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

Stephen C. Tweedie
1999-01-13T22:14:25Z

Hi,

On Wed, 13 Jan 1999 19:10:28 +0100 (CET), Andrea Arcangeli
<andrea@e-mind.com> said:

> On Wed, 13 Jan 1999, Rik van Riel wrote:
>> - in allocating swap space it just doesn't make sense to read
>> into the next swap 'region'

> The point is that I can't see a swap `region' looking at how
> scan_swap_map() works. The more atomic region I can see in the swap space
> is a block of bytes large PAGE_SIZE bytes (e.g. offset ;).

The whole point is that we try to swap adjacent virtual pages to
adjacent swap entries, so there is a good chance that nearby swap
entries are going to be useful when we page them back in again. Given
that adjacent swap entries on a swap partition are guaranteed to be
physically contiguous, it costs very little to swap in several nearby
elements at the same time, and we get a good chance of reading in useful
pages.

> For the case of binaries the aging on the page cache should take care of
> it (even if there's no aging on the swap cache as pre[567] if I remeber
> well).

There is no aging on the page cache at all other than the PG_referenced
bit.

--Stephen