Re: [RFC] Page table sharing

From: Daniel Phillips (phillips@bonn-fries.net)
Date: Mon Feb 18 2002 - 21:22:21 EST


On February 19, 2002 03:05 am, Linus Torvalds wrote:
> On Mon, 18 Feb 2002, Rik van Riel wrote:
> >
> > The swapout code can remove a page from the page table
> > while another process is in the process of unsharing
> > the page table.
>
> Ok, I'll buy that. However, looking at that, the locking is not the real
> issue at all:
>
> When the swapper does a "ptep_get_and_clear()" on a shared pmd, it will
> end up having to not just synchronize with anybody doing unsharing, it
> will have to flush all the TLB's on all the mm's that might be implicated.
>
> Which implies that the swapper needs to look up all mm's some way anyway,

Ick. With rmap this is straightforward, but without, what? flush_tlb_all?
Maybe page tables should be unshared on swapin/out after all, only on arches
that need special tlb treatment, or until we have rmap.

> so the locking gets solved that way.

-- 
Daniel
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