Re: [PATCH 0/13] maps: pagemap, kpagemap, and related cleanups

Nick Piggin
2007-04-13T02:19:07Z

Andrew Morton wrote:
> On Fri, 13 Apr 2007 11:42:29 +1000 Nick Piggin <nickpiggin@yahoo.com.au> wrote:

>>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.
>
>
> I guess we have static analysis versus dynamic. The interfaces which Matt
> is proposing are suited to answering the question "what is my memory being
> used for" (static). They're unlikely to be useful for answering the question
> "what's happening in the VM" (dynamic). Systemtap is probably better for the
> dynamic analysis.

"what is my memory being used for *now*" ;)

> I guess one could generate an answer to the static question with systemtap,
> by accumulating running counts across the application lifetime and then
> snapshotting them. Sounds hard though.

Can't you just traverse arbitrary kernel data structures at a given point
in time, exactly like the /proc/ call is doing?

--
SUSE Labs, Novell Inc.