lkml.org 
[lkml]   [2006]   [Sep]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Linux Kernel Markers
Mathieu Desnoyers wrote:
> * Vara Prasad (prasadav@us.ibm.com) wrote:
>> Martin Bligh wrote:
>>
>>> [...]
>>> Depends what we're trying to fix. I was trying to fix two things:
>>>
>>> 1. Flexibility - kprobes seem unable to access all local variables etc
>>> easily, and go anywhere inside the function. Plus keeping low overhead
>>> for doing things like keeping counters in a function (see previous
>>> example I mentioned for counting pages in shrink_list).
>>>
>> Using tools like systemtap on can consult DWARF information and put
>> probes in the middle of the function and access local variables as well,
>> that is not the real problem. The issue here is compiler doesn't seem to
>> generate required DWARF information in some cases due to optimizations.
>> The other related problem is when there exists debug information, the
>> way to specify the breakpoint location is using line number which is not
>> maintainable, having a marker solves this problem as well. Your proposal
>> still doesn't solve the need for markers if i understood correctly.
>>
>
> His implementation makes a heavy use of a marker mechanism : this is exactly
> what permits to create the instrumented objects from the same source code, but
> with different #defines.

Djprobes don't depend on markers. Actually, markers help to find the
safe place to probe, but they are not necessary. At least, instructions
that are more than 4 byte are probable.

As Vara pointed out, we are developing the tools that find the
safe place for djprobes.


Satoshi OSHIMA

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-09-20 00:37    [W:0.121 / U:0.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site