https://github.com/torvalds/linux
Revision 0e6d6ec02f867fe8d1f785312b7343b21052322f authored by Thomas Hellstrom on 12 March 2014, 09:41:32 UTC, committed by Thomas Hellstrom on 12 March 2014, 13:07:24 UTC
A performance regression was introduced in TTM in linux 3.13 when we started using
VM_PFNMAP for shared mappings. In theory this should've been faster due to
less page book-keeping but it appears like VM_PFNMAP + x86 PAT + write-combine
is a particularly cpu-hungry combination, as seen by largely increased
cpu-usage on r200 GL video playback.

Until we've sorted out why, revert to always use VM_MIXEDMAP.
Reference: freedesktop.org bugzilla bug #75719

Reported-and-tested-by: <smoki00790@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Cc: stable@vger.kernel.org
1 parent 45db98e
History
Tip revision: 0e6d6ec02f867fe8d1f785312b7343b21052322f authored by Thomas Hellstrom on 12 March 2014, 09:41:32 UTC
drm/ttm: Work around performance regression with VM_PFNMAP
Tip revision: 0e6d6ec
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