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drm/i915: Stop tracking timeline->inflight_seqnos 

In commit 9b6586ae9f ("drm/i915: Keep a global seqno per-engine"), we
moved from a global inflight counter to per-engine counters in the
hope that will be easy to run concurrently in future. However, with the
advent of the desire to move requests between engines, we do need a
global counter to preserve the semantics that no engine wraps in the
middle of a submit. (Although this semantic is now only required for gen7
semaphore support, which only supports greater-then comparisons!)

v2: Keep a global counter of all requests ever submitted and force the
reset when it wraps.

References: 9b6586ae9f ("drm/i915: Keep a global seqno per-engine")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180430131503.5375-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2018-04-30 14:15:00 +01:00
parent 5692251c25
commit 52d7f16e55
5 changed files with 22 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/gpu/drm/i915/i915_debugfs.c
View File

@ -1340,10 +1340,9 @@ static int i915_hangcheck_info(struct seq_file *m, void *unused)
struct rb_node *rb;
seq_printf(m, "%s:\n", engine->name);
seq_printf(m, "\tseqno = %x [current %x, last %x], inflight %d\n",
seq_printf(m, "\tseqno = %x [current %x, last %x]\n",
engine->hangcheck.seqno, seqno[id],
intel_engine_last_submit(engine),
engine->timeline->inflight_seqnos);
intel_engine_last_submit(engine));
seq_printf(m, "\twaiters? %s, fake irq active? %s, stalled? %s\n",
yesno(intel_engine_has_waiter(engine)),
yesno(test_bit(engine->id,

1
drivers/gpu/drm/i915/i915_drv.h
View File

@ -2062,6 +2062,7 @@ struct drm_i915_private {
struct list_head timelines;
struct i915_gem_timeline global_timeline;
u32 active_requests;
u32 request_serial;
/**
* Is the GPU currently considered idle, or busy executing

6
drivers/gpu/drm/i915/i915_gem_timeline.h
View File

@ -37,12 +37,6 @@ struct intel_timeline {
u64 fence_context;
u32 seqno;
/**
* Count of outstanding requests, from the time they are constructed
* to the moment they are retired. Loosely coupled to hardware.
*/
u32 inflight_seqnos;
spinlock_t lock;
/**

33
drivers/gpu/drm/i915/i915_request.c
View File

@ -241,6 +241,7 @@ static int reset_all_global_seqno(struct drm_i915_private *i915, u32 seqno)
sizeof(timeline->engine[id].global_sync));
}
i915->gt.request_serial = seqno;
return 0;
}
@ -257,18 +258,22 @@ int i915_gem_set_global_seqno(struct drm_device *dev, u32 seqno)
return reset_all_global_seqno(i915, seqno - 1);
}
static int reserve_engine(struct intel_engine_cs *engine)
static int reserve_gt(struct drm_i915_private *i915)
{
struct drm_i915_private *i915 = engine->i915;
u32 active = ++engine->timeline->inflight_seqnos;
u32 seqno = engine->timeline->seqno;
int ret;
/* Reservation is fine until we need to wrap around */
if (unlikely(add_overflows(seqno, active))) {
/*
* Reservation is fine until we may need to wrap around
*
* By incrementing the serial for every request, we know that no
* individual engine may exceed that serial (as each is reset to 0
* on any wrap). This protects even the most pessimistic of migrations
* of every request from all engines onto just one.
*/
while (unlikely(++i915->gt.request_serial == 0)) {
ret = reset_all_global_seqno(i915, 0);
if (ret) {
engine->timeline->inflight_seqnos--;
i915->gt.request_serial--;
return ret;
}
}
@ -279,15 +284,10 @@ static int reserve_engine(struct intel_engine_cs *engine)
return 0;
}
static void unreserve_engine(struct intel_engine_cs *engine)
static void unreserve_gt(struct drm_i915_private *i915)
{
struct drm_i915_private *i915 = engine->i915;
if (!--i915->gt.active_requests)
i915_gem_park(i915);
GEM_BUG_ON(!engine->timeline->inflight_seqnos);
engine->timeline->inflight_seqnos--;
}
void i915_gem_retire_noop(struct i915_gem_active *active,
@ -362,7 +362,6 @@ static void i915_request_retire(struct i915_request *request)
list_del_init(&request->link);
spin_unlock_irq(&engine->timeline->lock);
unreserve_engine(request->engine);
advance_ring(request);
free_capture_list(request);
@ -424,6 +423,8 @@ static void i915_request_retire(struct i915_request *request)
}
spin_unlock_irq(&request->lock);
unreserve_gt(request->i915);
i915_sched_node_fini(request->i915, &request->sched);
i915_request_put(request);
}
@ -642,7 +643,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
return ERR_CAST(ring);
GEM_BUG_ON(!ring);
ret = reserve_engine(engine);
ret = reserve_gt(i915);
if (ret)
goto err_unpin;
@ -784,7 +785,7 @@ err_unwind:
kmem_cache_free(i915->requests, rq);
err_unreserve:
unreserve_engine(engine);
unreserve_gt(i915);
err_unpin:
engine->context_unpin(engine, ctx);
return ERR_PTR(ret);

5
drivers/gpu/drm/i915/intel_engine_cs.c
View File

@ -1321,12 +1321,11 @@ void intel_engine_dump(struct intel_engine_cs *engine,
if (i915_terminally_wedged(&engine->i915->gpu_error))
drm_printf(m, "*** WEDGED ***\n");
drm_printf(m, "\tcurrent seqno %x, last %x, hangcheck %x [%d ms], inflight %d\n",
drm_printf(m, "\tcurrent seqno %x, last %x, hangcheck %x [%d ms]\n",
intel_engine_get_seqno(engine),
intel_engine_last_submit(engine),
engine->hangcheck.seqno,
jiffies_to_msecs(jiffies - engine->hangcheck.action_timestamp),
engine->timeline->inflight_seqnos);
jiffies_to_msecs(jiffies - engine->hangcheck.action_timestamp));
drm_printf(m, "\tReset count: %d (global %d)\n",
i915_reset_engine_count(error, engine),
i915_reset_count(error));