linux-kernel - Re: [PATCH v3] mm, drm/i915: mark pinned shmemfs pages as unevictable

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Date:   Thu, 1 Nov 2018 07:30:30 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Vovo Yang <vovoy@...omium.org>
Cc:     linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        linux-mm@...ck.org, Chris Wilson <chris@...is-wilson.co.uk>,
        Michal Hocko <mhocko@...e.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3] mm, drm/i915: mark pinned shmemfs pages as unevictable

On 11/1/18 5:06 AM, Vovo Yang wrote:
>> mlock() and ramfs usage are pretty easy to track down.  /proc/$pid/smaps
>> or /proc/meminfo can show us mlock() and good ol' 'df' and friends can
>> show us ramfs the extent of pinned memory.
>>
>> With these, if we see "Unevictable" in meminfo bump up, we at least have
>> a starting point to find the cause.
>>
>> Do we have an equivalent for i915?
> AFAIK, there is no way to get i915 unevictable page count, some
> modification to i915 debugfs is required.

Is something like this feasible to add to this patch set before it gets
merged?  For now, it's probably easy to tell if i915 is at fault because
if the unevictable memory isn't from mlock or ramfs, it must be i915.

But, if we leave it as-is, it'll just defer the issue to the fourth user
of the unevictable list, who will have to come back and add some
debugging for this.

Seems prudent to just do it now.