linux-kernel - Re: [PATCH 08/10] drm/tegra: Implement dynamic channel allocation model

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Message-ID: <38fcf947-0d5d-e2c7-f49f-9efce5eeb1a3@kapsi.fi>
Date:   Tue, 7 Nov 2017 14:29:52 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Dmitry Osipenko <digetx@...il.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] drm/tegra: Implement dynamic channel allocation
 model

On 05.11.2017 19:43, Dmitry Osipenko wrote:
> On 05.11.2017 14:01, Mikko Perttunen wrote:
>> In the traditional channel allocation model, a single hardware channel
>> was allocated for each client. This is simple from an implementation
>> perspective but prevents use of hardware scheduling.
>>
>> This patch implements a channel allocation model where when a user
>> submits a job for a context, a hardware channel is allocated for
>> that context. The same channel is kept for as long as there are
>> incomplete jobs for that context. This way we can use hardware
>> scheduling and channel isolation between userspace processes, but
>> also prevent idling contexts from taking up hardware resources.
>>
>
> The dynamic channels resources (pushbuf) allocation is very expensive,
> neglecting all benefits that this model should bring at least in non-IOMMU case.
> We could have statically preallocated channels resources or defer resources freeing.

This is true. I'll try to figure out a nice way to keep the pushbuf 
allocations.

>
>> For now, this patch only adapts VIC to the new model.
>>
>
> I think VIC's conversion should be a distinct patch.

Sure.

Cheers,
Mikko