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i965/query: Cache whether the batch references the query BO.

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Chris Wilson noted that repeated calls to CheckQuery() would call
drm_intel_bo_references(brw->batch.bo, query->bo) on each invocation,
which is expensive.  Once we've flushed, we know that future batches
won't reference query->bo, so there's no point in asking more than once.

This patch adds a brw_query_object::flushed flag, which is a
conservative estimate of whether the batch has been flushed.

On the first call to CheckQuery() or WaitQuery(), we check if the
batch references query->bo.  If not, it must have been flushed for
some reason (such as being full).  We record that it was flushed.
If it does reference query->bo, we explicitly flush, and record that
we did so.

Any subsequent checks will simply see that query->flushed is set,
and skip the drm_intel_bo_references() call.

Inspired by a patch from Chris Wilson.

According to Eero, this does not affect the performance of Witcher 2
on Haswell, but approximately halves the userspace CPU usage.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86969
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Kenneth Graunke 2014-12-11 02:26:39 -08:00
parent cb5cfb8361
commit 3eb6258db7
2 changed files with 26 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
src/mesa/drivers/dri/i965/brw_context.h
View file

@ -831,6 +831,9 @@ struct brw_query_object {
/** Last index in bo with query data for this object. */
int last_index;
/** True if we know the batch has been flushed since we ended the query. */
bool flushed;
};
struct intel_sync_object {

27
src/mesa/drivers/dri/i965/gen6_queryobj.c
View file

@ -281,6 +281,27 @@ gen6_end_query(struct gl_context *ctx, struct gl_query_object *q)
default:
unreachable("Unrecognized query target in brw_end_query()");
}
/* The current batch contains the commands to handle EndQuery(),
* but they won't actually execute until it is flushed.
*/
query->flushed = false;
}
/**
* Flush the batch if it still references the query object BO.
*/
static void
flush_batch_if_needed(struct brw_context *brw, struct brw_query_object *query)
{
/* If the batch doesn't reference the BO, it must have been flushed
* (for example, due to being full). Record that it's been flushed.
*/
query->flushed = query->flushed ||
!drm_intel_bo_references(brw->batch.bo, query->bo);
if (!query->flushed)
intel_batchbuffer_flush(brw);
}
/**
@ -298,8 +319,7 @@ static void gen6_wait_query(struct gl_context *ctx, struct gl_query_object *q)
* still contributing to it, flush it now to finish that work so the
* result will become available (eventually).
*/
if (drm_intel_bo_references(brw->batch.bo, query->bo))
intel_batchbuffer_flush(brw);
flush_batch_if_needed(brw, query);
gen6_queryobj_get_results(ctx, query);
}
@ -328,8 +348,7 @@ static void gen6_check_query(struct gl_context *ctx, struct gl_query_object *q)
* not ready yet on the first time it is queried. This ensures that
* the async query will return true in finite time.
*/
if (drm_intel_bo_references(brw->batch.bo, query->bo))
intel_batchbuffer_flush(brw);
flush_batch_if_needed(brw, query);
if (!drm_intel_bo_busy(query->bo)) {
gen6_queryobj_get_results(ctx, query);