On Fri, Nov 22, 2013 at 09:53:23AM -0800, Jesse Barnes wrote: > On Fri, 22 Nov 2013 10:37:53 +0000 > Chris Wilson <ch...@chris-wilson.co.uk> wrote: > > > We have conflicting benchmark data that suggest either age 0 or age 3 is > > better. However, the earlier benchmark on which we based the switch to > > age 0 > > > > (commit 0d8ff15e9a15f2b393e53337a107b7a1e5919b6d > > Author: Ben Widawsky <benjamin.widaw...@intel.com> > > Date: Thu Jul 4 11:02:03 2013 -0700 > > > > drm/i915/hsw: Set correct Haswell PTE encodings) > > > > actually seems to prefer the default PTE encoding as age 3. Presumably, > > this is in part due to the use of MOCS to override the PTE encodings > > when appropriate. > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=69870 > > Tested-by: mengmeng.m...@intel.com > > Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> > > --- > > drivers/gpu/drm/i915/i915_gem_gtt.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c > > b/drivers/gpu/drm/i915/i915_gem_gtt.c > > index efb5dab61c81..c4a3f9ae0d43 100644 > > --- a/drivers/gpu/drm/i915/i915_gem_gtt.c > > +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c > > @@ -57,7 +57,9 @@ typedef gen8_gtt_pte_t gen8_ppgtt_pde_t; > > #define HSW_WB_LLC_AGE3 HSW_CACHEABILITY_CONTROL(0x2) > > #define HSW_WB_LLC_AGE0 HSW_CACHEABILITY_CONTROL(0x3) > > #define HSW_WB_ELLC_LLC_AGE0 HSW_CACHEABILITY_CONTROL(0xb) > > +#define HSW_WB_ELLC_LLC_AGE3 HSW_CACHEABILITY_CONTROL(0x8) > > #define HSW_WT_ELLC_LLC_AGE0 HSW_CACHEABILITY_CONTROL(0x6) > > +#define HSW_WT_ELLC_LLC_AGE3 HSW_CACHEABILITY_CONTROL(0x7) > > > > #define GEN8_PTES_PER_PAGE (PAGE_SIZE / sizeof(gen8_gtt_pte_t)) > > #define GEN8_PDES_PER_PAGE (PAGE_SIZE / sizeof(gen8_ppgtt_pde_t)) > > @@ -185,10 +187,10 @@ static gen6_gtt_pte_t iris_pte_encode(dma_addr_t addr, > > case I915_CACHE_NONE: > > break; > > case I915_CACHE_WT: > > - pte |= HSW_WT_ELLC_LLC_AGE0; > > + pte |= HSW_WT_ELLC_LLC_AGE3; > > break; > > default: > > - pte |= HSW_WB_ELLC_LLC_AGE0; > > + pte |= HSW_WB_ELLC_LLC_AGE3; > > break; > > } > > > > Yeah I guess as long as userspace can override the default with MOCS, > this is fine.
IIRC MOCS can only set the age to 3. So this change does limit what userspace might achieve w/ MOCS usage a little bit. I guess it might be better to change userspace to set everything to LLC(+eLLC) at age 3 via MOCS (except potential scanout buffers), and leave the PTE default at age 0. But then again we need to also remember that not everything has a MOCS field. So I'm not sure there's any truly correct answer for this. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
