lkml.org 
[lkml]   [2016]   [Aug]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 10/10] fault injection: inject faults in new/rare callchains
From
Date
Hi,

On 08/08/2016 03:54 PM, Akinobu Mita wrote:
> 2016-08-04 0:05 GMT+09:00 Vegard Nossum <vegard.nossum@oracle.com>:
>> 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

\
 
 \ /
  Last update: 2016-08-08 16:41    [W:0.054 / U:0.384 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site