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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11660) Add support for hardware crc on ARM aarch64 architecture
Date Tue, 03 Mar 2015 18:38:06 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14345469#comment-14345469
] 

Colin Patrick McCabe commented on HADOOP-11660:
-----------------------------------------------

{code}
-#if (!defined(__FreeBSD__) && !defined(WINDOWS))
+#if (!defined(__FreeBSD__) && !defined(WINDOWS)) && !defined(__aarch64__)
{code}

I don't understand the logic here, can you explain?  What does pipelining have to do with
whether we are on ARM?  At minimum this needs a comment.  

{code}
       crc_update_func = crc32_zlib_sb8;
+#ifdef __aarch64__
+      if (likely(cached_cpu_supports_crc32))
+        crc_update_func = crc32_zlib_hardware;
+#endif
{code}

Can you just change the definition of {{crc32_zlib_sb8}} when __aarch64__ is defined?  We
should minimize the number of skid marks in the code.

> Add support for hardware crc on ARM aarch64 architecture
> --------------------------------------------------------
>
>                 Key: HADOOP-11660
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11660
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: native
>    Affects Versions: 3.0.0
>         Environment: ARM aarch64 development platform
>            Reporter: Edward Nevill
>            Assignee: Edward Nevill
>            Priority: Minor
>              Labels: performance
>             Fix For: 3.0.0
>
>         Attachments: jira-11660.patch
>
>   Original Estimate: 48h
>  Remaining Estimate: 48h
>
> This patch adds support for hardware crc for ARM's new 64 bit architecture
> The patch is completely conditionalized on __aarch64__
> I have only added support for the non pipelined version as I benchmarked the pipelined
version on aarch64 and it showed no performance improvement.
> The aarch64 version supports both Castagnoli and Zlib CRCs as both of these are supported
on ARM aarch64 hardwre.
> To benchmark this I modified the test_bulk_crc32 test to print out the time taken to
CRC a 1MB dataset 1000 times.
> Before:
> CRC 1048576 bytes @ 512 bytes per checksum X 1000 iterations = 2.55
> CRC 1048576 bytes @ 512 bytes per checksum X 1000 iterations = 2.55
> After:
> CRC 1048576 bytes @ 512 bytes per checksum X 1000 iterations = 0.57
> CRC 1048576 bytes @ 512 bytes per checksum X 1000 iterations = 0.57
> So this represents a 5X performance improvement on raw CRC calculation.



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