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From: Matthew Wilcox <willy@infradead.org>
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>
Subject: Re: [PATCH] zswap: Same-filled pages handling
Date: Wed, 18 Oct 2017 18:10:56 -0700
Message-ID: <20171019011056.GB17308@bombadil.infradead.org> (raw)
In-Reply-To: <8760bci3vl.fsf@linux.intel.com>

On Wed, Oct 18, 2017 at 01:43:10PM -0700, Andi Kleen wrote:
> > +static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
> > +{
> > +	unsigned int pos;
> > +	unsigned long *page;
> > +
> > +	page = (unsigned long *)ptr;
> > +	for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
> > +		if (page[pos] != page[0])
> > +			return 0;
> > +	}
> 
> So on 32bit it checks for 32bit repeating values and on 64bit
> for 64bit repeating values. Does that make sense?

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.  This is
the same approach used in zram, fwiw.

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Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1>
2017-10-18 10:48 ` Srividya Desireddy
2017-10-18 12:34   ` Matthew Wilcox
2017-10-18 13:33     ` Timofey Titovets
2017-10-18 14:11       ` Matthew Wilcox
2017-10-18 20:43   ` Andi Kleen
2017-10-19  1:10     ` Matthew Wilcox [this message]
2017-10-19  4:30       ` Andi Kleen
2017-10-19 13:24         ` Matthew Wilcox
2017-10-18 21:31   ` Timofey Titovets
2017-10-19  1:08     ` Matthew Wilcox
     [not found]     ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p3>
2017-11-02 15:08       ` Srividya Desireddy
2017-11-17 22:10         ` Dan Streetman
2017-11-17 22:07     ` Dan Streetman
2017-11-17 21:27   ` Dan Streetman
2017-11-20 23:46   ` Andrew Morton
2017-11-28 11:35     ` Dan Streetman
     [not found]     ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p6>
2017-11-29 15:34       ` [PATCH] zswap: Update with same-value filled page feature Srividya Desireddy
2017-11-29 21:29         ` Dan Streetman
2017-12-06 11:48       ` [PATCH v2] " Srividya Desireddy
2017-12-06 15:20         ` Dan Streetman
     [not found]   ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p4>
2017-11-21 14:18     ` [PATCH v2] zswap: Same-filled pages handling Srividya Desireddy
2017-10-18 14:43 ` [PATCH] " Srividya Desireddy

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