linux-kernel - RE: [PATCH] mm/hugetlb: reduce arch dependent code about huge_pmd

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F32A6478B@ORSMSX114.amr.corp.intel.com>
Date:	Thu, 23 Apr 2015 22:26:18 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Zhang Zhen <zhenzhang.zhang@...wei.com>
CC:	Linux MM <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"catalin.marinas@....com" <catalin.marinas@....com>,
	"james.hogan@...tec.com" <james.hogan@...tec.com>,
	"ralf@...ux-mips.org" <ralf@...ux-mips.org>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
	"cmetcalf@...hip.com" <cmetcalf@...hip.com>,
	"David Rientjes" <rientjes@...gle.com>,
	"James.Yang@...escale.com" <James.Yang@...escale.com>,
	"aneesh.kumar@...ux.vnet.ibm.com" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: RE: [PATCH] mm/hugetlb: reduce arch dependent code about
 huge_pmd_unshare

> Memory fails me.  Why do some architectures (arm, arm64, x86_64) want
> huge_pmd_[un]share() while other architectures (ia64, tile, mips,
> powerpc, metag, sh, s390) do not?

Potentially laziness/ignorance-of-feature?  It looks like this feature started on x86_64 and then spread
to arm*.

Huge pages are weird on ia64 in that they have to be in a specific range of virtual addresses (region 4).
But I don't see why that would prevent sharing pmd's.

-Tony

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