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[Bug tapsets/5167] port/include blktap scripts


http://sourceware.org/bugzilla/show_bug.cgi?id=5167

William Cohen <wcohen at redhat dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |wcohen at redhat dot com

--- Comment #1 from William Cohen <wcohen at redhat dot com> 2012-03-14 14:41:30 UTC ---
The blktap code has five example scripts:

countall.stp - display counts of all blktrace events
spectest.stp - test 'speculative tracing' support
iotop.stp - periodically display top I/O producers
topfile.stp - display read/write I/O accumulated by file
traceread.stp - trace read I/O for all or selected file

Each example needs blktrace running to trigger the data collection
because the tapset probes kernel.function("_blk_add_trace").  There
are some additional probes in the kernel for kernel.function
("__set_page_dirty_nobuffers").

Didn't get any counts for the countall.stp or the other example
scripts. The bundling of the default handler functions in in the
tapsets/blktrace.stp blocks the real ones in countall.stp script from
being used.

I was able to veryify that __blk_add_trace was operating with the
following script:

$ stap  -I tapsets -e 'global c probe kernel.function("__blk_add_trace") {
c[$what]++ } probe end {foreach (w+ in c) printf("c[0x%x] = %d\n", w, c[w]) }'
c[0x100001] = 2235
c[0x100002] = 2071
c[0x100004] = 164
c[0x100009] = 21
c[0x10000f] = 4470
c[0x110000c] = 164
c[0x1400007] = 162
c[0x1800008] = 162

partical list of things to fix:
       -break out the default handler functions into separate files
       -probe the tracepoint locations rather than __blk_add_trace
                 (reduce overhead and eliminate need for blktrace to run)
       -address the deref() and access to data structure issues
       -make spectest.stp use the existing speculative.stp

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