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i965/gen9+: Switch thread scratch space to non-coherent stateless access.

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The thread scratch space is thread-local so using the full IA-coherent
stateless surface index (255 since Gen8) is unnecessary and
potentially expensive.  On Gen8 and early steppings of Gen9 this is
not a functional change because the kernel already sets bit 4 of
HDC_CHICKEN0 which overrides all HDC memory access to be non-coherent
in order to workaround a hardware bug.

This happens to fix a full system hang when running any spilling code
on a pre-production SKL GT4e machine I have on my desk (forcing all
HDC access to non-coherent from the kernel up to stepping F0 might be
a good idea though regardless of this patch), and improves performance
of the OglPSBump2 SynMark benchmark run with INTEL_DEBUG=spill_fs by
33% (11 runs, 5% significance) on a production SKL GT2 (on which HDC
IA-coherency is apparently functional so it wouldn't make sense to
disable globally).

Reviewed-by: Kristian Høgsberg  <krh@bitplanet.net>
This commit is contained in:
Francisco Jerez 2015-11-23 19:18:26 +02:00
parent bc8182808a
commit 55ffa64daf
3 changed files with 19 additions and 4 deletions
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2
src/mesa/drivers/dri/i965/brw_eu.h
View file

@ -315,6 +315,8 @@ void brw_oword_block_read(struct brw_codegen *p,
uint32_t offset,
uint32_t bind_table_index);
unsigned brw_scratch_surface_idx(const struct brw_codegen *p);
void brw_oword_block_read_scratch(struct brw_codegen *p,
struct brw_reg dest,
struct brw_reg mrf,

17
src/mesa/drivers/dri/i965/brw_eu_emit.c
View file

@ -1997,6 +1997,19 @@ void gen6_math(struct brw_codegen *p,
brw_set_src1(p, insn, src1);
}
/**
* Return the right surface index to access the thread scratch space using
* stateless dataport messages.
*/
unsigned
brw_scratch_surface_idx(const struct brw_codegen *p)
{
/* The scratch space is thread-local so IA coherency is unnecessary. */
if (p->devinfo->gen >= 8)
return GEN8_BTI_STATELESS_NON_COHERENT;
else
return BRW_BTI_STATELESS;
}
/**
* Write a block of OWORDs (half a GRF each) from the scratch buffer,
@ -2097,7 +2110,7 @@ void brw_oword_block_write_scratch(struct brw_codegen *p,
brw_set_dp_write_message(p,
insn,
255, /* binding table index (255=stateless) */
brw_scratch_surface_idx(p),
msg_control,
msg_type,
mlen,
@ -2183,7 +2196,7 @@ brw_oword_block_read_scratch(struct brw_codegen *p,
brw_set_dp_read_message(p,
insn,
255, /* binding table index (255=stateless) */
brw_scratch_surface_idx(p),
msg_control,
BRW_DATAPORT_READ_MESSAGE_OWORD_BLOCK_READ, /* msg_type */
BRW_DATAPORT_READ_TARGET_RENDER_CACHE,

4
src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
View file

@ -802,7 +802,7 @@ generate_scratch_read(struct brw_codegen *p,
if (devinfo->gen < 6)
brw_inst_set_cond_modifier(devinfo, send, inst->base_mrf);
brw_set_dp_read_message(p, send,
255, /* binding table index: stateless access */
brw_scratch_surface_idx(p),
BRW_DATAPORT_OWORD_DUAL_BLOCK_1OWORD,
msg_type,
BRW_DATAPORT_READ_TARGET_RENDER_CACHE,
@ -875,7 +875,7 @@ generate_scratch_write(struct brw_codegen *p,
if (devinfo->gen < 6)
brw_inst_set_cond_modifier(p->devinfo, send, inst->base_mrf);
brw_set_dp_write_message(p, send,
255, /* binding table index: stateless access */
brw_scratch_surface_idx(p),
BRW_DATAPORT_OWORD_DUAL_BLOCK_1OWORD,
msg_type,
3, /* mlen */