Re: [9fans] crosstool fails on gentoo

["Iruata Souza" <iru.muzgo@gmail.com>]

On Mon, Jun 2, 2008 at 8:21 PM, ron minnich <rminnich@gmail.com> wrote:
> On Mon, Jun 2, 2008 at 4:00 PM, Iruata Souza <iru.muzgo@gmail.com> wrote:
>
>> I don't have any solaris boxes to play now, but I remember when taking
>> a dtrace course - more or less two years ago - that I managed to see
>> the performance of a nice machine go down only by setting all it's
>> tracing points. I know that this could be considered normal if it
>> wasn't for the fact that, with two xterms opened, the one which
>> started dtrace, after a series of ^C, had 'transfered' to it the
>> command-line history of the other xterm. It was a peculiar situation
>> since the instructor was telling us about the non-intrusiveness of the
>> tool.
>>
>
> it's worth reading the papers. Dtrace is quite capable.
>
> But look at the issues. You are taking a piece of code and splicing in
> another piece of code. It can get fun. What if someone was running the
> code you are splicing (think: SMP). What about time to remove it: make
> sure that (a) nobody is running the spliced in code (how do you do
> that in the general case) and (b) nobody is trying to run where you
> are putting the code back. What if the original code had an INT
> instruction? What if it tickled an  IRQ? What if code you spliced in
> takes a fault?
>
> Check out the kprobes device in linux to see how nasty it can get.
>
> At the same time, people delivering software to end users make good
> use of dtrace, so it's kind of hard to fault Sun for putting it in
> there -- they do have paychecks to hand out. And I expect that lots of
> customers demand that it stay in there ...
>

just like many people, I have made good use of dtrace myself. but the
need for a tool like that seems to me one more evidence of the trend
in talk about in your first post. in the pile of layers one has to dig
to find/fix/rework something, sometimes dtrace seems like the better -
or even the only one at hand - thing to deal with it.
put short: dtrace-like tools are good but, in general, having the need
for it is not.

iru