drm/i915: Keep a per-engine request pool
Add a tiny per-engine request mempool so that we should always have a request available for powermanagement allocations from tricky contexts. This reserve is expected to be only used for kernel contexts when barriers must be emitted [almost] without fail. The main consumer for this reserved request is expected to be engine-pm, for which we know that there will always be at least the previous pm request that we can reuse under mempressure (so there should always be a spare request for engine_park()). This is an alternative to using a comparatively bulky mempool, which requires custom handling for both our reserved allocation requirement and to protect our TYPESAFE_BY_RCU slab cache. The advantage of mempool would be that it would allow us to keep a larger per-engine request pool. However, converting over to mempool is straightforward should the need arise. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Reviewed-and-tested-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200402184037.21630-1-chris@chris-wilson.co.uk
This commit is contained in:
parent
63d0f3ea8e
commit
43acd6516c
|
@ -431,7 +431,14 @@ void intel_engines_free(struct intel_gt *gt)
|
|||
struct intel_engine_cs *engine;
|
||||
enum intel_engine_id id;
|
||||
|
||||
/* Free the requests! dma-resv keeps fences around for an eternity */
|
||||
rcu_barrier();
|
||||
|
||||
for_each_engine(engine, gt, id) {
|
||||
if (engine->request_pool)
|
||||
kmem_cache_free(i915_request_slab_cache(),
|
||||
engine->request_pool);
|
||||
|
||||
kfree(engine);
|
||||
gt->engine[id] = NULL;
|
||||
}
|
||||
|
|
|
@ -308,6 +308,9 @@ struct intel_engine_cs {
|
|||
struct list_head hold; /* ready requests, but on hold */
|
||||
} active;
|
||||
|
||||
/* keep a request in reserve for a [pm] barrier under oom */
|
||||
struct i915_request *request_pool;
|
||||
|
||||
struct llist_head barrier_tasks;
|
||||
|
||||
struct intel_context *kernel_context; /* pinned */
|
||||
|
|
|
@ -101,6 +101,11 @@ static signed long i915_fence_wait(struct dma_fence *fence,
|
|||
timeout);
|
||||
}
|
||||
|
||||
struct kmem_cache *i915_request_slab_cache(void)
|
||||
{
|
||||
return global.slab_requests;
|
||||
}
|
||||
|
||||
static void i915_fence_release(struct dma_fence *fence)
|
||||
{
|
||||
struct i915_request *rq = to_request(fence);
|
||||
|
@ -115,6 +120,10 @@ static void i915_fence_release(struct dma_fence *fence)
|
|||
i915_sw_fence_fini(&rq->submit);
|
||||
i915_sw_fence_fini(&rq->semaphore);
|
||||
|
||||
/* Keep one request on each engine for reserved use under mempressure */
|
||||
if (!cmpxchg(&rq->engine->request_pool, NULL, rq))
|
||||
return;
|
||||
|
||||
kmem_cache_free(global.slab_requests, rq);
|
||||
}
|
||||
|
||||
|
@ -629,14 +638,22 @@ static void retire_requests(struct intel_timeline *tl)
|
|||
}
|
||||
|
||||
static noinline struct i915_request *
|
||||
request_alloc_slow(struct intel_timeline *tl, gfp_t gfp)
|
||||
request_alloc_slow(struct intel_timeline *tl,
|
||||
struct i915_request **rsvd,
|
||||
gfp_t gfp)
|
||||
{
|
||||
struct i915_request *rq;
|
||||
|
||||
if (list_empty(&tl->requests))
|
||||
goto out;
|
||||
/* If we cannot wait, dip into our reserves */
|
||||
if (!gfpflags_allow_blocking(gfp)) {
|
||||
rq = xchg(rsvd, NULL);
|
||||
if (!rq) /* Use the normal failure path for one final WARN */
|
||||
goto out;
|
||||
|
||||
if (!gfpflags_allow_blocking(gfp))
|
||||
return rq;
|
||||
}
|
||||
|
||||
if (list_empty(&tl->requests))
|
||||
goto out;
|
||||
|
||||
/* Move our oldest request to the slab-cache (if not in use!) */
|
||||
|
@ -721,7 +738,7 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
|
|||
rq = kmem_cache_alloc(global.slab_requests,
|
||||
gfp | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
|
||||
if (unlikely(!rq)) {
|
||||
rq = request_alloc_slow(tl, gfp);
|
||||
rq = request_alloc_slow(tl, &ce->engine->request_pool, gfp);
|
||||
if (!rq) {
|
||||
ret = -ENOMEM;
|
||||
goto err_unreserve;
|
||||
|
|
|
@ -300,6 +300,8 @@ static inline bool dma_fence_is_i915(const struct dma_fence *fence)
|
|||
return fence->ops == &i915_fence_ops;
|
||||
}
|
||||
|
||||
struct kmem_cache *i915_request_slab_cache(void);
|
||||
|
||||
struct i915_request * __must_check
|
||||
__i915_request_create(struct intel_context *ce, gfp_t gfp);
|
||||
struct i915_request * __must_check
|
||||
|
|
Loading…
Reference in New Issue