On Mon, Jun 2, 2008 at 8:21 PM, ron minnich <[EMAIL PROTECTED]> wrote: > On Mon, Jun 2, 2008 at 4:00 PM, Iruata Souza <[EMAIL PROTECTED]> 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
