Messages in this thread | | | Date | Tue, 10 Jan 2006 12:30:43 -0700 | From | "Jeff V. Merkey" <> | Subject | Re: 2G memory split |
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Jens Axboe wrote:
>On Tue, Jan 10 2006, Jeff V. Merkey wrote: > > >>Alan Cox wrote: >> >> >> >>>On Maw, 2006-01-10 at 09:56 -0700, Jeff V. Merkey wrote: >>> >>> >>> >>> >>>>RH ES uses 4:4 which is ideal and superior to this hack. >>>> >>>> >>>> >>>> >>>Its a non trivial trade-off. 4/4 lets you run very large physical memory >>>systems much more efficiently than usual but you pay a cost on syscalls >>>and some other events when using the majority of processors. The 4/4 >>>tricks also give most emulations (eg Qemu) serious heartburn trying to >>>emulate %cr3 reloading via mmap and other interfaces with high overhead >>>in relative terms. >>> >>>Of course AMD64 kind of shot the problem in the head once and for all. >>> >>> >>> >>> >>> >>Yep, they sure did. Seriously, the 4:4 option should also be present >>along with 3:1 and 2:2 >>splits. You should merge your RH work into this patch and allow both. >>It would save me one less >>patch to maintain off the tree. >> >> > >You can't compare the two patches, saying that 4:4 should go in because >configurable page offsets is merged is nonsense. > >Note that I'm not advocating against 4:4 as such, I have no real >oppinion on that. It has its uses for sure, while it comes with a cost >for others. > > > I agree and I appreciate your recognizing this. As it stands, if I need 4:4 I just ship on ES3 and ES4. the 3:1 patch in the standard kernel is a very good thing, and you are to be commended for finally getting it in.
P.S. Your bio stuff works great.
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