Re: [patch] mm: pageable memory allocator (for DRM-GEM?)
From: Thomas HellstrÃm
Date: Thu Sep 25 2008 - 11:42:18 EST
Keith Packard wrote:
On Thu, 2008-09-25 at 00:19 -0700, Thomas HellstrÃm wrote:
If data is
dirtied in VRAM or the page(s) got discarded
we need new pages and to set up a copy operation.
Note that this can occur as a result of a suspend-to-memory transition
at which point *all* of the objects in VRAM will need to be preserved in
main memory, and so the pages aren't really 'freed', they just don't
need to have valid contents, but the system should be aware that the
space may be needed at some point in the future.
Actually, I think the pages must be allowed to be freed, and that we
don't put a requirement on "pageable" to keep
swap-space slots for these pages. If we hit an OOM-condition during
suspend-to-memory that's bad, but let's say we
required "pageable" to keep swap space slots for us, the result would
perhaps be that another device wasn't able to suspend, or a user-space
program was killed due to lack of swap-space prior to suspend.
I'm not really sure what's the worst situation, but my feeling is that
we should not require swap-space to be reserved for VRAM, and abort the
suspend operation if we hit OOM. That would, in the worst case, mean
that people with non-UMA laptops and a too small swap partition would
see their battery run out much quicker than they expected...
/Thomas
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