Messages in this thread | | | Date | Thu, 08 Apr 2004 16:42:37 -0700 | From | "Martin J. Bligh" <> | Subject | Re: -mmX 4G patches feedback [numbers: how much performance impact] |
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--On Friday, April 09, 2004 01:22:15 +0200 Andrea Arcangeli <andrea@suse.de> wrote:
> On Thu, Apr 08, 2004 at 04:14:08PM -0700, Martin J. Bligh wrote: >> Me confused. Are you saying it's worse compared to pte_highmem? or to >> shoving ptes in lowmem? > > worse than pte_highmem if booting with mem=800m > >> Ah. You're worried about the distro situation, where PTE_HIGHMEM would >> be turned on for a non-highmem machine, right? Makes more sense I guess. > > it's not just a distro situation, it's about not having to recompile the > kernel for every machine I own, even gentoo has an option to have a > compile server in the network that build packages and you install the > binaries from it, so there must be some value in being able to share a > binary on more than one machine (this is especially true for me since I > upgrade kernel quite fast). > > it's not just about non-highmem machines, on 1G/2G boxes the probability > that pte-highmem cause you any slowdown is an order of magnitude smaller > than on a 32G machine (where ptes should never hit lowmem or it means my > classzone lowmem_reserve_ratio algorithms have not yet been ported to 2.6) > with your model you'd have no way to boost when you are lucky to get a > lowmem page.
OK, I think I understand your concern now - I was being slow ;-) I guess there are a few more PTEs to set up on exec, you're right. I still think it's faster than pte_highmem, which was a static config option anyway (so it's better in all cases than pte_highmem, when enabled) but still not perfect. Hmm. I'll go think about it ;-)
m.
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