From b7844d12487dbac702ecd734faeffa6fe1a61a83 Mon Sep 17 00:00:00 2001 From: Kenneth Graunke Date: Tue, 30 Sep 2014 01:15:56 -0700 Subject: [PATCH] i965: Use BDW_MOCS_PTE for renderbuffers. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Write-back caching cannot be used for buffers being scanned out by the display engine; surfaces used for scan-out must be write-through or uncached. I originally chose WT for render targets because it works in all cases. However, we really want to use write-back caching where possible, as it is more efficient. Most renderbuffers are not used for scanout - off-screen FBOs certainly are fine, and non-pageflipped backbuffers should be fine as well. So in most cases WB will work. However, we don't know what will be used for scan-out, so we instead simply use the PTE value specified by the kernel, as it knows these things. This matches our MOCS choice on Haswell. Fixes performance regressions since commit ee4484be3dc827cf15bcf109f5 in a microbenchmark (spotted by Eero Tamminen). Improves performance in GLBenchmark 2.7/EgyptHD by 7.44362% +/- 0.496939% (n=55) on a Broadwell GT2. Improves performance in a bunch of other microbenchmarks by ~15% or so. Signed-off-by: Kenneth Graunke Reported-by: Eero Tamminen Reviewed-by: Daniel Vetter Reviewed-by: Kristian Høgsberg Cc: mesa-stable@lists.freedesktop.org --- src/mesa/drivers/dri/i965/gen8_surface_state.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/mesa/drivers/dri/i965/gen8_surface_state.c b/src/mesa/drivers/dri/i965/gen8_surface_state.c index 40eb2eab0ae..6dd343f57f4 100644 --- a/src/mesa/drivers/dri/i965/gen8_surface_state.c +++ b/src/mesa/drivers/dri/i965/gen8_surface_state.c @@ -377,7 +377,7 @@ gen8_update_renderbuffer_surface(struct brw_context *brw, horizontal_alignment(mt) | surface_tiling_mode(tiling); - surf[1] = SET_FIELD(BDW_MOCS_WT, GEN8_SURFACE_MOCS) | mt->qpitch >> 2; + surf[1] = SET_FIELD(BDW_MOCS_PTE, GEN8_SURFACE_MOCS) | mt->qpitch >> 2; surf[2] = SET_FIELD(width - 1, GEN7_SURFACE_WIDTH) | SET_FIELD(height - 1, GEN7_SURFACE_HEIGHT); -- 2.30.2