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Subject: Re: [PATCH v4] mm, drm/i915: mark pinned shmemfs pages as unevictable
References: <20181105111348.182492-1-vovoy@chromium.org>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <516428f4-93a9-9ed7-426e-344ba91d81e0@intel.com>
Date: Mon, 5 Nov 2018 10:52:34 -0800
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Sender: owner-linux-mm@kvack.org
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To: Kuo-Hsin Yang <vovoy@chromium.org>, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>, Michal Hocko <mhocko@suse.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Peter Zijlstra <peterz@infradead.org>, Andrew Morton <akpm@linux-foundation.org>

On 11/5/18 3:13 AM, Kuo-Hsin Yang wrote:
> -These are currently used in two places in the kernel:
> +These are currently used in three places in the kernel:
>  
>   (1) By ramfs to mark the address spaces of its inodes when they are created,
>       and this mark remains for the life of the inode.
> @@ -154,6 +154,8 @@ These are currently used in two places in the kernel:
>       swapped out; the application must touch the pages manually if it wants to
>       ensure they're in memory.
>  
> + (3) By the i915 driver to mark pinned address space until it's unpinned.

At a minimum, I think we owe some documentation here of how to tell
approximately how much memory i915 is consuming with this mechanism.
The debugfs stuff sounds like a halfway reasonable way to approximate
it, although it's imperfect.