linux-kernel - Re: [RFC 0/2] kvm: Transcendent Memory (tmem) on KVM

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Message-ID: <4F6230B1.4010004@redhat.com>
Date:	Thu, 15 Mar 2012 20:10:57 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Akshay Karle <akshay.a.karle@...il.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	ashu tripathi <er.ashutripathi@...il.com>,
	nishant gulhane <nishant.s.gulhane@...il.com>,
	amarmore2006 <amarmore2006@...il.com>,
	Shreyas Mahure <shreyas.mahure@...il.com>,
	mahesh mohan <mahesh6490@...il.com>
Subject: Re: [RFC 0/2] kvm: Transcendent Memory (tmem) on KVM

On 03/15/2012 08:02 PM, Konrad Rzeszutek Wilk wrote:
> > 
> > Nice.  This takes care of the tail-end of the streaming (the more
> > important one - since it always involves a cold copy).  What about the
> > other side?  Won't the read code invoke cleancache_get_page() for every
> > page? (this one is just a null hypercall, so it's cheaper, but still
> > expensive).
>
> That is something we should fix - I think it was mentioned in the frontswap
> email thread the need for batching and it certainly seems required as those
> hypercalls aren't that cheap.

In fact when tmem was first proposed I asked for two changes - make it
batchable, and make it asynchronous (so we can offload copies to a dma
engine, etc).  Of course that would have made tmem significantly more
complicated.

-- 
error compiling committee.c: too many arguments to function

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