Re: [PATCH 0/9] [RFC] fair-lru eviction

["Thomas Hellström" <thomas@shipmail.org>]

Daniel,

Daniel Vetter wrote:
> Hi all,
>
> This patch series implements the fair-lru eviction Chris Wilson already
> posted with a twist. It's essentially the same idea & algorithm.
> Differnences versus his patch:
> - Doesn't do any allocations while scanning.
> - Implemented in drm_mm.c
>
> In other words, this should also be usable by ttm. The idea is simple:
> Scan through the lru, marking objects as evictable until there is a
> large area of memory free/free-able. Then walk through all the scanned
> objects in reverse, checking which ones fall into this hole. Finally
> evicting them.
>
> Comments, ideas highly welcome.
>
> As per usual, I couldn't resist and had to clean up the code in drm_mm.c a
> little.
>
> Yours, Daniel
>
>   

While the cleanup of drm_mm.c looks fine to me, I'm not sure the fair 
eviction is easy to implement with TTM.

TTM releases the spinlock protecting the drm_mm manager in between 
evictions to be able to wait (without holding locks) for bo idle. That 
means that the lru list may have changed between the first eviction and 
the next. In practice, drivers either don't allow simultaneous bo 
validation or should disallow it if thrashing is likely to occur, so the 
likelyhood of the lru list changing in between evictions should be small 
but it needs to be taken into account.

Nevertheless, the drm_mm.c cleanup is
Acked-by: Thomas Hellstrom <thellstrom@vmwgfx.com>

I'll leave it to the Intel guys to comment on the fair eviction stuff.

/Thomas



> Daniel Vetter (9):
>   list.h: add list_for_each_entry_safe_from_reverse
>   drm: use list_for_each_entry in drm_mm.c
>   drm: kill drm_mm_node->private
>   drm: kill dead code in drm_mm.c
>   drm: sane naming for drm_mm.c
>   drm_mm: extract check_free_mm_node
>   drm: implement helper functions for scanning lru list
>   drm/i915: prepare for fair lru eviction
>   drm/i915: implement fair lru eviction
>
>  drivers/gpu/drm/drm_mm.c          |  359 ++++++++++++++++++++++++-------------
>  drivers/gpu/drm/i915/i915_gem.c   |  122 ++++++++-----
>  drivers/gpu/drm/ttm/ttm_bo.c      |    6 -
>  drivers/gpu/drm/ttm/ttm_bo_util.c |    2 -
>  include/drm/drm_mm.h              |   27 +++-
>  include/linux/list.h              |   15 ++
>  6 files changed, 347 insertions(+), 184 deletions(-)
>
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