Re: [PATCH v4 6/6] arch, x86: pmem api for ensuring durability of persistent memory updates

From: Dan Williams
Date: Wed Jun 17 2015 - 10:54:22 EST

On Wed, Jun 17, 2015 at 4:31 AM, Christoph Hellwig <hch@xxxxxx> wrote:
> This mess with arch_ methods and an ops vecor is almost unreadable.
> What's the problem with having something like:
> pmem_foo()
> {
> if (arch_has_pmem) // or sync_pmem
> arch_pmem_foo();
> generic_pmem_foo();
> }
> This adds a branch at runtime, but that shoudn't really be any slower
> than an indirect call on architectures that matter.

No doubt it's premature optimization, but it bothered me that we'll
end up calling cpuid perhaps multiple times every i/o. If it's just a
readability concern I could wrap it in helpers. Getting it upstream
is my primary concern at this point so I have no strong attachment to
the indirect calls if that's all that is preventing an ack.
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