Re: [igt-dev] [PATCH i-g-t] benchmarks/gem_wsim: Heap allocate VLA structs

["Ser, Simon" <simon.ser@intel.com>]

On Fri, 2019-05-24 at 08:25 +0100, Chris Wilson wrote:
> Apparently VLA structs (e.g. struct { int array[count] }) is a gcc
> extension that clang refuses to support as handling memory layout is too
> difficult for it.
> 
> Move the on-stack VLA to the heap.

IMHO using an upper bound would be much simpler.

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>  benchmarks/gem_wsim.c | 146 +++++++++++++++++++++++++++---------------
>  1 file changed, 95 insertions(+), 51 deletions(-)
> 
> diff --git a/benchmarks/gem_wsim.c b/benchmarks/gem_wsim.c
> index e2ffb93a9..0a0032bff 100644
> --- a/benchmarks/gem_wsim.c
> +++ b/benchmarks/gem_wsim.c
> @@ -1441,6 +1441,48 @@ set_ctx_sseu(struct ctx *ctx, uint64_t slice_mask)
>  	return slice_mask;
>  }
>  
> +static size_t sizeof_load_balance(int count)
> +{
> +	struct i915_context_engines_load_balance *ptr;
> +
> +	assert(sizeof(ptr->engines[count]) == count * sizeof(ptr->engines[0]));
> +	return sizeof(*ptr) + sizeof(ptr->engines[count]);
> +}
> +
> +static struct i915_context_engines_load_balance *
> +alloc_load_balance(int count)
> +{
> +	return calloc(1, sizeof_load_balance(count));
> +}
> +
> +static size_t sizeof_param_engines(int count)
> +{
> +	struct i915_context_param_engines *ptr;
> +
> +	assert(sizeof(ptr->engines[count]) == count * sizeof(ptr->engines[0]));
> +	return sizeof(*ptr) + sizeof(ptr->engines[count]);
> +}
> +
> +static struct i915_context_param_engines *
> +alloc_param_engines(int count)
> +{
> +	return calloc(1, sizeof_param_engines(count));
> +}
> +
> +static size_t sizeof_engines_bond(int count)
> +{
> +	struct i915_context_engines_bond *ptr;
> +
> +	assert(sizeof(ptr->engines[count]) == count * sizeof(ptr->engines[0]));
> +	return sizeof(*ptr) + sizeof(ptr->engines[count]);
> +}
> +
> +static struct i915_context_engines_bond *
> +alloc_engines_bond(int count)
> +{
> +	return calloc(1, sizeof_engines_bond(count));
> +}
> +
>  static int
>  prepare_workload(unsigned int id, struct workload *wrk, unsigned int flags)
>  {
> @@ -1676,66 +1718,54 @@ prepare_workload(unsigned int id, struct workload *wrk, unsigned int flags)
>  		}
>  
>  		if (ctx->engine_map) {
> -			I915_DEFINE_CONTEXT_PARAM_ENGINES(set_engines,
> -							  ctx->engine_map_count + 1);
> -			I915_DEFINE_CONTEXT_ENGINES_LOAD_BALANCE(load_balance,
> -								 ctx->engine_map_count);
> +			struct i915_context_param_engines *set_engines =
> +				alloc_param_engines(ctx->engine_map_count + 1);
> +			struct i915_context_engines_load_balance *load_balance =
> +				alloc_load_balance(ctx->engine_map_count);
>  			struct drm_i915_gem_context_param param = {
>  				.ctx_id = ctx_id,
>  				.param = I915_CONTEXT_PARAM_ENGINES,
> -				.size = sizeof(set_engines),
> -				.value = to_user_pointer(&set_engines),
> +				.size = sizeof_param_engines(ctx->engine_map_count + 1),
> +				.value = to_user_pointer(set_engines),
>  			};
> +			struct i915_context_engines_bond *last = NULL;
>  
>  			if (ctx->wants_balance) {
> -				set_engines.extensions =
> -					to_user_pointer(&load_balance);
> +				set_engines->extensions =
> +					to_user_pointer(load_balance);
>  
> -				memset(&load_balance, 0, sizeof(load_balance));
> -				load_balance.base.name =
> +				load_balance->base.name =
>  					I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE;
> -				load_balance.num_siblings =
> +				load_balance->num_siblings =
>  					ctx->engine_map_count;
>  
>  				for (j = 0; j < ctx->engine_map_count; j++)
> -					load_balance.engines[j] =
> +					load_balance->engines[j] =
>  						get_engine(ctx->engine_map[j]);
> -			} else {
> -				set_engines.extensions = 0;
>  			}
>  
>  			/* Reserve slot for virtual engine. */
> -			set_engines.engines[0].engine_class =
> +			set_engines->engines[0].engine_class =
>  				I915_ENGINE_CLASS_INVALID;
> -			set_engines.engines[0].engine_instance =
> +			set_engines->engines[0].engine_instance =
>  				I915_ENGINE_CLASS_INVALID_NONE;
>  
>  			for (j = 1; j <= ctx->engine_map_count; j++)
> -				set_engines.engines[j] =
> +				set_engines->engines[j] =
>  					get_engine(ctx->engine_map[j - 1]);
>  
> +			last = NULL;
>  			for (j = 0; j < ctx->bond_count; j++) {
>  				unsigned long mask = ctx->bonds[j].mask;
> -				I915_DEFINE_CONTEXT_ENGINES_BOND(bond,
> -								 __builtin_popcount(mask));
> -				struct i915_context_engines_bond *p = NULL, *prev;
> +				struct i915_context_engines_bond *bond =
> +					alloc_engines_bond(__builtin_popcount(mask));
>  				unsigned int b, e;
>  
> -				prev = p;
> -				p = alloca(sizeof(bond));
> -				assert(p);
> -				memset(p, 0, sizeof(bond));
> -
> -				if (j == 0)
> -					load_balance.base.next_extension =
> -						to_user_pointer(p);
> -				else if (j < (ctx->bond_count - 1))
> -					prev->base.next_extension =
> -						to_user_pointer(p);
> +				bond->base.next_extension = to_user_pointer(last);
> +				bond->base.name = I915_CONTEXT_ENGINES_EXT_BOND;
>  
> -				p->base.name = I915_CONTEXT_ENGINES_EXT_BOND;
> -				p->virtual_index = 0;
> -				p->master = get_engine(ctx->bonds[j].master);
> +				bond->virtual_index = 0;
> +				bond->master = get_engine(ctx->bonds[j].master);
>  
>  				for (b = 0, e = 0; mask; e++, mask >>= 1) {
>  					unsigned int idx;
> @@ -1743,44 +1773,58 @@ prepare_workload(unsigned int id, struct workload *wrk, unsigned int flags)
>  					if (!(mask & 1))
>  						continue;
>  
> -					idx = find_engine(&set_engines.engines[1],
> +					idx = find_engine(&set_engines->engines[1],
>  							  ctx->engine_map_count,
>  							  e);
> -					p->engines[b++] =
> -						set_engines.engines[1 + idx];
> +					bond->engines[b++] =
> +						set_engines->engines[1 + idx];
>  				}
> +
> +				last = bond;
>  			}
> +			load_balance->base.next_extension = to_user_pointer(last);
>  
>  			gem_context_set_param(fd, &param);
> +
> +			while (last) {
> +				struct i915_context_engines_bond *next =
> +					from_user_pointer(last->base.next_extension);
> +				free(last);
> +				last = next;
> +			}
> +			free(load_balance);
> +			free(set_engines);
>  		} else if (ctx->wants_balance) {
>  			const unsigned int count = num_engines_in_class(VCS);
> -			I915_DEFINE_CONTEXT_ENGINES_LOAD_BALANCE(load_balance,
> -								 count);
> -			I915_DEFINE_CONTEXT_PARAM_ENGINES(set_engines,
> -							  count + 1);
> +			struct i915_context_engines_load_balance *load_balance =
> +				alloc_load_balance(count);
> +			struct i915_context_param_engines *set_engines =
> +				alloc_param_engines(count + 1);
>  			struct drm_i915_gem_context_param param = {
>  				.ctx_id = ctx_id,
>  				.param = I915_CONTEXT_PARAM_ENGINES,
> -				.size = sizeof(set_engines),
> -				.value = to_user_pointer(&set_engines),
> +				.size = sizeof_param_engines(count + 1),
> +				.value = to_user_pointer(set_engines),
>  			};
>  
> -			set_engines.extensions = to_user_pointer(&load_balance);
> +			set_engines->extensions = to_user_pointer(load_balance);
>  
> -			set_engines.engines[0].engine_class =
> +			set_engines->engines[0].engine_class =
>  				I915_ENGINE_CLASS_INVALID;
> -			set_engines.engines[0].engine_instance =
> +			set_engines->engines[0].engine_instance =
>  				I915_ENGINE_CLASS_INVALID_NONE;
> -			fill_engines_class(&set_engines.engines[1], VCS);
> +			fill_engines_class(&set_engines->engines[1], VCS);
>  
> -			memset(&load_balance, 0, sizeof(load_balance));
> -			load_balance.base.name =
> +			load_balance->base.name =
>  				I915_CONTEXT_ENGINES_EXT_LOAD_BALANCE;
> -			load_balance.num_siblings = count;
> +			load_balance->num_siblings = count;
>  
> -			fill_engines_class(&load_balance.engines[0], VCS);
> +			fill_engines_class(&load_balance->engines[0], VCS);
>  
>  			gem_context_set_param(fd, &param);
> +
> +			free(set_engines);
> +			free(load_balance);
>  		}
>  
>  		if (wrk->sseu) {
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx