Re: [patch 0/5] Support for sanitization flag in low-level page allocator

Ingo Molnar
2009-05-28T09:08:43Z

* Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> > > As for being swapped out - I do not believe that kernel stacks can
> > > ever be swapped out in Linux.
> >
> > yes, i referred to that as an undesirable option - because it slows
> > down pthread_create() quite substantially.
> >
> > This needs before/after pthread_create() benchmark results.
>
> kernel stacks can end up places you don't expect on hypervisor
> based systems.
>
> In most respects the benchmarks are pretty irrelevant - wiping
> stuff has a performance cost, but its the sort of thing you only
> want to do when you have a security requirement that needs it. At
> that point the performance is secondary.

Bechmarks, of course, are not irrelevant _at all_.

So i'm asking for this "clear kernel stacks on freeing" aspect to be
benchmarked thoroughly, as i expect it to have a negative impact -
otherwise i'm NAK-ing this. Please Cc: me to measurements results.

Thanks,

Ingo