Expand All @@ -1405,7 +1405,7 @@ public long read( long filePageId, long bufferAddress, int bufferSize ) throws I
throw new IOException( "boo" );
}
};
short swapperId = 1;
int swapperId = 1;
long filePageId = 42;
pageList.initBuffer( pageRef );
try
Expand All @@ -1418,7 +1418,7 @@ public long read( long filePageId, long bufferAddress, int bufferSize ) throws I
assertThat( e.getMessage(), is( "boo" ) );
}
assertThat( pageList.getFilePageId( pageRef ), is( filePageId ) );
assertThat( pageList.getSwapperId( pageRef ), is( (short) 0 ) ); // 0 means not bound
assertThat( pageList.getSwapperId( pageRef ), is( 0 ) ); // 0 means not bound
assertTrue( pageList.isLoaded( pageRef ) );
assertFalse( pageList.isBoundTo( pageRef, swapperId, filePageId ) );
}
Expand Down Expand Up @@ -1631,16 +1631,16 @@ public void pageMustNotBeLoadedAfterSuccessfulEviction() throws Exception
public void pageMustNotBeBoundAfterSuccessfulEviction() throws Exception
{
pageList.unlockExclusive( pageRef );
short swapperId = swappers.allocate( DUMMY_SWAPPER );
int swapperId = swappers.allocate( DUMMY_SWAPPER );
doFault( swapperId, 42 ); // page now bound & exclusively locked
pageList.unlockExclusive( pageRef ); // no longer exclusively locked; can now be evicted
assertTrue( pageList.isBoundTo( pageRef, (short) 1, 42 ) );
assertTrue( pageList.isLoaded( pageRef ) );
assertThat( pageList.getSwapperId( pageRef ), is( (short) 1 ) );
assertThat( pageList.getSwapperId( pageRef ), is( 1 ) );
pageList.tryEvict( pageRef, EvictionRunEvent.NULL );
assertFalse( pageList.isBoundTo( pageRef, (short) 1, 42 ) );
assertFalse( pageList.isLoaded( pageRef ) );
assertThat( pageList.getSwapperId( pageRef ), is( (short) 0 ) );
assertThat( pageList.getSwapperId( pageRef ), is( 0 ) );
}

@Test
Expand Down Expand Up @@ -2071,7 +2071,7 @@ public void failToSetHigherThenSupportedFilePageIdOnFault() throws IOException
doFault( swapperId, Long.MAX_VALUE );
}

private void doFault( short swapperId, long filePageId ) throws IOException
private void doFault( int swapperId, long filePageId ) throws IOException
{
assertTrue( pageList.tryExclusiveLock( pageRef ) );
pageList.initBuffer( pageRef );
Expand Down
6 changes: 3 additions & 3 deletions community/io/src/test/java/org/neo4j/io/pagecache/impl/muninn/SwapperSetTest.java
View file
Expand Up @@ -188,12 +188,12 @@ public void freeOfIdZeroMustThrow()
public void mustKeepTrackOfAvailableSwapperIds()
{
PageSwapper swapper = new DummyPageSwapper( "a", 42 );
short initial = Short.MAX_VALUE - 1;
int initial = (1 << 21) - 2;
assertThat( set.countAvailableIds(), is( initial ) );
int id = set.allocate( swapper );
assertThat( set.countAvailableIds(), is( (short) (initial - 1) ) );
assertThat( set.countAvailableIds(), is( initial - 1 ) );
set.free( id );
assertThat( set.countAvailableIds(), is( (short) (initial - 1) ) );
assertThat( set.countAvailableIds(), is( initial - 1 ) );
set.vacuum( x -> {} );
assertThat( set.countAvailableIds(), is( initial ) );
}
Expand Down

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