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https://issues.apache.org/jira/browse/HBASE-14940?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15071128#comment-15071128
]
stack commented on HBASE-14940:
-------------------------------
It looks like below only called on instantiation of UnsafeAccess...
{code}
if (theUnsafe != null) {
64 BYTE_ARRAY_BASE_OFFSET = theUnsafe.arrayBaseOffset(byte[].class);
71 BYTE_ARRAY_BASE_OFFSET = theUnsafe.arrayBaseOffset(byte[].class);
72 try {
73 // Using java.nio.Bits#unaligned() to check for
unaligned-access capability
74 Class<?> clazz = Class.forName("java.nio.Bits");
75 Method m = clazz.getDeclaredMethod("unaligned");
76 m.setAccessible(true);
77 unaligned = (boolean) m.invoke(null);
78 } catch (Exception e) {
79 unaligned = false;
80 }
{code}
i.e. we do the reflection once only?
Patch seems good otherwise.
> Make our unsafe based ops more safe
> -----------------------------------
>
> Key: HBASE-14940
> URL: https://issues.apache.org/jira/browse/HBASE-14940
> Project: HBase
> Issue Type: Bug
> Reporter: Anoop Sam John
> Assignee: Anoop Sam John
> Fix For: 2.0.0, 1.2.0, 1.3.0, 1.1.3, 0.98.17, 1.0.4
>
> Attachments: HBASE-14940.patch, HBASE-14940_branch-1.patch,
> HBASE-14940_branch-1.patch, HBASE-14940_branch-1.patch,
> HBASE-14940_branch-1.patch, HBASE-14940_v2.patch
>
>
> Thanks for the nice findings [~ikeda]
> This jira solves 3 issues with Unsafe operations and ByteBufferUtils
> 1. We can do sun unsafe based reads and writes iff unsafe package is
> available and underlying platform is having unaligned-access capability. But
> we were missing the second check
> 2. Java NIO is doing a chunk based copy while doing Unsafe copyMemory. The
> max chunk size is 1 MB. This is done for "A limit is imposed to allow for
> safepoint polling during a large copy" as mentioned in comments in Bits.java.
> We are also going to do same way
> 3. In ByteBufferUtils, when Unsafe is not available and ByteBuffers are off
> heap, we were doing byte by byte operation (read/copy). We can avoid this and
> do better way.
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