RE: Avoiding *mandatory* overcommit...

From: David Schwartz (davids@webmaster.com)
Date: Thu Mar 30 2000 - 23:02:18 EST


> One would assume the kernel always maintains at least 1
> page for its own
> paging purposes. So I touch my swapped out page. The kernel
> reads my page into
> the 'last page', and immediately pages out some other page,
> regaining its "last
> page". Repeat as necessary. It's a memory thrashing situation,
> but not fatal.

        Fine, until some process touches a COW page and then the one spare page is
gone. Just because you reserved the space for COW doesn't mean that
something else won't come along and grab the space you reserved before you
get a chance to. If you earmark swap pages for COW and don't let anything
else touch them, you'll have to kill processes when the kernel needs another
page even if there's plenty of free swap left. That doesn't seem to make a
lot of sense.

        DS

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