linux-kernel - Re: [PATCH v2 1/5] pmem, dax: clean up clear

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Message-ID: <20151027173112.GA16605@linux.intel.com>
Date:	Tue, 27 Oct 2015 11:31:12 -0600
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	axboe@...com, jack@...e.cz, akpm@...ux-foundation.org,
	linux-nvdimm@...ts.01.org,
	Dave Hansen <dave.hansen@...ux.intel.com>, david@...morbit.com,
	linux-kernel@...r.kernel.org, willy@...ux.intel.com,
	ross.zwisler@...ux.intel.com, hch@....de
Subject: Re: [PATCH v2 1/5] pmem, dax: clean up clear_pmem()

On Thu, Oct 22, 2015 at 01:10:21PM -0400, Dan Williams wrote:
> Both, __dax_pmd_fault, and clear_pmem() were taking special steps to
> clear memory a page at a time to take advantage of non-temporal
> clear_page() implementations.  However, x86_64 does not use
> non-temporal instructions for clear_page(), and arch_clear_pmem() was
> always incurring the cost of __arch_wb_cache_pmem().
> 
> Clean up the assumption that doing clear_pmem() a page at a time is more
> performant.
> 
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Reported-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
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