lkml.org 
[lkml]   [2006]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Why is wmb() a no-op on x86_64?
From
Date
>>>>> "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?

Cheers,
Jes
-
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/

\
 
 \ /
  Last update: 2006-01-18 18:09    [W:0.040 / U:0.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site