Re: Per-Processor Data Paget

Scott Lurndal (slurn@griffin.engr.sgi.com)
Thu, 9 Dec 1999 10:50:33 -0800 (PST)

>
> On Thu, 9 Dec 1999, Alan Cox wrote:
>
> > Having access the the pid at a fixed address is as good as the %esp trick if
> > not better. Unfortunately it means you now have to rewrite it each context
> > switch or flush the TLB. Both of these suck. [...]
>
> it's not even possible - think about threads on different processors
> running at once. Which fixed address? Page tables are shared.
>
> -- mingo
>

It certainly can be done, and it has been done.

Only the page table containing the virt addr 0xc0000000 need be
different between multiple threads.

Page tables don't _have_ to be shared, either, they could,
instead be duplicated.

In this proposal, however, only the page directory need be
different, the page tables for all user virtual address pages
can be shared between threads which shared address spaces.

scott

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