Re: [PATCH] 2.5.28: VM strict overcommit

Alan Cox (alan@redhat.com)
Thu, 25 Jul 2002 04:18:14 -0400 (EDT)


> if (!vm_enough_memory((maxpos - inode->i_size) >> PAGE_SHIFT)) {
> err = -ENOMEM;
> goto out_nc;
> }
> }
>
> tmpfs supports holes. Looks to me like a small write which creates
> a big hole will be severely over-accounted for?

Intentionally. The base tree doesn't support page cache removal AS callbacks
so cannot support the ideal behaviour. The other rounding bits for the
tmpfs stuff are I think all fixed in 2.4 by Hugh's stuff, but fixing 2.5
tmpfs is an ongoing seperate project.

> vm_enough_memory() looks really slow. I'll bench this a bit.

On the benches I've run I can't see any difference whatever the
accounting mode I am using.

> of memory is dirty" is junk. It really wants to know more
> information about the dynamic state of the system. So tracking
> all those datums on-the-fly would be handy. One day.

We need it three years ago not "one day"

Alan
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