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Date: Thu, 1 Jun 2017 18:35:18 -0400 From: Jerome Glisse <jglisse@...hat.com> To: Balbir Singh <bsingharora@...il.com> Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Dan Williams <dan.j.williams@...el.com>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, John Hubbard <jhubbard@...dia.com>, Evgeny Baskakov <ebaskakov@...dia.com>, Mark Hairgrove <mhairgrove@...dia.com>, Sherry Cheung <SCheung@...dia.com>, Subhash Gutti <sgutti@...dia.com> Subject: Re: [HMM 12/15] mm/migrate: new memory migration helper for use with device memory v4 On Wed, May 31, 2017 at 01:59:54PM +1000, Balbir Singh wrote: > On Wed, 24 May 2017 13:20:21 -0400 > Jérôme Glisse <jglisse@...hat.com> wrote: > > > This patch add a new memory migration helpers, which migrate memory > > backing a range of virtual address of a process to different memory > > (which can be allocated through special allocator). It differs from > > numa migration by working on a range of virtual address and thus by > > doing migration in chunk that can be large enough to use DMA engine > > or special copy offloading engine. > > > > Expected users are any one with heterogeneous memory where different > > memory have different characteristics (latency, bandwidth, ...). As > > an example IBM platform with CAPI bus can make use of this feature > > to migrate between regular memory and CAPI device memory. New CPU > > architecture with a pool of high performance memory not manage as > > cache but presented as regular memory (while being faster and with > > lower latency than DDR) will also be prime user of this patch. > > > > Migration to private device memory will be useful for device that > > have large pool of such like GPU, NVidia plans to use HMM for that. > > > > It is helpful, for HMM-CDM however we would like to avoid the downsides > of MIGRATE_SYNC_NOCOPY What are the downside you are referring too ? Cheers, Jérôme
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