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Date: Thu, 19 Oct 2017 06:24:27 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] zswap: Same-filled pages handling
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To: Andi Kleen <ak@linux.intel.com>
Cc: Srividya Desireddy <srividya.dr@samsung.com>, "sjenning@redhat.com" <sjenning@redhat.com>, "ddstreet@ieee.org" <ddstreet@ieee.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "penberg@kernel.org" <penberg@kernel.org>, Dinakar Reddy Pathireddy <dinakar.p@samsung.com>, SHARAN ALLUR <sharan.allur@samsung.com>, RAJIB BASU <rajib.basu@samsung.com>, JUHUN KIM <juhunkim@samsung.com>, "srividya.desireddy@gmail.com" <srividya.desireddy@gmail.com>

On Wed, Oct 18, 2017 at 09:30:32PM -0700, Andi Kleen wrote:
> > Yes.  Every 64-bit repeating pattern is also a 32-bit repeating pattern.
> > Supporting a 64-bit pattern on a 32-bit kernel is painful, but it makes
> > no sense to *not* support a 64-bit pattern on a 64-bit kernel.  
> 
> But a 32bit repeating pattern is not necessarily a 64bit pattern.

Oops, I said it backwards.  What I mean is that if you have the repeating
pattern:

0x12345678 12345678 12345678 12345678 12345678 12345678

that's the same as the repeating pattern:

0x1234567812345678 1234567812345678 1234567812345678

so the 64-bit kernel is able to find all patterns that the 32-bit kernel is,
and more.

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