Messages in this thread | | | Date | Sun, 21 Oct 2012 15:29:21 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 4/2] numa, mm: Rename the PROT_NONE fault handling functions |
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* Rik van Riel <riel@redhat.com> wrote:
> On 10/21/2012 08:50 AM, Ingo Molnar wrote: > > > >* Ingo Molnar <mingo@kernel.org> wrote: > > > >>>>I don't much care either way, but I was thinking walken > >>>>might want to use something similar to do WSS estimation, > >>>>in which case the NUMA name is just as wrong. > >>> > >>>That's a good point. I had not considered other uses of the > >>>same code. > >> > >>Renaming the functions for more clarity still makes sense IMO: > >>we could give it a _wss or _working_set prefix/postfix? > > > >So, to not drop your patch on the floor I've modified it as per > >the patch below. > > > >The _wss() names signal that these handlers are used for a > >specific purpose, they are not related to the regular PROT_NONE > >handling code. > > Michel indicated that he does not use PROT_NONE for his > working set estimation code, but instead checks the accessed > bits in the page tables.
The pte_young() WSS method has a couple of fundamental limitations:
- it doesn't work with shared memory very well, the pte is per mapping, not per page. The PROT_NONE method instruments the physical page in essence.
- it does not tell us which task touched the pte, in a multi-threaded program
So like Peter I'd too expect these new WSS methods to eventually be picked up for any serious WSS work.
Thanks,
Ingo
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