Currently, we only bump the inactive LRU of an object when we bind
into the GTT for a page-fault. As the object may be used many times
before its mapping is zapped, we do not mark it as active as
frequently as we should. Userspace should be calling set-to-GTT-domain
before each pointer deference (for synchronous access) and so is a
good place to mark the buffer as active.
Marking the buffer as recently used places it at the end of the
inactive eviction queue, though still before anything with outstanding
rendering. This reduces the likelihood of evicting a buffer that is
going to be used again by the CPU in the near future. This way we can
hopefully avoid to kick out upload buffers right before we use them on
the gpu.
Note that we need to check that the object is not active or pinned,
for otherwise we create havoc on the active/pinned lists, which also
use obj->mm_list.
The active lists are sorted by and evicted in last GPU rendering
order, access by the CPU to a still active buffer therefore does not
affect its eviction ordering. Pinned objects are currently excluded
from eviction, therefore the only list that we need to bump for GTT
access by the CPU is the inactive list.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Added further explanations to the commit message as discussed
on irc.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html
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