Hi,
On 08/08/2016 03:54 PM, Akinobu Mita wrote:
2016-08-04 0:05 GMT+09:00 Vegard Nossum <[email protected]>:
Before this patch, fault injection uses a combination of randomness and
frequency to determine where to inject faults. The problem with this is
that code paths which are executed very rarely get proportional amounts
of faults injected.
A better heuristic is to look at the actual callchain leading up to the
possible failure point; if we see a callchain that we've never seen up
until this point, chances are it's a rare one and we should definitely
inject a fault here (since we might not get the chance again later).
This uses a probabilistic set structure (similar to a bloom filter) to
determine whether we have seen a particular callchain before by hashing
the stack trace and atomically testing/setting a bit corresponding to
the current callchain.
[...]
+config FAULT_INJECTION_AT_NEW_CALLSITES
+ bool "Inject fault the first time at a new callsite"
Isn't it better to make a run time configurable option instead of the
build option?
I prefer a build option personally since it keeps the code simple (you
don't have to dynamically allocate the bitmap of known callchains, for
example). I figured most people using fault injection would enable the
new option while still allowing others to keep the current behaviour
if they really want to.
If you prefer a run-time option I can submit a new version.
Thanks,
Vegard
