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

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Date:   Thu, 1 Nov 2018 20:06:12 +0800
From:   Vovo Yang <vovoy@...omium.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     owner-linux-mm@...ck.org, 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 Wed, Oct 31, 2018 at 10:19 PM Dave Hansen <dave.hansen@...el.com> wrote:
> On 10/31/18 1:19 AM, owner-linux-mm@...ck.org 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.
>
> 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.