[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-04-21 15:43 -------
*** Bug 6434 has been marked as a duplicate of this bug. ***

-- 


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[Bug runtime/6432] New: use 2.6.26 probe_kernel_{read,write}

[fche at redhat dot com]

*** Bug 6433 has been marked as a duplicate of this bug. ***

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           Summary: use 2.6.26 probe_kernel_{read,write}
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com


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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-04-21 15:44 -------
*** Bug 6435 has been marked as a duplicate of this bug. ***

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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[joshua dot i dot stone at intel dot com]

------- Additional Comments From joshua dot i dot stone at intel dot com  2008-05-27 19:25 -------
Created an attachment (id=2757)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2757&action=view)
Use probe_kernel functions in deref macros

This changes the deref macros to use probe_kernel, but there's a performance
hit, probably due to no longer inlining the dereferencing activity.  Simple
benchmark scripts to follow...

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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[joshua dot i dot stone at intel dot com]

------- Additional Comments From joshua dot i dot stone at intel dot com  2008-05-27 19:30 -------
Created an attachment (id=2758)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2758&action=view)
Test the overhead of dereferencing numbers

Run as 'stap -gt deref-long.stp', and add '-DTEST_DIRECT' for direct memory
access.  My results on 2.6.26-rc3 x86_64:

OLD: 
direct: 1057min/1268avg/10905max
deref: 1073min/1305avg/9405max

NEW:
direct: 1050min/1235avg/9443max
deref: 1238min/1473avg/8850max

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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[joshua dot i dot stone at intel dot com]

------- Additional Comments From joshua dot i dot stone at intel dot com  2008-05-27 19:32 -------
Created an attachment (id=2759)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2759&action=view)
Test the overhead of dereferencing strings

Run as 'stap -gt deref-string.stp', and add '-DTEST_DIRECT' for direct memory
access.  My results on 2.6.26-rc3 x86_64:

OLD:
direct: 1725min/2072avg/10283max
deref: 1778min/2085avg/10950max

NEW:
direct: 1650min/2012avg/10613max
deref: 2152min/2476avg/12563max

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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[joshua dot i dot stone at intel dot com]

------- Additional Comments From joshua dot i dot stone at intel dot com  2008-05-27 19:40 -------
So given the performance disadvantage, is this still a change you want to 
make?  Or can anyone see a way to improve the efficiency?

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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-05-27 20:21 -------
Josh, thanks for trying this out.  Please commit the patch,
but #if-0'd out, so that some day we can easily try again,
and resolve/wontfix this bug.

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           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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[Bug runtime/6432] use 2.6.26 probe_kernel_{read,write}

[joshua dot i dot stone at intel dot com]

------- Additional Comments From joshua dot i dot stone at intel dot com  2008-05-27 23:33 -------
Committed in 2cda5f46cba978e19590efd7fee0b3075f8eb8df with the autoconf test
disabled.  One can use -DSTAPCONF_PROBE_KERNEL to enable it manually.

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