Re: Support for amdgpu VM update via CPU on large-bar systems

From: zhoucm1 <david1.zhou-5C7GfCeVMHo@public.gmane.org>
To: "Kasiviswanathan,
	Harish" <Harish.Kasiviswanathan-5C7GfCeVMHo@public.gmane.org>,
	"amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
	<amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>
Subject: Re: Support for amdgpu VM update via CPU on large-bar systems
Date: Fri, 12 May 2017 16:25:30 +0800	[thread overview]
Message-ID: <5915717A.3000209@amd.com> (raw)
In-Reply-To: <DM3PR1201MB10382F282D646D630708246D8CEF0-BBcFnVpqZhWjUUTFdQAMQmrFom/aUZj6nBOFsp37pqbUKgpGm//BTAC/G2K4zDHf@public.gmane.org>


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On 2017年05月10日 05:47, Kasiviswanathan, Harish wrote:
> Hi,
>
> Please review the patch set that supports amdgpu VM update via CPU. This feature provides improved performance for compute (HSA) where mapping / unmapping is carried out (by Kernel) independent of command submissions (done directly by user space). This version doesn't support shadow copy of VM page tables for CPU based update.
I think your improved performance is from less waiting for cs, 
generally, SDMA engine updating page table is faster than CPU, otherwise 
we don't need sdma for updating PT.
So whether your this improvement proves we have some redundant sync when 
mapping / unmapping, if yes, we should fix that, then not sure if CPU 
method is need or not.

Regards,
David Zhou
>
> Best Regards,
> Harish
>
>
>
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