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Date: Tue, 22 May 2018 18:56:41 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	Boaz Harrosh <boazh@netapp.com>, Jeff Moyer <jmoyer@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Rik van Riel <riel@redhat.com>,
	Jan Kara <jack@suse.cz>, Matthew Wilcox <mawilcox@microsoft.com>,
	Amit Golander <Amit.Golander@netapp.com>
Subject: Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU
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On Tue, May 22, 2018 at 04:46:05PM +0000, Christopher Lameter wrote:
> On Tue, 22 May 2018, Dave Hansen wrote:
> 
> > On 05/22/2018 09:05 AM, Boaz Harrosh wrote:
> > > How can we implement "Private memory"?
> >
> > Per-cpu page tables would do it.
> 
> We already have that for percpu subsystem. See alloc_percpu()

x86 doesn't have per-cpu page tables. And the last time I looked, percpu
also didn't, it played games with staggered ranges in the vmalloc space
and used the [FG]S segment offset to make it work.

Doing proper per-cpu pagetables on x86 is possible, but quite involved
and expensive.