Re: MM deadlock [was: Re: arca-vm-8...]

Linus Torvalds
1999-01-25T00:30:43Z

On Sun, 24 Jan 1999, Alan Cox wrote:
>
> Being able to throw out page tables is something that is going to be needed
> too. As far as I can see that does not mean complexity. The Linux VM is
> very clean in its page handling, there is almost nothing in the page tables
> that cannot be flushed or dumped to disk if need be.

There _is_ a major problem: being able to swap out page tables means that
the thing that swaps them out _has_ to own the mm semaphore.

That's the right thing to do anyway, but it means, for example, that the
_only_ process that can page stuff out would be kswapd.

Who knows? Maybe I should just bite the bullet and make that the rule,
then we could forget about all the extra recursive semaphore crap too. And
it has other advantages - it can speed up the page fault handler (which
right now has to get the kernel lock for certain situations).

Once that is done, paging out page tables is not really a problem.

> There are real cases where grab large linear block is needed.

Nobody has so far shown a reasonable implementation where this would be
possible.

Linus

--
To unsubscribe, send a message with 'unsubscribe linux-mm my@address'
in the body to majordomo@kvack.org. For more info on Linux MM,
see: http://humbolt.geo.uu.nl/Linux-MM/