Re: new swap cache regime

Stephen C. Tweedie (sct@redhat.com)
Fri, 25 Sep 1998 20:35:34 +0100


Hi,

On Fri, 25 Sep 1998 09:01:08 -0700, Bill Hawes <whawes@transmeta.com>
said:

> Hi Andrea,

> I think your patch is a bit off the mark, as there's no need to add
> new special code to reclaim pages from the swap cache. The shrink_mmap
> code already handles it -- that's the whole point to using an inode to
> anchor the swap cache.

> All that needs to be done to handle the case of a parent forking with
> swapped out pages is (1) leave the page in the swap cache if the
> swap_map count says it's still being used, and (2) remove the message
> about freeing pages from the swap cache, as these will now become
> rather more frequent.

And (3) ensure that for the write fault case, we force a COW even for
unshared pages if there are other swapped processes which share the same
swap entry.

My single patch for is_page_shared to make it include the swap count
when calculating sharing achieves that with minimal fuss, since the VM
is already fully capable of dealing with these cases as long as it is
told that the existing data in the swap cache should be preserved.

--Stephen

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