On Tue, 2003-02-11 at 13:20, Andrew Morton wrote:
> 256 zones is fairly exorbitant. I suspect the number of machines which have
>
> a) more than 16 zones and
> b) CONFIG_SOFTWARE_SUSPEND
>
> is zero. So you can always munch into the top eight bits.
So bits <= 27 should be safe or are guaranteed safe? :> (Keep in mind
that people are starting to port swsusp to other archs)
> PG_checked is supposed to be removed - I have not looked into that. PG_slab
> is fairly optional.
AFAICS, PG_checked is cleared in page_alloc.c and only otherwise used in
fs/ext2/dir.c, freexfs/xvfs_subr.c(commented out actually) and
afs/dir.c.
For PG_slab, should I understand 'fairly optional' to mean 'possibly
dangerous' (ie don't use)?
> PG_highmem can go away. (just use page_zone(page)->is_highmem)
> I would dearly like to dump PG_reserved, but I doubt if I'll get onto that.
> (thinks about what happens if you start a direct-io read from a soundcard DMA
> buffer, and munmap/close while that is in progress...)
>
> So. There's not a lot of fat there, but we're not all out of options.
I can still happily do a few dynamically allocated bitmaps if there are
better things the bits can be used for. (The flags are not costly redo
and need to be redone each suspend & resume anyway).
Of course, on top of all of these questions, Pavel might not like my
code anyway so this might be a moot point :>
Anyway, for the moment, I'll proceed on the assumption that there'll be
enough flags, and I can always switch if needs be.
Regards,
Nigel
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This archive was generated by hypermail 2b29 : Sat Feb 15 2003 - 22:00:31 EST