On 03/05/2018 07:36, Chris Wilson wrote:
Limit the arbitration (where preemption may occur) to inside the batch,
and prevent it from happening on the pipecontrols/flushes we use to
write the breadcrumb seqno. Once the user batch is complete, we have
nothing left to do but serialise and emit the breadcrumb; switching
contexts at this point is futile so don't.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Cc: Michel Thierry <michel.thierry@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_lrc.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index e04798e98db2..70b722c36e65 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1934,7 +1934,7 @@ static int gen8_emit_bb_start(struct i915_request *rq,
rq->ctx->ppgtt->pd_dirty_rings &= ~intel_engine_flag(rq->engine);
}
- cs = intel_ring_begin(rq, 4);
+ cs = intel_ring_begin(rq, 6);
if (IS_ERR(cs))
return PTR_ERR(cs);
@@ -1963,6 +1963,9 @@ static int gen8_emit_bb_start(struct i915_request *rq,
(flags & I915_DISPATCH_RS ? MI_BATCH_RESOURCE_STREAMER : 0);
*cs++ = lower_32_bits(offset);
*cs++ = upper_32_bits(offset);
+
+ *cs++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;
+ *cs++ = MI_NOOP;
intel_ring_advance(rq, cs);
return 0;
@@ -2105,7 +2108,7 @@ static void gen8_emit_breadcrumb(struct i915_request *request, u32 *cs)
cs = gen8_emit_ggtt_write(cs, request->global_seqno,
intel_hws_seqno_address(request->engine));
*cs++ = MI_USER_INTERRUPT;
- *cs++ = MI_NOOP;
+ *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
request->tail = intel_ring_offset(request, cs);
assert_ring_tail_valid(request->ring, request->tail);
@@ -2121,7 +2124,7 @@ static void gen8_emit_breadcrumb_rcs(struct i915_request *request, u32 *cs)
cs = gen8_emit_ggtt_write_rcs(cs, request->global_seqno,
intel_hws_seqno_address(request->engine));
*cs++ = MI_USER_INTERRUPT;
- *cs++ = MI_NOOP;
+ *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
request->tail = intel_ring_offset(request, cs);
assert_ring_tail_valid(request->ring, request->tail);
Sounds to me like a completely sensible thing to do.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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