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https://issues.apache.org/jira/browse/HBASE-17623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15897162#comment-15897162
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CHIA-PING TSAI commented on HBASE-17623:
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bq. This case is not really possible right?
The compressAndEncryptDat will be null if there is no encryption/compression.
bq.Why this specific change is needed now? Why we can not continue to have the
type as byte[]? So may be then we will have to keep the size also? Offset will
be any way 0
Yes, I keep and reuse the onDiskBlockBytesWithHeader stream
bq. The PE run shows that the net run time decreases with this change right?
But ur above table shows the corresponding case GC is more? !
The powerful impact on the run time is the I/O, so the connection between GC
and run time was not explicit if there are too many other I/O work (ex.
compaction, wal).
Thank you for the feedback. [~anoop.hbase]
> Reuse the bytes array when building the hfile block
> ---------------------------------------------------
>
> Key: HBASE-17623
> URL: https://issues.apache.org/jira/browse/HBASE-17623
> Project: HBase
> Issue Type: Improvement
> Reporter: CHIA-PING TSAI
> Assignee: CHIA-PING TSAI
> Priority: Minor
> Fix For: 2.0.0, 1.4.0
>
> Attachments: after(snappy_hfilesize=5.04GB).png,
> after(snappy_hfilesize=755MB).png, before(snappy_hfilesize=5.04GB).png,
> before(snappy_hfilesize=755MB).png, HBASE-17623.branch-1.v0.patch,
> HBASE-17623.branch-1.v1.patch, HBASE-17623.branch-1.v2.patch,
> HBASE-17623.branch-1.v2.patch, HBASE-17623.v0.patch, HBASE-17623.v1.patch,
> HBASE-17623.v1.patch, HBASE-17623.v2.patch, memory allocation measurement.xlsx
>
>
> There are two improvements.
> # The onDiskBlockBytesWithHeader should maintain a bytes array which can be
> reused when building the hfile.
> # The onDiskBlockBytesWithHeader is copied to an new bytes array only when we
> need to cache the block.
> # If no block need to be cached, the uncompressedBlockBytesWithHeader will
> never be created.
> {code:title=HFileBlock.java|borderStyle=solid}
> private void finishBlock() throws IOException {
> if (blockType == BlockType.DATA) {
> this.dataBlockEncoder.endBlockEncoding(dataBlockEncodingCtx,
> userDataStream,
> baosInMemory.getBuffer(), blockType);
> blockType = dataBlockEncodingCtx.getBlockType();
> }
> userDataStream.flush();
> // This does an array copy, so it is safe to cache this byte array when
> cache-on-write.
> // Header is still the empty, 'dummy' header that is yet to be filled
> out.
> uncompressedBlockBytesWithHeader = baosInMemory.toByteArray();
> prevOffset = prevOffsetByType[blockType.getId()];
> // We need to set state before we can package the block up for
> cache-on-write. In a way, the
> // block is ready, but not yet encoded or compressed.
> state = State.BLOCK_READY;
> if (blockType == BlockType.DATA || blockType == BlockType.ENCODED_DATA)
> {
> onDiskBlockBytesWithHeader = dataBlockEncodingCtx.
> compressAndEncrypt(uncompressedBlockBytesWithHeader);
> } else {
> onDiskBlockBytesWithHeader = defaultBlockEncodingCtx.
> compressAndEncrypt(uncompressedBlockBytesWithHeader);
> }
> // Calculate how many bytes we need for checksum on the tail of the
> block.
> int numBytes = (int) ChecksumUtil.numBytes(
> onDiskBlockBytesWithHeader.length,
> fileContext.getBytesPerChecksum());
> // Put the header for the on disk bytes; header currently is
> unfilled-out
> putHeader(onDiskBlockBytesWithHeader, 0,
> onDiskBlockBytesWithHeader.length + numBytes,
> uncompressedBlockBytesWithHeader.length,
> onDiskBlockBytesWithHeader.length);
> // Set the header for the uncompressed bytes (for cache-on-write) --
> IFF different from
> // onDiskBlockBytesWithHeader array.
> if (onDiskBlockBytesWithHeader != uncompressedBlockBytesWithHeader) {
> putHeader(uncompressedBlockBytesWithHeader, 0,
> onDiskBlockBytesWithHeader.length + numBytes,
> uncompressedBlockBytesWithHeader.length,
> onDiskBlockBytesWithHeader.length);
> }
> if (onDiskChecksum.length != numBytes) {
> onDiskChecksum = new byte[numBytes];
> }
> ChecksumUtil.generateChecksums(
> onDiskBlockBytesWithHeader, 0, onDiskBlockBytesWithHeader.length,
> onDiskChecksum, 0, fileContext.getChecksumType(),
> fileContext.getBytesPerChecksum());
> }{code}
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