[Bug translator/14689] missing 'syscalls' tracepoints

["fche at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14689

--- Comment #1 from Frank Ch. Eigler <fche at redhat dot com> 2012-10-09 19:44:50 UTC ---
Note that stap does give access to the master tracepoints sys_enter and
sys_exit.  At one point, the demultiplexing done by the kernel for perf/ftrace
was such that there weren't really N low-level tracepoints that may be
individually turned on/off.  If any was turned on, the process incurred a
penalty for *every* syscall.  Demultiplexing was just a conditional
postprocessing phase, by which time the damage was already done.  It roughly
equivalent to

probe kernel.trace.sys_five = kernel.trace("sys_enter")
      { if ($syscall != 5) next; }

If this is still the case, then there is little point trying to connect to the
same demultiplexing widget.

See also bug #12748.

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