* Mathieu Desnoyers <[email protected]> wrote:
> I clearly expressed my position in the previous emails, so did you.
> You argued about a use of tracing that is not relevant to my vision of
> reality, which is :
>
> - Embedded systems developers won't want a breakpoint-based probe
are you arguing that i'm trying to force breakpoint-based probing on
you? I dont. In fact i explicitly mentioned that i'd accept and support
a 5-byte NOP in the body of the marker, in the following mails:
"just go for [...] the 5-NOP variant"
http://marc.theaimsgroup.com/?l=linux-kernel&m=115859771924187&w=2
(my reply to your second proposal)
"or at most one NOP"
http://marc.theaimsgroup.com/?l=linux-kernel&m=115865412332230&w=2
(my reply to your third proposal)
"at most a NOP inserted"
http://marc.theaimsgroup.com/?l=linux-kernel&m=115886524224874&w=2
(my reply to your fifth proposal)
That enables the probe to be turned into a function call - not an INT3
breakpoint. Does it take some effort to implement that on your part?
Yes, of course, but getting code upstream is never easy, /especially/ in
cases where most of the users wont use a particular feature.
> - High performance computing users won't want a breakpoint-based probe
I am not forcing breakpoint-based probing, at all. I dont want _static,
build-time function call based_ probing, and there is a big difference.
And one reason why i want to avoid "static, build-time function call
based probing" is because high-performance computing users dont want any
overhead at all in the kernel fastpath.
> - djprobe is far away from being in an acceptable state on
> architectures with very inconvenient erratas (x86).
djprobes over a NOP marker are perfectly usable and safe: just add a
simple constraint to them to only allow a djprobes insertion if it
replaces a 5-byte NOP.
> - kprobe and djprobe cannot access local variables in every cases
it is possible with the marker mechanism i outlined before:
http://marc.theaimsgroup.com/?l=linux-kernel&m=115886524224874&w=2
have i missed to address any concern of yours?
Ingo
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