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Stefania commented on CASSANDRA-8630: ------------------------------------- About byte ordering, it seems OHC insists on native byte ordering, which is little-endian on linux x86_64. Not a big problem, we can force the ordering to big-endian in the serializers. However, I think this means we always pay the price of swapping bytes when using direct byte buffers. Here is the implementation of {{getInt()}} in DirectByteBuffer.java: {code} private int getInt(long a) { if (unaligned) { int x = unsafe.getInt(a); return (nativeByteOrder ? x : Bits.swap(x)); } return Bits.getInt(a, bigEndian); } {code} Forcing byte ordering to big-endian doesn't mean {{nativeByteOrder}] becomes true: {code} public final ByteBuffer order(ByteOrder bo) { bigEndian = (bo == ByteOrder.BIG_ENDIAN); nativeByteOrder = (bigEndian == (Bits.byteOrder() == ByteOrder.BIG_ENDIAN)); return this; } {code} where {{Bits.byteOrder()}} return the platform endianess. So wouldn't we be better off forcing native byte ordering rather than big-endian? > Faster sequential IO (on compaction, streaming, etc) > ---------------------------------------------------- > > Key: CASSANDRA-8630 > URL: https://issues.apache.org/jira/browse/CASSANDRA-8630 > Project: Cassandra > Issue Type: Improvement > Components: Core, Tools > Reporter: Oleg Anastasyev > Assignee: Stefania > Labels: compaction, performance > Fix For: 3.x > > Attachments: 8630-FasterSequencialReadsAndWrites.txt, cpu_load.png, > flight_recorder_001_files.tar.gz > > > When node is doing a lot of sequencial IO (streaming, compacting, etc) a lot > of CPU is lost in calls to RAF's int read() and DataOutputStream's write(int). > This is because default implementations of readShort,readLong, etc as well as > their matching write* are implemented with numerous calls of byte by byte > read and write. > This makes a lot of syscalls as well. > A quick microbench shows than just reimplementation of these methods in > either way gives 8x speed increase. > A patch attached implements RandomAccessReader.read<Type> and > SequencialWriter.write<Type> methods in more efficient way. > I also eliminated some extra byte copies in CompositeType.split and > ColumnNameHelper.maxComponents, which were on my profiler's hotspot method > list during tests. > A stress tests on my laptop show that this patch makes compaction 25-30% > faster on uncompressed sstables and 15% faster for compressed ones. > A deployment to production shows much less CPU load for compaction. > (I attached a cpu load graph from one of our production, orange is niced CPU > load - i.e. compaction; yellow is user - i.e. not compaction related tasks) -- This message was sent by Atlassian JIRA (v6.3.4#6332)