Messages in this thread | | | Subject | Re: Why is wmb() a no-op on x86_64? | From | Jes Sorensen <> | Date | 18 Jan 2006 12:06:39 -0500 |
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>>>>> "Bryan" == Bryan O'Sullivan <bos@pathscale.com> writes:
Bryan> On Wed, 2006-01-18 at 17:29 +0100, Andi Kleen wrote: >> Why do you need the barrier?
Bryan> On x86_64, we fiddle with the MTRRs to enable write combining, Bryan> which makes a huge difference to performance. It's not clear Bryan> to me what we should even do on other architectures, since the Bryan> only generic entry point that even exposes write combining is Bryan> pci_mmap_page_range, which is for PCI mmap through userspace, Bryan> and half the arches I've looked at ignore its write_combine Bryan> parameter.
A job for mmiowb() perhaps?
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