Re: [ckrm-tech] [RFC][PATCH 5/7] UBC: kernel memory accounting (core)

From: Kirill Korotaev
Date: Mon Aug 21 2006 - 04:52:01 EST

Dave Hansen wrote:
On Fri, 2006-08-18 at 12:12 +0400, Kirill Korotaev wrote:

LDT takes from 1 to 16 pages. and is allocated by vmalloc.
do you propose to replace it with slab which can fail due to memory

Nope. ;)
so what is your proposal then? Sorry, probably missed it due to lots of emails :)

the same applies to fdset, fdarray, ipc ids and iptables entries.

The vmalloc area, along with all of those other structures _have_ other
data structures. Now, it will take a wee bit more patching to directly
tag those thing with explicit container pointers (or accounting
references), but I would much prefer that, especially for the things
that are larger than a page.
do you mean that you prefer adding a explicit pointer to the structures

I worry that this approach was used instead of patching all of the
individual subsystems because this was easier to maintain as an
out-of-tree patch, and it isn't necessarily the best approach.
:) if we were to optimize for patch size then we would select vserver
approach and be happy...

Dave, we used to add UBC pointers on each data structure and then do
a separate accounting in the places where objects are allocated.
We spent a lot of time and investigation on how to make it better,
because it was leading to often accounting errors, wrong error paths etc.
The approach provided in this patchset proved to be much more efficient
and more error prone. And it is much much more elegant!

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