[Intel-gfx] [PATCH v5 1/7] drm/i915: Implement a framework for batch buffer pools
Bloomfield, Jon
jon.bloomfield at intel.com
Mon Dec 8 07:19:59 PST 2014
> -----Original Message-----
> From: Nguyen, Michael H
> Sent: Wednesday, November 26, 2014 9:54 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: Bloomfield, Jon; Volkin, Bradley D
> Subject: [PATCH v5 1/7] drm/i915: Implement a framework for batch buffer
> pools
>
> From: Brad Volkin <bradley.d.volkin at intel.com>
>
> This adds a small module for managing a pool of batch buffers.
> The only current use case is for the command parser, as described in the
> kerneldoc in the patch. The code is simple, but separating it out makes it
> easier to change the underlying algorithms and to extend to future use cases
> should they arise.
>
> The interface is simple: init to create an empty pool, fini to clean it up, get to
> obtain a new buffer. Note that all buffers are expected to be inactive before
> cleaning up the pool.
>
> Locking is currently based on the caller holding the struct_mutex.
> We already do that in the places where we will use the batch pool for the
> command parser.
>
> v2:
> - s/BUG_ON/WARN_ON/ for locking assertions
> - Remove the cap on pool size
> - Switch from alloc/free to init/fini
>
> v3:
> - Idiomatic looping structure in _fini
> - Correct handling of purged objects
> - Don't return a buffer that's too much larger than needed
>
> v4:
> - Rebased to latest -nightly
>
> v5:
> - Remove _put() function and clean up comments to match
>
> v6:
> - Move purged check inside the loop (danvet, from v4 1/7 feedback)
>
> Issue: VIZ-4719
> Signed-off-by: Brad Volkin <bradley.d.volkin at intel.com>
> ---
> Documentation/DocBook/drm.tmpl | 5 +
> drivers/gpu/drm/i915/Makefile | 1 +
> drivers/gpu/drm/i915/i915_drv.h | 15 +++
> drivers/gpu/drm/i915/i915_gem.c | 1 +
> drivers/gpu/drm/i915/i915_gem_batch_pool.c | 152
> +++++++++++++++++++++++++++++
> 5 files changed, 174 insertions(+)
> create mode 100644 drivers/gpu/drm/i915/i915_gem_batch_pool.c
>
> diff --git a/Documentation/DocBook/drm.tmpl
> b/Documentation/DocBook/drm.tmpl index 944e8ed..b5943d4 100644
> --- a/Documentation/DocBook/drm.tmpl
> +++ b/Documentation/DocBook/drm.tmpl
> @@ -4028,6 +4028,11 @@ int num_ioctls;</synopsis>
> !Idrivers/gpu/drm/i915/i915_cmd_parser.c
> </sect2>
> <sect2>
> + <title>Batchbuffer Pools</title>
> +!Pdrivers/gpu/drm/i915/i915_gem_batch_pool.c batch pool
> +!Idrivers/gpu/drm/i915/i915_gem_batch_pool.c
> + </sect2>
> + <sect2>
> <title>Logical Rings, Logical Ring Contexts and Execlists</title>
> !Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and
> Execlists !Idrivers/gpu/drm/i915/intel_lrc.c
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index e4083e4..c8dbb37d 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -19,6 +19,7 @@ i915-$(CONFIG_DEBUG_FS) += i915_debugfs.o
>
> # GEM code
> i915-y += i915_cmd_parser.o \
> + i915_gem_batch_pool.o \
> i915_gem_context.o \
> i915_gem_render_state.o \
> i915_gem_debug.o \
> diff --git a/drivers/gpu/drm/i915/i915_drv.h
> b/drivers/gpu/drm/i915/i915_drv.h index c4f2cb6..b12a062 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1154,6 +1154,12 @@ struct intel_l3_parity {
> int which_slice;
> };
>
> +struct i915_gem_batch_pool {
> + struct drm_device *dev;
> + struct list_head active_list;
> + struct list_head inactive_list;
> +};
> +
> struct i915_gem_mm {
> /** Memory allocator for GTT stolen memory */
> struct drm_mm stolen;
> @@ -1885,6 +1891,8 @@ struct drm_i915_gem_object {
> /** Used in execbuf to temporarily hold a ref */
> struct list_head obj_exec_link;
>
> + struct list_head batch_pool_list;
> +
> /**
> * This is set if the object is on the active lists (has pending
> * rendering and so a non-zero seqno), and is not set if it i s on @@ -
> 2849,6 +2857,13 @@ void i915_destroy_error_state(struct drm_device
> *dev); void i915_get_extra_instdone(struct drm_device *dev, uint32_t
> *instdone); const char *i915_cache_level_str(struct drm_i915_private *i915,
> int type);
>
> +/* i915_gem_batch_pool.c */
> +void i915_gem_batch_pool_init(struct drm_device *dev,
> + struct i915_gem_batch_pool *pool); void
> +i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool); struct
> +drm_i915_gem_object* i915_gem_batch_pool_get(struct
> i915_gem_batch_pool
> +*pool, size_t size);
> +
> /* i915_cmd_parser.c */
> int i915_cmd_parser_get_version(void);
> int i915_cmd_parser_init_ring(struct intel_engine_cs *ring); diff --git
> a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 86cf428..b19dd06 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4433,6 +4433,7 @@ void i915_gem_object_init(struct
> drm_i915_gem_object *obj,
> INIT_LIST_HEAD(&obj->ring_list);
> INIT_LIST_HEAD(&obj->obj_exec_link);
> INIT_LIST_HEAD(&obj->vma_list);
> + INIT_LIST_HEAD(&obj->batch_pool_list);
>
> obj->ops = ops;
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_batch_pool.c
> b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
> new file mode 100644
> index 0000000..ccbe8f9
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/i915_gem_batch_pool.c
> @@ -0,0 +1,152 @@
> +/*
> + * Copyright © 2014 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person
> +obtaining a
> + * copy of this software and associated documentation files (the
> +"Software"),
> + * to deal in the Software without restriction, including without
> +limitation
> + * the rights to use, copy, modify, merge, publish, distribute,
> +sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom
> +the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the
> +next
> + * paragraph) shall be included in all copies or substantial portions
> +of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> +EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> +MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
> EVENT
> +SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
> DAMAGES OR
> +OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> +ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> OTHER
> +DEALINGS
> + * IN THE SOFTWARE.
> + *
> + */
> +
> +#include "i915_drv.h"
> +
> +/**
> + * DOC: batch pool
> + *
> + * In order to submit batch buffers as 'secure', the software command
> +parser
> + * must ensure that a batch buffer cannot be modified after parsing. It
> +does
> + * this by copying the user provided batch buffer contents to a kernel
> +owned
> + * buffer from which the hardware will actually execute, and by
> +carefully
> + * managing the address space bindings for such buffers.
> + *
> + * The batch pool framework provides a mechanism for the driver to
> +manage a
> + * set of scratch buffers to use for this purpose. The framework can be
> + * extended to support other uses cases should they arise.
> + */
> +
> +/**
> + * i915_gem_batch_pool_init() - initialize a batch buffer pool
> + * @dev: the drm device
> + * @pool: the batch buffer pool
> + */
> +void i915_gem_batch_pool_init(struct drm_device *dev,
> + struct i915_gem_batch_pool *pool) {
> + pool->dev = dev;
> + INIT_LIST_HEAD(&pool->active_list);
> + INIT_LIST_HEAD(&pool->inactive_list);
> +}
> +
> +/**
> + * i915_gem_batch_pool_fini() - clean up a batch buffer pool
> + * @pool: the pool to clean up
> + *
> + * Note: Callers must hold the struct_mutex.
> + */
> +void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool) {
> + WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
> +
> + while (!list_empty(&pool->active_list)) {
> + struct drm_i915_gem_object *obj =
> + list_first_entry(&pool->active_list,
> + struct drm_i915_gem_object,
> + batch_pool_list);
> +
> + WARN_ON(obj->active);
> +
> + list_del_init(&obj->batch_pool_list);
> + drm_gem_object_unreference(&obj->base);
> + }
> +
> + while (!list_empty(&pool->inactive_list)) {
> + struct drm_i915_gem_object *obj =
> + list_first_entry(&pool->inactive_list,
> + struct drm_i915_gem_object,
> + batch_pool_list);
> +
> + list_del_init(&obj->batch_pool_list);
> + drm_gem_object_unreference(&obj->base);
> + }
> +}
> +
> +/**
> + * i915_gem_batch_pool_get() - select a buffer from the pool
> + * @pool: the batch buffer pool
> + * @size: the minimum desired size of the returned buffer
> + *
> + * Finds or allocates a batch buffer in the pool with at least the
> +requested
> + * size. The caller is responsible for any domain, active/inactive, or
> + * purgeability management for the returned buffer.
> + *
> + * Note: Callers must hold the struct_mutex
> + *
> + * Return: the selected batch buffer object */ struct
> +drm_i915_gem_object * i915_gem_batch_pool_get(struct
> +i915_gem_batch_pool *pool,
> + size_t size)
> +{
> + struct drm_i915_gem_object *obj = NULL;
> + struct drm_i915_gem_object *tmp, *next;
> + bool was_purged;
> +
> + WARN_ON(!mutex_is_locked(&pool->dev->struct_mutex));
> +
> + list_for_each_entry_safe(tmp, next,
> + &pool->active_list, batch_pool_list) {
> + if (!tmp->active)
> + list_move_tail(&tmp->batch_pool_list,
> + &pool->inactive_list);
> + }
> +
> + do {
> + was_purged = false;
> +
> + list_for_each_entry_safe(tmp, next,
> + &pool->inactive_list, batch_pool_list) {
> + /*
> + * Select a buffer that is at least as big as needed
> + * but not 'too much' bigger. A better way to do this
> + * might be to bucket the pool objects based on size.
> + */
> + if (tmp->base.size >= size &&
> + tmp->base.size <= (2 * size)) {
> + obj = tmp;
> + break;
> + }
> +
> + if (tmp->madv == __I915_MADV_PURGED) {
> + was_purged = true;
> + list_del(&tmp->batch_pool_list);
> + drm_gem_object_unreference(&tmp-
> >base);
> + }
> + }
> + } while (was_purged);
I don't understand what the outer-loop/was_purged is trying to do here.
I might be missing something subtle, but the following scenarios seem to have issues:
1) There are no suitable objects in the pool, but there are purgeable objects
We'll loop through the whole list, purging any puregable objects.
On completion of the inner loop, was_purged==true, so we'll go back through the
whole list again. We still won't find any suitable objects, and won't find any more
purgeable objects either, so the second pass is redundant.
2) There is a suitable object, but there are purgeable objects before it
We'll purge objects up to the first suitable object, and break out of the inner loop
We'll then go back through a second time because was_purged is set, and select
the exact same object as we selected last time.
Any purgeable objects after the selected object will remain un-purged
If the intention here is to ensure we always purge all purgeable objects, then I
think we just need to remove the break, and the outer-loop, along with was_purged.
This will always traverse the entire list, and end with obj set to the last suitable object
in the list (if any).
If you want to be optimal you could adjust the condition to only choose objects that are
smaller than any previously selected object.
> +
> + if (!obj) {
> + obj = i915_gem_alloc_object(pool->dev, size);
> + if (!obj)
> + return ERR_PTR(-ENOMEM);
> +
> + list_add_tail(&obj->batch_pool_list, &pool->inactive_list);
> + }
> +
> + list_move_tail(&obj->batch_pool_list, &pool->active_list);
> +
> + return obj;
> +}
> --
> 1.9.1
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