Re: [PATCH v2 2/3] x86: drop a comment left over from X86_OOSTORE

[PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-12
[PATCH v2 1/3] x86: drop mfence in favor of lock+addl · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-12
[PATCH v2 3/3] x86: tweak the comment about use of wmb for IO · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-12
[PATCH v2 2/3] x86: drop a comment left over from X86_OOSTORE · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-12
Re: [PATCH v2 2/3] x86: drop a comment left over from X86_OOSTORE · One Thousand Gnomes <hidden> · 2016-01-12
Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · "H. Peter Anvin" <hpa@zytor.com> · 2016-01-12
Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-26
Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · "H. Peter Anvin" <hpa@zytor.com> · 2016-01-26
Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-27
Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · Peter Zijlstra <peterz@infradead.org> · 2016-01-27
Re: [PATCH v2 0/3] x86: faster mb()+other barrier.h tweaks · "Michael S. Tsirkin" <mst@redhat.com> · 2016-01-27

From: One Thousand Gnomes <hidden>
Date: 2016-01-12 22:25:28

On Wed, 13 Jan 2016 00:10:19 +0200
"Michael S. Tsirkin" [off-list ref] wrote:

The comment about wmb being non-nop is a left over from before commit
09df7c4c8097 ("x86: Remove CONFIG_X86_OOSTORE").

It makes no sense now: if you have an SMP system with out of order
stores, making wmb not a nop will not help.

There were never any IDT Winchip systems with SMP support, and they were
the one system that could enable OOSTORE (and it was worth up to 30% on
some workloads). The fencing it had was just for DMA devices.

Alan

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