Hi all, drm/i915 has write/read paths to upload/download data to/from gpu buffer objects. For a bunch of reasons we have special fastpaths with decent setup costs, so when we fall back to the slow-path we don't fully recover to the fastest fast-path when grabbing our locks again. This is also in parts due to that we have multiple fallbacks to slower paths, so control-flow in our code would get really ugly. As part of a larger rewrite and re-tuning of these functions we've noticed that the prefault helpers in pagemap.h only prefault up to PAGE_SIZE because that's all the other users need. The follow-up patch extends this to abritary sizes so that we can fully exploit our special fastpaths in more cases (we typically see reads and writes of a few pages up to a few mb). I'd like to get this in for 3.4. There's no functional dependency between this patch and the drm/i915 rework (only performance effects), so this can go in through -mm without causing merge issues. If this or something similar isn't acceptable, plan B is to hand-roll these 2 functions in drm/i915. But I don't like nih these things in driver code much. Comments highly welcome. Yours, Daniel For reference, the drm/i915 read/write rework is avaialable at: http://cgit.freedesktop.org/~danvet/drm/log/?h=pwrite-pread Unfortunately cgit.fd.o is currently on hiatus. Daniel Vetter (1): mm: extend prefault helpers to fault in more than PAGE_SIZE include/linux/pagemap.h | 28 ++++++++++++++++++---------- 1 files changed, 18 insertions(+), 10 deletions(-) -- 1.7.7.5
