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SubjectRe: 2.1.120 sluggish![3~
   From: alan@lxorguk.ukuu.org.uk (Alan Cox)
Date: Tue, 8 Sep 1998 00:20:47 +0100 (BST)

> Are you using NFS? I'm assuming you are since you've been fixing it
> recently, does it crash if you leave NFS alone?
Tricky to tell. Its always using NFS extensively. /home is NFS.

I think people need to look at the swap changes.

One thing I have just noticed is that a (possibly important) invariant
has changed. Now there is one place in the kernel where
swap_duplicate() is called before a page is entered into the swap
cache. Consider the changes in read_swap_cache_async(), the ordering
is now:

if (!swap_duplicate(entry)) /* Account for the swap cache */
goto out_free_page;
if (!add_to_swap_cache(new_page, entry))
goto out_free_page;
Everywhere else the code does:

if ((entry = in_swap_cache(page_map))) {
...
swap_duplicate(entry);
}
Ie. always it is the case that the entry is in the swap cache before
it is duplicated. This invariant has been around for some time which
is why I look at it suspiciously. Whoops, I look again and there is
in fact one other place where the ordering is different
(vmscan.c:try_to_swap_out).

This could be a red herring, I'll look at it some more.

Later,
David S. Miller
davem@dm.cobaltmicro.com

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