[
https://issues.apache.org/jira/browse/HBASE-13259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15156520#comment-15156520
]
Anoop Sam John commented on HBASE-13259:
----------------------------------------
bq.buffers[i] = allocator.allocate(0, false);
This is just a 0 length dummy buffer. Can be a HBB always.
{code}
if (directByteBuffer) {
77 buffer =
fileChannel.map(java.nio.channels.FileChannel.MapMode.READ_WRITE, pos * size,
78 size);
79 } else {
80 buffer =
fileChannel.map(java.nio.channels.FileChannel.MapMode.READ_WRITE, pos * size,
81 0);
82 }
{code}
On this engine, we will always call with 'directByteBuffer' true right? Can we
throw Exception otherwise rather than creating 0 length BB?
It is bit ugly to have sync() API in ByteBufferAllocator.
{code}
public void sync() throws IOException {
153 if (fileChannel != null) {
154 if(bufferArray != null) {
155 bufferArray.sync();
156 }
157 }
158 }
{code}
Can be call force() on fileChannel? Depending on that, we may not need sync()
in ByteBufferArray as well.
// TODO: See if the SHARED mode can be created here
You checked. I think it is not advisable. It depends on the total data size and
the page hit/miss is going to decide the perf.
> mmap() based BucketCache IOEngine
> ---------------------------------
>
> Key: HBASE-13259
> URL: https://issues.apache.org/jira/browse/HBASE-13259
> Project: HBase
> Issue Type: New Feature
> Components: BlockCache
> Affects Versions: 0.98.10
> Reporter: Zee Chen
> Assignee: Zee Chen
> Priority: Critical
> Fix For: 2.0.0, 1.3.0
>
> Attachments: HBASE-13259-v2.patch, HBASE-13259.patch,
> HBASE-13259_v3.patch, ioread-1.svg, mmap-0.98-v1.patch, mmap-1.svg,
> mmap-trunk-v1.patch
>
>
> Of the existing BucketCache IOEngines, FileIOEngine uses pread() to copy data
> from kernel space to user space. This is a good choice when the total working
> set size is much bigger than the available RAM and the latency is dominated
> by IO access. However, when the entire working set is small enough to fit in
> the RAM, using mmap() (and subsequent memcpy()) to move data from kernel
> space to user space is faster. I have run some short keyval gets tests and
> the results indicate a reduction of 2%-7% of kernel CPU on my system,
> depending on the load. On the gets, the latency histograms from mmap() are
> identical to those from pread(), but peak throughput is close to 40% higher.
> This patch modifies ByteByfferArray to allow it to specify a backing file.
> Example for using this feature: set hbase.bucketcache.ioengine to
> mmap:/dev/shm/bucketcache.0 in hbase-site.xml.
> Attached perf measured CPU usage breakdown in flames graph.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
