On Mon, Apr 28, 2014 at 08:22:08AM -0700, bradley.d.vol...@intel.com wrote:
> From: Brad Volkin <bradley.d.vol...@intel.com>
>
> For clients that submit large batch buffers the command parser has
> a substantial impact on performance. On my HSW ULT system performance
> drops as much as ~20% on some tests. Most of the time is spent in the
> command lookup code. Converting that from the current naive search to
> a hash table lookup reduces the performance impact by as much as ~10%.
>
> The choice of value for I915_CMD_HASH_ORDER allows all commands
> currently used in the parser tables to hash to their own bucket (except
> for one collision on the render ring). The tradeoff is that it wastes
> memory. Because the opcodes for the commands in the tables are not
> particularly well distributed, reducing the order still leaves many
> buckets empty. The increased collisions don't seem to have a huge
> impact on the performance gain, but for now anyhow, the parser trades
> memory for performance.
>
> Signed-off-by: Brad Volkin <bradley.d.vol...@intel.com>
Nice. One idea on top which could be worth a shot is a bloomfilter to
handle all the non-special cases without a (likely) cache miss in the
hashtable. The per-ring bloomfilter would be only loaded once (and if we
place it nearby other stuff the cmdparser needs anyway even that is
amortized).
Also Chris mentioned that blitter loads under X are about the worst case
wrt impact of the cmdparser. Benchmarking x11perf might be a useful
extreme testcase for optimizing this. I guess Chris will jump in with more
ideas?
Thanks, Daniel
> ---
> drivers/gpu/drm/i915/i915_cmd_parser.c | 136
> ++++++++++++++++++++++++--------
> drivers/gpu/drm/i915/i915_drv.h | 1 +
> drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +
> drivers/gpu/drm/i915/intel_ringbuffer.h | 11 ++-
> 4 files changed, 116 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c
> b/drivers/gpu/drm/i915/i915_cmd_parser.c
> index 9bac097..9dca899 100644
> --- a/drivers/gpu/drm/i915/i915_cmd_parser.c
> +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
> @@ -498,16 +498,18 @@ static u32 gen7_blt_get_cmd_length_mask(u32 cmd_header)
> return 0;
> }
>
> -static bool validate_cmds_sorted(struct intel_ring_buffer *ring)
> +static bool validate_cmds_sorted(struct intel_ring_buffer *ring,
> + const struct drm_i915_cmd_table *cmd_tables,
> + int cmd_table_count)
> {
> int i;
> bool ret = true;
>
> - if (!ring->cmd_tables || ring->cmd_table_count == 0)
> + if (!cmd_tables || cmd_table_count == 0)
> return true;
>
> - for (i = 0; i < ring->cmd_table_count; i++) {
> - const struct drm_i915_cmd_table *table = &ring->cmd_tables[i];
> + for (i = 0; i < cmd_table_count; i++) {
> + const struct drm_i915_cmd_table *table = &cmd_tables[i];
> u32 previous = 0;
> int j;
>
> @@ -557,6 +559,60 @@ static bool validate_regs_sorted(struct
> intel_ring_buffer *ring)
> ring->master_reg_count);
> }
>
> +struct cmd_node {
> + const struct drm_i915_cmd_descriptor *desc;
> + struct hlist_node node;
> +};
> +
> +/*
> + * Different command ranges have different numbers of bits for the opcode.
> + * In order to use the opcode bits, and only the opcode bits, for the hash
> key
> + * we should use the MI_* command opcode mask (since those commands use the
> + * fewest bits for the opcode.)
> + */
> +#define CMD_HASH_MASK STD_MI_OPCODE_MASK
> +
> +static int init_hash_table(struct intel_ring_buffer *ring,
> + const struct drm_i915_cmd_table *cmd_tables,
> + int cmd_table_count)
> +{
> + int i, j;
> +
> + hash_init(ring->cmd_hash);
> +
> + for (i = 0; i < cmd_table_count; i++) {
> + const struct drm_i915_cmd_table *table = &cmd_tables[i];
> +
> + for (j = 0; j < table->count; j++) {
> + const struct drm_i915_cmd_descriptor *desc =
> + &table->table[j];
> + struct cmd_node *desc_node =
> + kmalloc(sizeof(*desc_node), GFP_KERNEL);
> +
> + if (!desc_node)
> + return -ENOMEM;
> +
> + desc_node->desc = desc;
> + hash_add(ring->cmd_hash, &desc_node->node,
> + desc->cmd.value & CMD_HASH_MASK);
> + }
> + }
> +
> + return 0;
> +}
> +
> +static void fini_hash_table(struct intel_ring_buffer *ring)
> +{
> + struct hlist_node *tmp;
> + struct cmd_node *desc_node;
> + int i;
> +
> + hash_for_each_safe(ring->cmd_hash, i, tmp, desc_node, node) {
> + hash_del(&desc_node->node);
> + kfree(desc_node);
> + }
> +}
> +
> /**
> * i915_cmd_parser_init_ring() - set cmd parser related fields for a
> ringbuffer
> * @ring: the ringbuffer to initialize
> @@ -567,18 +623,21 @@ static bool validate_regs_sorted(struct
> intel_ring_buffer *ring)
> */
> void i915_cmd_parser_init_ring(struct intel_ring_buffer *ring)
> {
> + const struct drm_i915_cmd_table *cmd_tables;
> + int cmd_table_count;
> +
> if (!IS_GEN7(ring->dev))
> return;
>
> switch (ring->id) {
> case RCS:
> if (IS_HASWELL(ring->dev)) {
> - ring->cmd_tables = hsw_render_ring_cmds;
> - ring->cmd_table_count =
> + cmd_tables = hsw_render_ring_cmds;
> + cmd_table_count =
> ARRAY_SIZE(hsw_render_ring_cmds);
> } else {
> - ring->cmd_tables = gen7_render_cmds;
> - ring->cmd_table_count = ARRAY_SIZE(gen7_render_cmds);
> + cmd_tables = gen7_render_cmds;
> + cmd_table_count = ARRAY_SIZE(gen7_render_cmds);
> }
>
> ring->reg_table = gen7_render_regs;
> @@ -595,17 +654,17 @@ void i915_cmd_parser_init_ring(struct intel_ring_buffer
> *ring)
> ring->get_cmd_length_mask = gen7_render_get_cmd_length_mask;
> break;
> case VCS:
> - ring->cmd_tables = gen7_video_cmds;
> - ring->cmd_table_count = ARRAY_SIZE(gen7_video_cmds);
> + cmd_tables = gen7_video_cmds;
> + cmd_table_count = ARRAY_SIZE(gen7_video_cmds);
> ring->get_cmd_length_mask = gen7_bsd_get_cmd_length_mask;
> break;
> case BCS:
> if (IS_HASWELL(ring->dev)) {
> - ring->cmd_tables = hsw_blt_ring_cmds;
> - ring->cmd_table_count = ARRAY_SIZE(hsw_blt_ring_cmds);
> + cmd_tables = hsw_blt_ring_cmds;
> + cmd_table_count = ARRAY_SIZE(hsw_blt_ring_cmds);
> } else {
> - ring->cmd_tables = gen7_blt_cmds;
> - ring->cmd_table_count = ARRAY_SIZE(gen7_blt_cmds);
> + cmd_tables = gen7_blt_cmds;
> + cmd_table_count = ARRAY_SIZE(gen7_blt_cmds);
> }
>
> ring->reg_table = gen7_blt_regs;
> @@ -622,8 +681,8 @@ void i915_cmd_parser_init_ring(struct intel_ring_buffer
> *ring)
> ring->get_cmd_length_mask = gen7_blt_get_cmd_length_mask;
> break;
> case VECS:
> - ring->cmd_tables = hsw_vebox_cmds;
> - ring->cmd_table_count = ARRAY_SIZE(hsw_vebox_cmds);
> + cmd_tables = hsw_vebox_cmds;
> + cmd_table_count = ARRAY_SIZE(hsw_vebox_cmds);
> /* VECS can use the same length_mask function as VCS */
> ring->get_cmd_length_mask = gen7_bsd_get_cmd_length_mask;
> break;
> @@ -633,18 +692,38 @@ void i915_cmd_parser_init_ring(struct intel_ring_buffer
> *ring)
> BUG();
> }
>
> - BUG_ON(!validate_cmds_sorted(ring));
> + BUG_ON(!validate_cmds_sorted(ring, cmd_tables, cmd_table_count));
> BUG_ON(!validate_regs_sorted(ring));
> +
> + BUG_ON(init_hash_table(ring, cmd_tables, cmd_table_count));
> +
> + ring->needs_cmd_parser = true;
> +}
> +
> +/**
> + * i915_cmd_parser_fini_ring() - clean up cmd parser related fields
> + * @ring: the ringbuffer to clean up
> + *
> + * Releases any resources related to command parsing that may have been
> + * initialized for the specified ring.
> + */
> +void i915_cmd_parser_fini_ring(struct intel_ring_buffer *ring)
> +{
> + if (!ring->needs_cmd_parser)
> + return;
> +
> + fini_hash_table(ring);
> }
>
> static const struct drm_i915_cmd_descriptor*
> -find_cmd_in_table(const struct drm_i915_cmd_table *table,
> +find_cmd_in_table(struct intel_ring_buffer *ring,
> u32 cmd_header)
> {
> - int i;
> + struct cmd_node *desc_node;
>
> - for (i = 0; i < table->count; i++) {
> - const struct drm_i915_cmd_descriptor *desc = &table->table[i];
> + hash_for_each_possible(ring->cmd_hash, desc_node, node,
> + cmd_header & CMD_HASH_MASK) {
> + const struct drm_i915_cmd_descriptor *desc = desc_node->desc;
> u32 masked_cmd = desc->cmd.mask & cmd_header;
> u32 masked_value = desc->cmd.value & desc->cmd.mask;
>
> @@ -668,16 +747,12 @@ find_cmd(struct intel_ring_buffer *ring,
> u32 cmd_header,
> struct drm_i915_cmd_descriptor *default_desc)
> {
> + const struct drm_i915_cmd_descriptor *desc;
> u32 mask;
> - int i;
> -
> - for (i = 0; i < ring->cmd_table_count; i++) {
> - const struct drm_i915_cmd_descriptor *desc;
>
> - desc = find_cmd_in_table(&ring->cmd_tables[i], cmd_header);
> - if (desc)
> - return desc;
> - }
> + desc = find_cmd_in_table(ring, cmd_header);
> + if (desc)
> + return desc;
>
> mask = ring->get_cmd_length_mask(cmd_header);
> if (!mask)
> @@ -748,8 +823,7 @@ bool i915_needs_cmd_parser(struct intel_ring_buffer *ring)
> {
> struct drm_i915_private *dev_priv = ring->dev->dev_private;
>
> - /* No command tables indicates a platform without parsing */
> - if (!ring->cmd_tables)
> + if (!ring->needs_cmd_parser)
> return false;
>
> /*
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 7d6acb4..8c8388f 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2414,6 +2414,7 @@ const char *i915_cache_level_str(int type);
> /* i915_cmd_parser.c */
> int i915_cmd_parser_get_version(void);
> void i915_cmd_parser_init_ring(struct intel_ring_buffer *ring);
> +void i915_cmd_parser_fini_ring(struct intel_ring_buffer *ring);
> bool i915_needs_cmd_parser(struct intel_ring_buffer *ring);
> int i915_parse_cmds(struct intel_ring_buffer *ring,
> struct drm_i915_gem_object *batch_obj,
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c
> b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index eb3dd26..06fa9a3 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1469,6 +1469,8 @@ void intel_cleanup_ring_buffer(struct intel_ring_buffer
> *ring)
> ring->cleanup(ring);
>
> cleanup_status_page(ring);
> +
> + i915_cmd_parser_fini_ring(ring);
> }
>
> static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n)
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h
> b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index 413cdc7..48daa91 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -1,6 +1,10 @@
> #ifndef _INTEL_RINGBUFFER_H_
> #define _INTEL_RINGBUFFER_H_
>
> +#include <linux/hashtable.h>
> +
> +#define I915_CMD_HASH_ORDER 9
> +
> /*
> * Gen2 BSpec "1. Programming Environment" / 1.4.4.6 "Ring Buffer Use"
> * Gen3 BSpec "vol1c Memory Interface Functions" / 2.3.4.5 "Ring Buffer Use"
> @@ -164,12 +168,13 @@ struct intel_ring_buffer {
> volatile u32 *cpu_page;
> } scratch;
>
> + bool needs_cmd_parser;
> +
> /*
> - * Tables of commands the command parser needs to know about
> + * Table of commands the command parser needs to know about
> * for this ring.
> */
> - const struct drm_i915_cmd_table *cmd_tables;
> - int cmd_table_count;
> + DECLARE_HASHTABLE(cmd_hash, I915_CMD_HASH_ORDER);
>
> /*
> * Table of registers allowed in commands that read/write registers.
> --
> 1.8.3.2
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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