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From: "Wang, Zhi A" <zhi.a.wang@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"intel-gvt-dev@lists.freedesktop.org"
	<intel-gvt-dev@lists.freedesktop.org>
Cc: "Vivi, Rodrigo" <rodrigo.vivi@intel.com>,
	"Widawsky, Benjamin" <benjamin.widawsky@intel.com>
Subject: Re: [RFCv5 2/2] drm/i915: Introduce private PAT management
Date: Tue, 29 Aug 2017 18:19:14 +0000	[thread overview]
Message-ID: <F3B0350DF4CB6849A642218320DE483D7D603D0E@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <150403044958.916.16058791940672260372@mail.alporthouse.com>

I see. 

For 1) I can fix it in the next RFC.
For 2) I can find some VPG guys to ask for the details.

Thanks,
Zhi.

-----Original Message-----
From: Chris Wilson [mailto:chris@chris-wilson.co.uk] 
Sent: Tuesday, August 29, 2017 9:14 PM
To: Wang, Zhi A <zhi.a.wang@intel.com>; Joonas Lahtinen <joonas.lahtinen@linux.intel.com>; intel-gfx@lists.freedesktop.org; intel-gvt-dev@lists.freedesktop.org
Cc: zhenyuw@linux.intel.com; Widawsky, Benjamin <benjamin.widawsky@intel.com>; Vivi, Rodrigo <rodrigo.vivi@intel.com>
Subject: RE: [RFCv5 2/2] drm/i915: Introduce private PAT management

Quoting Wang, Zhi A (2017-08-29 18:54:51)
> Another finding during the re-factoring are:
> 
> a)It looks like that the PPAT_CACHE_INDEX on BDW/SKL is mapped to:
> GEN8_PPAT_WB | GEN8_PPAT_LLCELLC | GEN8_PPAT_AGE(0);
> 
> But the PPAT_CACHE_INDEX on CNL is mapped to GEN8_PPAT_LLCELLC | 
> GEN8_PPAT_AGE(0);
> 
> GEN8_PPAT_WB is missing here and by default the cache attribute is UC.
> 
> Is this set intentionally?

That sounds like a nasty little bug.

> b) Looks like all the ages of PPAT in windows driver is AGE(3) because of some performance gains, is there any reason that i915 has to set it to AGE(0)?

Nope, it's never been rigorously tested. On occasion, we've swapped it around (at least for the older gen) and never found a significant difference; I haven't even heard if anyone has tried such experiments on gen8+. Off the top of my head, the age should only matter when you have PTE with different ages (unless there's some automatic clock algorithm tracking the age on each page in a shadow, the challenge being then when you decide to refresh the age from the PTE.) -Chris
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  reply	other threads:[~2017-08-29 18:19 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-29  8:00 [RFCv5 1/2] drm/i915: Factor out setup_private_pat() Zhi Wang
2017-08-29  8:00 ` [RFCv5 2/2] drm/i915: Introduce private PAT management Zhi Wang
2017-08-29  9:37   ` Joonas Lahtinen
2017-08-29 11:18     ` Wang, Zhi A
2017-08-29 17:54     ` Wang, Zhi A
2017-08-29 18:14       ` Chris Wilson
2017-08-29 18:19         ` Wang, Zhi A [this message]
2017-08-30 11:09           ` Joonas Lahtinen
2017-08-29 10:05   ` Chris Wilson
2017-08-29 10:39     ` Chris Wilson
2017-08-29 11:13       ` Wang, Zhi A
2017-08-29 11:23         ` Chris Wilson
2017-08-29 11:31           ` Wang, Zhi A
2017-08-29 11:38           ` Joonas Lahtinen
2017-08-29 12:12   ` Chris Wilson
2017-08-29 12:18   ` Chris Wilson
2017-08-29 12:41     ` Wang, Zhi A
2017-08-29  8:19 ` ✓ Fi.CI.BAT: success for series starting with [RFCv5,1/2] drm/i915: Factor out setup_private_pat() Patchwork
2017-08-29  9:39 ` ✗ Fi.CI.IGT: failure " Patchwork

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