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SubjectRe: Results: pre6 vs pre6+zlatko's_patch vs pre5 vs arcavm13


On Sun, 10 Jan 1999, Andrea Arcangeli wrote:
>
> Steve, could you try the image test in 128Mbyte with this my new patch
> (arca-vm-14) applyed against clean 2.2.0-pre6?

Please don't do this.

> do {
> int result;
> - tsk->swap_address = address + PAGE_SIZE;
> result = try_to_swap_out(tsk, vma, address, pte, gfp_mask);
> + address += PAGE_SIZE;
> + tsk->swap_address = address;

The above is horribly broken, and should be killed on sight.

"swap_address" _must_ be set before try_to_swap_out(), because otherwise
when try-to_swap_out() sleeps any other processes trying to free will
start from the wrong address - unfairly penalizing the process in
question, as the accessed bits have been cleared.

If the above help, it only does so because it is unfair - which _can_ help
simply because other processes run faster.

It looks like you tried to optimize away one add, at the expense of
getting the whole algorithm wrong.

Linus


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