Re: [patch] SMP alternatives

From: H. Peter Anvin
Date: Wed Nov 23 2005 - 17:22:58 EST

Alan Cox wrote:
On Mer, 2005-11-23 at 13:36 -0800, Linus Torvalds wrote:

have to add PAT support which we need to do anyway we would get a world
where on uniprocessor lock prefix only works on addresse targets we want
it to - ie pci_alloc_consistent() pages.

No. That would be wrong.

The thing is, "lock" is useless EVEN ON SMP in user space 99% of the time.

Now I see what you are aiming at, yes that makes vast amounts of sense
and since AMD have the "no lock effect" bit for general case maybe they

What it really comes down to (virtualization or not!) is whether or not the OS can guarantee that nothing else is messing with memory at the same time.

This is potentially different from process to process (because of page table differences) and from kernel to user space (because of the User bit in the page tables.)


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