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    SubjectRe: [patch] block layer: kmemcheck fixes
    Nick Piggin wrote:
    >>> Maybe cpus these days have so much store bandwith that doing
    >>> things like the above is OK, but I doubt it :-)
    >> on modern x86 cpus the memset may even be faster if the memory isn't in
    >> cache;
    >> the "explicit" method ends up doing Write Allocate on the cache lines
    >> (so read them from memory) even though they then end up being written
    >> entirely.
    >> With memset the CPU is told that the entire range is set to a new value, and
    >> the WA can be avoided for the whole-cachelines in the range.
    > Don't you have write combining store buffers? Or is it still speculatively
    > issuing the reads even before the whole cacheline is combined?

    x86 memory order model doesn't allow that quite; and you need a "series" of at least 64 bytes
    without any other memory accesses in between even if it would....
    not happening in practice.

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      Last update: 2008-02-08 23:59    [W:0.020 / U:19.116 seconds]
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