linux-kernel - Re: [PATCH 2/2] drm/i915: Mark pinned shmemfs pages as unevictable

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Date:   Tue, 16 Oct 2018 20:21:55 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Kuo-Hsin Yang <vovoy@...omium.org>
Cc:     linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        chris@...is-wilson.co.uk, peterz@...radead.org,
        dave.hansen@...el.com, corbet@....net, hughd@...gle.com,
        joonas.lahtinen@...ux.intel.com, marcheu@...omium.org,
        hoegsberg@...omium.org
Subject: Re: [PATCH 2/2] drm/i915: Mark pinned shmemfs pages as unevictable

On Wed 17-10-18 01:43:00, Kuo-Hsin Yang wrote:
> The i915 driver use shmemfs to allocate backing storage for gem objects.
> These shmemfs pages can be pinned (increased ref count) by
> shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
> wastes a lot of time scanning these pinned pages. Mark these pinned
> pages as unevictable to speed up vmscan.

I would squash the two patches into the single one. One more thing
though. One more thing to be careful about here. Unless I miss something
such a page is not migrateable so it shouldn't be allocated from a
movable zone. Does mapping_gfp_constraint contains __GFP_MOVABLE? If
yes, we want to drop it as well. Other than that the patch makes sense
with my very limited knowlege of the i915 code of course.
-- 
Michal Hocko
SUSE Labs