Quoting Kenneth Graunke (2017-09-13 21:54:13)
> +/**
> + * Target sizes of the batch and state buffers. We create the initial
> + * buffers at these sizes, and flush when they're nearly full. If we
> + * underestimate how close we are to the end, and suddenly need more space
> + * in the middle of a draw, we can grow the buffers, and finish the draw.
> + * At that point, we'll be over our target size, so the next operation
> + * should flush. Each time we flush the batch, we recreate both buffers
> + * at the original target size, so it doesn't grow without bound.
> + */
> #define BATCH_SZ (8192*sizeof(uint32_t))
> #define STATE_SZ (8192*sizeof(uint32_t))
>
> +/* The kernel assumes batchbuffers are smaller than 256kB. */
> +#define MAX_BATCH_SIZE (256 * 1024)
> +
> +/* 3DSTATE_BINDING_TABLE_POINTERS has a U16 offset from Surface State Base
> + * Address, which means that we can't put binding tables beyond 64kB. This
> + * effectively limits the maximum statebuffer size to 64kB.
> + */
> +#define MAX_STATE_SIZE (64 * 1024)
> +static void
> +grow_buffer(struct brw_context *brw,
> + struct brw_bo **bo_ptr,
> + uint32_t **map_ptr,
> + uint32_t **cpu_map_ptr,
> + unsigned existing_bytes,
> + unsigned new_size)
> +{
> + struct intel_batchbuffer *batch = &brw->batch;
> + struct brw_bufmgr *bufmgr = brw->bufmgr;
> +
> + uint32_t *old_map = *map_ptr;
> + struct brw_bo *old_bo = *bo_ptr;
> +
> + struct brw_bo *new_bo = brw_bo_alloc(bufmgr, old_bo->name, new_size,
> 4096);
> + uint32_t *new_map;
> +
> + perf_debug("Growing %s - ran out of space\n", old_bo->name);
> +
> + /* Copy existing data to the new larger buffer */
> + if (*cpu_map_ptr) {
> + *cpu_map_ptr = new_map = realloc(*cpu_map_ptr, new_size);
What I was thinking was for the cpu_map, you know the max size and the
allocation is persistent, so just allocate the max upfront and skip the
realloc (+ implicit copy) of the shadow.
-Chris
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