Messages in this thread |  | | Date | Tue, 30 Oct 2001 11:01:31 -0700 | From | Cort Dougan <> | Subject | Re: please revert bogus patch to vmscan.c |
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Actually, they swung the pendelum the other way for the 64-bit chips. The VSID's (MM contexts) are indirectly accessed via a hash-table (with an on chip TLB-style cache called a SLB).
The speedup from using the software table-walk actually came from emulating x86 instead of using the native hash tables. Pretty slick that emulating a 30-year old MMU and improves performance on the PowerPC, eh?
There was an April Fools Microprocessor reports describing a processor that had gone 64-bit and had a "twisted gothic nightmare of twisted logic" based MMU that involved XOR-ing addresses with random numbers. They were unwittingly predicting the future of the PPC MMU.
The nightmares and shakes have never ended for me, either. Sorry about that, man.
} Gods, I hope they have reconsidered that in their 64-bit chips. The 32-bit } hash chains may be ugly, but the architected 32/64-bit MMU stuff is just } so incredibly baroque that it makes any other MMU look positively } beautiful ("Segments? Segments shmegments. Big deal"). } } I still have the occasional nightmares about the IBM block diagrams } "explaining" the PowerPC MMU in their technical documentation. } } There's probably a perfectly valid explanation for them, though (*). } } Linus } } (*) Probably along the lines of the designers being so high on LSD that } they thought it was a really cool idea. That would certainly explain it in } a very logical fashion. } } - } To unsubscribe from this list: send the line "unsubscribe linux-kernel" in } the body of a message to majordomo@vger.kernel.org } More majordomo info at http://vger.kernel.org/majordomo-info.html } Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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