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A recent change in systemtap's uprobes kernel module lets it skip singlestepping after a breakpoint on easily emulated instructions, especially NOPs.

http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=f2c6cb7149b317baa7e1cb66312febc4b1ae5f9f

This is significant for SDT, our userspace static probes, because those probes always insert a NOP for systemtap to put a breakpoint on.  Using our benchmark scripts/probe_perf/bench.sh, which measures the overhead of nearly 4 million probe hits, I get these elapsed times:

   not instrumented:  0.86s
   uprobes w/ sstep: 16.46s
  uprobes w/o sstep:  7.81s

I believe this is a very worthwhile and easy change to backport into RHEL's systemtap package.

This commit is needed to fix powerpc:

http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=8ea20756d7e3236da8aaee3f7db8cd76e5bbc3e6

We are also waiting on IBM folks to see if we need additions in powerpc's arch_validate_probed_insn().

uprobes_ppc: Don't emulate privileged MSR opcodes
http://sourceware.org/git/gitweb.cgi?p=systemtap.git;a=commit;h=51b7256

(FLW) I believe it's good to go...

Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.