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Date: Wed, 18 Oct 2017 18:10:56 -0700 From: Matthew Wilcox <willy@...radead.org> To: Andi Kleen <ak@...ux.intel.com> Cc: Srividya Desireddy <srividya.dr@...sung.com>, "sjenning@...hat.com" <sjenning@...hat.com>, "ddstreet@...e.org" <ddstreet@...e.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "penberg@...nel.org" <penberg@...nel.org>, Dinakar Reddy Pathireddy <dinakar.p@...sung.com>, SHARAN ALLUR <sharan.allur@...sung.com>, RAJIB BASU <rajib.basu@...sung.com>, JUHUN KIM <juhunkim@...sung.com>, "srividya.desireddy@...il.com" <srividya.desireddy@...il.com> Subject: Re: [PATCH] zswap: Same-filled pages handling 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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