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    SubjectRe: [PATCH 3/6] x86, pmem: add PMEM API for persistent memory
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    On Thu, 2015-05-28 at 21:19 -0700, H. Peter Anvin wrote:
    > On 05/28/2015 05:02 PM, Dan Williams wrote:
    > >
    > > Hmm, yes, but I believe Ross (on vacation now) was following the
    > > precedent set by commit cd8ddf1a2800 "x86: clflush_page_range needs
    > > mfence" whereby the api handles all necessary fencing internally.
    > > Shall we introduce something like __unordered_clflush_cache_range()
    > > for arch_persistent_flush() to use with the understanding it will
    > > be
    > > following up with the wmb() in arch_persistent_sync()?
    > >
    >
    > Are we ever going to have arch_persistent_sync() without
    > arch_persistent_flush()?
    >
    > However, thinking about it, it would be more efficient to do all
    > flushes
    > first and then have a single barrier.

    Yep, we have arch_persistent_sync() without arch_persistent_flush() in
    both our PMEM and ND_BLK write paths. These use arch_persistent_copy() to get NT stores, so they don't need to manually flush/write-back
    before doing a persistent_sync().


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