From: Ian Romanick <idr@freedesktop.org>
To: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: Trying to understand the URB code
Date: Fri, 08 Apr 2011 12:03:34 -0700 [thread overview]
Message-ID: <4D9F5C06.3050003@freedesktop.org> (raw)
In-Reply-To: <41EFD7A46E18724CAB128DAD007334801A38271840@shsmsx502.ccr.corp.intel.com>
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On 04/07/2011 01:24 AM, Zou, Nanhai wrote:
> Hi Ken,
> URB allocation on gen6 is different than previous gens.
> On previous gen, there is a total size urb for many stages of VS GS CLIP SF.
> So driver has to decide how much urb to allocate for each stage.
>
> On gen6 only GS and VS will share an urb of 64k(32k on GT1)
>
> urb_entry_number also has a limit, check 3DSTATE_URB command.
Ken and I did some research on this yesterday. The bspec says the valid
range for the VS is [24, 256] on GT2 and [24, 128] on GT1. For the GS
it says the valid range is [0, 256] on GT2 and [0, 254] on GT1. I can't
believe that 254 is correct.
> The more urb entry number we have, the more current threads can spawn.
>
> But
> We should make sure
> VS urb size = single_urb_size * gs_urb_entry
> +
> GS urb size = single_urb_size * vs_urb_entry
> < total_urb_size
>
> In most case, this is ok, unless we have a huge single_urb_size.
>
> Since we are always using GS pass through mode for now.
> The number for GS urb dose not matter.
> So allocate more urb size for VS, less for GS may be better for huge urb_size
>
> But consider we will support GS shader later and huge urb_size case is very rare,
> I separate urb equally for GS and VS.
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prev parent reply other threads:[~2011-04-08 19:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-07 5:01 Trying to understand the URB code Kenneth Graunke
2011-04-07 8:24 ` Zou, Nanhai
2011-04-08 19:03 ` Ian Romanick [this message]
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