Re: [RFC 1/3] Framework for accurate node based statistics

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Christoph Lameter wrote:
On Thu, 8 Dec 2005, Nick Piggin wrote:


Christoph Lameter wrote:

On Wed, 7 Dec 2005, Nick Piggin wrote:

Sorry, I think I meant: why don't you just use the "add all counters
from all per-cpu of the node" in order to find the node-statistic?

which function is that?


I'm thinking of get_page_state_node... but that's not quite the same
thing. I guess sum all per-CPU counters from all zones in the node,
but that's going to be costly on big machines.


The per cpu counters count when a cpu did an allocation. They do not count on which node the allocation was done and are thereofre not useful to determine the memory use on one node.


Yes, not that exact function of course.


So I'm not sure, I guess I don't have any bright ideas... there is the
batching approach used by current pagecache_acct - is something like
that not sufficient either?


The framework provides a similar approach by keeping differential counters for each processor.


But the accounting delay has the unbounded error problem that the
batching approach does not.

--
SUSE Labs, Novell Inc.

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