linux-kernel - Re: [PATCH 3/6] x86, pmem: add PMEM API for persistent memory

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Date:	Thu, 28 May 2015 21:19:01 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dan Williams <dan.j.williams@...el.com>
CC:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH 3/6] x86, pmem: add PMEM API for persistent memory

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.

	-hpa

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