Re: 4.7 vs 5.2.1 SMP/UP bridging performance

From: Robert Watson (rwatson_at_FreeBSD.org)
Date: 05/07/04

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    Date: Thu, 6 May 2004 22:55:46 -0400 (EDT)
To: John Baldwin <jhb@FreeBSD.org>

    On Thu, 6 May 2004, John Baldwin wrote:

    > > According to http://www.sandpile.org/ia32/coherent.htm,
    > > both mfence and lfence require SSE2, so sfence has the broadest
    > > coverage.
    > >
    > > But since only P4 needs it, and since lfence is ~25% cheaper, maybe
    > > there should be a separate config option for it, and it should be a
    > > straight conditional compile option for those of us cursed w/P4s.
    >
    > That could work I guess. Just can't stick it in GENERIC.
    >
    > options INTEL_MADE_MY_PIV_A_TORTOISE
    >
    > or some such. :)

    On occasion, I've had conversations with Peter Wemm about providing HAL
    modules with optimized versions of various common routines for specific
    hardware platforms. However, that would require us to make a trade-off
    between the performance benefits of inlining and the performance benefits
    of a HAL module...

    Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
    robert@fledge.watson.org Senior Research Scientist, McAfee Research

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