Messages in this thread | | | Date | Fri, 13 Apr 2007 12:11:53 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH 0/13] maps: pagemap, kpagemap, and related cleanups |
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Matt Mackall wrote: > On Fri, Apr 13, 2007 at 11:01:41AM +1000, Nick Piggin wrote: > >>>Basically: to show what the hell's going on in the VM. >> >>kprobes / systemtap isn't good enough? > > > It's not really a good match to the kprobes model. I'm not interested > in events, per se. I don't want to need to know about every single > alloc/free of N different varieties integrated from boot onward to > build up an image of the state of the system. Instead, I want to take > snapshots of the state of the VM.
Systemtap can't output a large set of values?
Why can't you attach a kprobe to a dummy syscall, and from there iterate over pgdat/zone/memmap and output what you want?
Actually I'm surprised that kind of data querying facility isn't already in there (I haven't used it seriously though).
> The main goal here is to be able to answer the question "where's my > memory going?". Currently you can't really give a good answer to that > question from userspace because of shared mappings, etc. > > There are lots of secondary questions that follow on very quickly from > that, like "what parts of my shared mappings are or aren't shared, and > why?", "what's actually in my application's working set?" and "how much > of this crap can I ditch?".
I understand roughly what you want, and that you can't easily get it from /proc currently. My question at this point is just why can we not use systemtap.
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