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![Chris Wilson](/assets/img/avatar_default.png)
To continue the onslaught of removing the assumption of a global execution ordering, another casualty is the engine->timeline. Without an actual timeline to track, it is overkill and we can replace it with a much less grand plain list. We still need a list of requests inflight, for the simple purpose of finding inflight requests (for retiring, resetting, preemption etc). Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190614164606.15633-3-chris@chris-wilson.co.uk
509 lines
14 KiB
C
509 lines
14 KiB
C
/*
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* SPDX-License-Identifier: MIT
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*
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* Copyright © 2018 Intel Corporation
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*/
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#include <linux/mutex.h>
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#include "i915_drv.h"
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#include "i915_globals.h"
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#include "i915_request.h"
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#include "i915_scheduler.h"
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static struct i915_global_scheduler {
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struct i915_global base;
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struct kmem_cache *slab_dependencies;
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struct kmem_cache *slab_priorities;
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} global;
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static DEFINE_SPINLOCK(schedule_lock);
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static const struct i915_request *
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node_to_request(const struct i915_sched_node *node)
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{
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return container_of(node, const struct i915_request, sched);
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}
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static inline bool node_started(const struct i915_sched_node *node)
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{
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return i915_request_started(node_to_request(node));
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}
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static inline bool node_signaled(const struct i915_sched_node *node)
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{
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return i915_request_completed(node_to_request(node));
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}
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static inline struct i915_priolist *to_priolist(struct rb_node *rb)
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{
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return rb_entry(rb, struct i915_priolist, node);
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}
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static void assert_priolists(struct intel_engine_execlists * const execlists)
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{
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struct rb_node *rb;
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long last_prio, i;
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if (!IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
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return;
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GEM_BUG_ON(rb_first_cached(&execlists->queue) !=
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rb_first(&execlists->queue.rb_root));
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last_prio = (INT_MAX >> I915_USER_PRIORITY_SHIFT) + 1;
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for (rb = rb_first_cached(&execlists->queue); rb; rb = rb_next(rb)) {
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const struct i915_priolist *p = to_priolist(rb);
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GEM_BUG_ON(p->priority >= last_prio);
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last_prio = p->priority;
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GEM_BUG_ON(!p->used);
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for (i = 0; i < ARRAY_SIZE(p->requests); i++) {
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if (list_empty(&p->requests[i]))
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continue;
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GEM_BUG_ON(!(p->used & BIT(i)));
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}
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}
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}
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struct list_head *
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i915_sched_lookup_priolist(struct intel_engine_cs *engine, int prio)
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{
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struct intel_engine_execlists * const execlists = &engine->execlists;
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struct i915_priolist *p;
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struct rb_node **parent, *rb;
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bool first = true;
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int idx, i;
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lockdep_assert_held(&engine->active.lock);
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assert_priolists(execlists);
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/* buckets sorted from highest [in slot 0] to lowest priority */
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idx = I915_PRIORITY_COUNT - (prio & I915_PRIORITY_MASK) - 1;
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prio >>= I915_USER_PRIORITY_SHIFT;
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if (unlikely(execlists->no_priolist))
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prio = I915_PRIORITY_NORMAL;
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find_priolist:
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/* most positive priority is scheduled first, equal priorities fifo */
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rb = NULL;
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parent = &execlists->queue.rb_root.rb_node;
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while (*parent) {
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rb = *parent;
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p = to_priolist(rb);
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if (prio > p->priority) {
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parent = &rb->rb_left;
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} else if (prio < p->priority) {
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parent = &rb->rb_right;
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first = false;
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} else {
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goto out;
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}
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}
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if (prio == I915_PRIORITY_NORMAL) {
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p = &execlists->default_priolist;
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} else {
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p = kmem_cache_alloc(global.slab_priorities, GFP_ATOMIC);
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/* Convert an allocation failure to a priority bump */
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if (unlikely(!p)) {
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prio = I915_PRIORITY_NORMAL; /* recurses just once */
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/* To maintain ordering with all rendering, after an
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* allocation failure we have to disable all scheduling.
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* Requests will then be executed in fifo, and schedule
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* will ensure that dependencies are emitted in fifo.
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* There will be still some reordering with existing
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* requests, so if userspace lied about their
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* dependencies that reordering may be visible.
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*/
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execlists->no_priolist = true;
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goto find_priolist;
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}
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}
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p->priority = prio;
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for (i = 0; i < ARRAY_SIZE(p->requests); i++)
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INIT_LIST_HEAD(&p->requests[i]);
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rb_link_node(&p->node, rb, parent);
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rb_insert_color_cached(&p->node, &execlists->queue, first);
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p->used = 0;
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out:
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p->used |= BIT(idx);
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return &p->requests[idx];
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}
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void __i915_priolist_free(struct i915_priolist *p)
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{
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kmem_cache_free(global.slab_priorities, p);
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}
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struct sched_cache {
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struct list_head *priolist;
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};
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static struct intel_engine_cs *
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sched_lock_engine(const struct i915_sched_node *node,
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struct intel_engine_cs *locked,
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struct sched_cache *cache)
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{
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const struct i915_request *rq = node_to_request(node);
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struct intel_engine_cs *engine;
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GEM_BUG_ON(!locked);
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/*
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* Virtual engines complicate acquiring the engine timeline lock,
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* as their rq->engine pointer is not stable until under that
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* engine lock. The simple ploy we use is to take the lock then
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* check that the rq still belongs to the newly locked engine.
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*/
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while (locked != (engine = READ_ONCE(rq->engine))) {
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spin_unlock(&locked->active.lock);
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memset(cache, 0, sizeof(*cache));
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spin_lock(&engine->active.lock);
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locked = engine;
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}
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GEM_BUG_ON(locked != engine);
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return locked;
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}
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static inline int rq_prio(const struct i915_request *rq)
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{
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return rq->sched.attr.priority | __NO_PREEMPTION;
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}
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static void kick_submission(struct intel_engine_cs *engine, int prio)
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{
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const struct i915_request *inflight =
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port_request(engine->execlists.port);
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/*
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* If we are already the currently executing context, don't
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* bother evaluating if we should preempt ourselves, or if
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* we expect nothing to change as a result of running the
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* tasklet, i.e. we have not change the priority queue
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* sufficiently to oust the running context.
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*/
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if (!inflight || !i915_scheduler_need_preempt(prio, rq_prio(inflight)))
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return;
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tasklet_hi_schedule(&engine->execlists.tasklet);
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}
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static void __i915_schedule(struct i915_sched_node *node,
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const struct i915_sched_attr *attr)
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{
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struct intel_engine_cs *engine;
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struct i915_dependency *dep, *p;
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struct i915_dependency stack;
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const int prio = attr->priority;
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struct sched_cache cache;
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LIST_HEAD(dfs);
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/* Needed in order to use the temporary link inside i915_dependency */
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lockdep_assert_held(&schedule_lock);
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GEM_BUG_ON(prio == I915_PRIORITY_INVALID);
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if (prio <= READ_ONCE(node->attr.priority))
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return;
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if (node_signaled(node))
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return;
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stack.signaler = node;
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list_add(&stack.dfs_link, &dfs);
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/*
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* Recursively bump all dependent priorities to match the new request.
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*
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* A naive approach would be to use recursion:
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* static void update_priorities(struct i915_sched_node *node, prio) {
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* list_for_each_entry(dep, &node->signalers_list, signal_link)
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* update_priorities(dep->signal, prio)
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* queue_request(node);
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* }
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* but that may have unlimited recursion depth and so runs a very
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* real risk of overunning the kernel stack. Instead, we build
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* a flat list of all dependencies starting with the current request.
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* As we walk the list of dependencies, we add all of its dependencies
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* to the end of the list (this may include an already visited
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* request) and continue to walk onwards onto the new dependencies. The
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* end result is a topological list of requests in reverse order, the
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* last element in the list is the request we must execute first.
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*/
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list_for_each_entry(dep, &dfs, dfs_link) {
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struct i915_sched_node *node = dep->signaler;
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/* If we are already flying, we know we have no signalers */
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if (node_started(node))
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continue;
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/*
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* Within an engine, there can be no cycle, but we may
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* refer to the same dependency chain multiple times
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* (redundant dependencies are not eliminated) and across
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* engines.
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*/
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list_for_each_entry(p, &node->signalers_list, signal_link) {
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GEM_BUG_ON(p == dep); /* no cycles! */
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if (node_signaled(p->signaler))
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continue;
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if (prio > READ_ONCE(p->signaler->attr.priority))
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list_move_tail(&p->dfs_link, &dfs);
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}
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}
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/*
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* If we didn't need to bump any existing priorities, and we haven't
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* yet submitted this request (i.e. there is no potential race with
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* execlists_submit_request()), we can set our own priority and skip
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* acquiring the engine locks.
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*/
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if (node->attr.priority == I915_PRIORITY_INVALID) {
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GEM_BUG_ON(!list_empty(&node->link));
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node->attr = *attr;
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if (stack.dfs_link.next == stack.dfs_link.prev)
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return;
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__list_del_entry(&stack.dfs_link);
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}
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memset(&cache, 0, sizeof(cache));
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engine = node_to_request(node)->engine;
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spin_lock(&engine->active.lock);
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/* Fifo and depth-first replacement ensure our deps execute before us */
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engine = sched_lock_engine(node, engine, &cache);
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list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) {
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INIT_LIST_HEAD(&dep->dfs_link);
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node = dep->signaler;
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engine = sched_lock_engine(node, engine, &cache);
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lockdep_assert_held(&engine->active.lock);
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/* Recheck after acquiring the engine->timeline.lock */
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if (prio <= node->attr.priority || node_signaled(node))
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continue;
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GEM_BUG_ON(node_to_request(node)->engine != engine);
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node->attr.priority = prio;
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if (list_empty(&node->link)) {
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/*
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* If the request is not in the priolist queue because
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* it is not yet runnable, then it doesn't contribute
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* to our preemption decisions. On the other hand,
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* if the request is on the HW, it too is not in the
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* queue; but in that case we may still need to reorder
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* the inflight requests.
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*/
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continue;
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}
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if (!intel_engine_is_virtual(engine) &&
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!i915_request_is_active(node_to_request(node))) {
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if (!cache.priolist)
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cache.priolist =
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i915_sched_lookup_priolist(engine,
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prio);
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list_move_tail(&node->link, cache.priolist);
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}
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if (prio <= engine->execlists.queue_priority_hint)
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continue;
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engine->execlists.queue_priority_hint = prio;
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/* Defer (tasklet) submission until after all of our updates. */
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kick_submission(engine, prio);
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}
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spin_unlock(&engine->active.lock);
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}
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void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr)
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{
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spin_lock_irq(&schedule_lock);
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__i915_schedule(&rq->sched, attr);
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spin_unlock_irq(&schedule_lock);
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}
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static void __bump_priority(struct i915_sched_node *node, unsigned int bump)
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{
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struct i915_sched_attr attr = node->attr;
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attr.priority |= bump;
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__i915_schedule(node, &attr);
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}
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void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump)
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{
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unsigned long flags;
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GEM_BUG_ON(bump & ~I915_PRIORITY_MASK);
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if (READ_ONCE(rq->sched.attr.priority) == I915_PRIORITY_INVALID)
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return;
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spin_lock_irqsave(&schedule_lock, flags);
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__bump_priority(&rq->sched, bump);
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spin_unlock_irqrestore(&schedule_lock, flags);
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}
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void i915_sched_node_init(struct i915_sched_node *node)
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{
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INIT_LIST_HEAD(&node->signalers_list);
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INIT_LIST_HEAD(&node->waiters_list);
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INIT_LIST_HEAD(&node->link);
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node->attr.priority = I915_PRIORITY_INVALID;
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node->semaphores = 0;
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node->flags = 0;
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}
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static struct i915_dependency *
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i915_dependency_alloc(void)
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{
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return kmem_cache_alloc(global.slab_dependencies, GFP_KERNEL);
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}
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static void
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i915_dependency_free(struct i915_dependency *dep)
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{
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kmem_cache_free(global.slab_dependencies, dep);
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}
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bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
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struct i915_sched_node *signal,
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struct i915_dependency *dep,
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unsigned long flags)
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{
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bool ret = false;
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spin_lock_irq(&schedule_lock);
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if (!node_signaled(signal)) {
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INIT_LIST_HEAD(&dep->dfs_link);
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list_add(&dep->wait_link, &signal->waiters_list);
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list_add(&dep->signal_link, &node->signalers_list);
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dep->signaler = signal;
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dep->flags = flags;
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/* Keep track of whether anyone on this chain has a semaphore */
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if (signal->flags & I915_SCHED_HAS_SEMAPHORE_CHAIN &&
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!node_started(signal))
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node->flags |= I915_SCHED_HAS_SEMAPHORE_CHAIN;
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/*
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* As we do not allow WAIT to preempt inflight requests,
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* once we have executed a request, along with triggering
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* any execution callbacks, we must preserve its ordering
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* within the non-preemptible FIFO.
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*/
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BUILD_BUG_ON(__NO_PREEMPTION & ~I915_PRIORITY_MASK);
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if (flags & I915_DEPENDENCY_EXTERNAL)
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__bump_priority(signal, __NO_PREEMPTION);
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ret = true;
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}
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spin_unlock_irq(&schedule_lock);
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return ret;
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}
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int i915_sched_node_add_dependency(struct i915_sched_node *node,
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struct i915_sched_node *signal)
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{
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struct i915_dependency *dep;
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dep = i915_dependency_alloc();
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if (!dep)
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return -ENOMEM;
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if (!__i915_sched_node_add_dependency(node, signal, dep,
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I915_DEPENDENCY_EXTERNAL |
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I915_DEPENDENCY_ALLOC))
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i915_dependency_free(dep);
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return 0;
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}
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void i915_sched_node_fini(struct i915_sched_node *node)
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{
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struct i915_dependency *dep, *tmp;
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spin_lock_irq(&schedule_lock);
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/*
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* Everyone we depended upon (the fences we wait to be signaled)
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* should retire before us and remove themselves from our list.
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* However, retirement is run independently on each timeline and
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* so we may be called out-of-order.
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*/
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list_for_each_entry_safe(dep, tmp, &node->signalers_list, signal_link) {
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GEM_BUG_ON(!node_signaled(dep->signaler));
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GEM_BUG_ON(!list_empty(&dep->dfs_link));
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list_del(&dep->wait_link);
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if (dep->flags & I915_DEPENDENCY_ALLOC)
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i915_dependency_free(dep);
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}
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/* Remove ourselves from everyone who depends upon us */
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list_for_each_entry_safe(dep, tmp, &node->waiters_list, wait_link) {
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GEM_BUG_ON(dep->signaler != node);
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GEM_BUG_ON(!list_empty(&dep->dfs_link));
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list_del(&dep->signal_link);
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if (dep->flags & I915_DEPENDENCY_ALLOC)
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i915_dependency_free(dep);
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}
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spin_unlock_irq(&schedule_lock);
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}
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static void i915_global_scheduler_shrink(void)
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{
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kmem_cache_shrink(global.slab_dependencies);
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kmem_cache_shrink(global.slab_priorities);
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}
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static void i915_global_scheduler_exit(void)
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{
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kmem_cache_destroy(global.slab_dependencies);
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kmem_cache_destroy(global.slab_priorities);
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}
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static struct i915_global_scheduler global = { {
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.shrink = i915_global_scheduler_shrink,
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.exit = i915_global_scheduler_exit,
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} };
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int __init i915_global_scheduler_init(void)
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{
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global.slab_dependencies = KMEM_CACHE(i915_dependency,
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SLAB_HWCACHE_ALIGN);
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if (!global.slab_dependencies)
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return -ENOMEM;
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global.slab_priorities = KMEM_CACHE(i915_priolist,
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SLAB_HWCACHE_ALIGN);
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if (!global.slab_priorities)
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goto err_priorities;
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i915_global_register(&global.base);
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|
return 0;
|
|
|
|
err_priorities:
|
|
kmem_cache_destroy(global.slab_priorities);
|
|
return -ENOMEM;
|
|
}
|