On Fri, Apr 13, 2007 at 12:21:25PM +1000, Nick Piggin wrote: > Matt Mackall wrote: > >On Fri, Apr 13, 2007 at 11:42:29AM +1000, Nick Piggin wrote: > > >>If kprobes is simply crappy and doesn't work properly for this, then I > >>could accept that. I'm not someone trying to get this info. So why can't > >>it be used? (not just for kpagemap, but for clear_refs and all that gunk > >>too). > > > > > >kprobes is good for looking at events, but bad for looking at state. > >Especially metric shitloads of state. > > Why? Why is a kprobes trap significantly more expensive than a read > syscall?
I guess I'm not clear on what you're proposing. From my understanding of kprobes (admittedly not an expert), this is hard to do and not a very good match. > >>Maybe. How about LRU? Reclaim performance is bad, and you want to work out > >>which pages keep going off the end of it, or which pages keep getting > >>written out via it, or who's pages are on the active list, forcing mine > >>out. > > > > > >Those are actually probably a good match for systemtap as they're all > >events. > > Traverse the LRU? Which files do they belong to? What process maps them? -ENOPARSE. -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
