From mboxrd@z Thu Jan 1 00:00:00 1970 From: oscar.mateo@intel.com Subject: [PATCH 41/53] drm/i915/bdw: Avoid non-lite-restore preemptions Date: Fri, 13 Jun 2014 16:37:59 +0100 Message-ID: <1402673891-14618-42-git-send-email-oscar.mateo@intel.com> References: <1402673891-14618-1-git-send-email-oscar.mateo@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTP id 0E83C6EA7E for ; Fri, 13 Jun 2014 08:43:34 -0700 (PDT) In-Reply-To: <1402673891-14618-1-git-send-email-oscar.mateo@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org From: Oscar Mateo In the current Execlists feeding mechanism, full preemption is not supported yet: only lite-restores are allowed (this is: the GPU simply samples a new tail pointer for the context currently in execution). But we have identified an scenario in which a full preemption occurs: 1) We submit two contexts for execution (A & B). 2) The GPU finishes with the first one (A), switches to the second one (B) and informs us. 3) We submit B again (hoping to cause a lite restore) together with C, but in the time we spend writing to the ELSP, the GPU finishes B. 4) The GPU start executing B again (since we told it so). 5) We receive a B finished interrupt and, mistakenly, we submit C (again) and D, causing a full preemption of B. By keeping a better track of our submissions, we can avoid the scenario described above. v2: elsp_submitted belongs in the new intel_ctx_submit_request. Several rebase changes. Signed-off-by: Oscar Mateo --- drivers/gpu/drm/i915/intel_lrc.c | 28 ++++++++++++++++++++++++---- drivers/gpu/drm/i915/intel_lrc.h | 2 ++ 2 files changed, 26 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 290391c..f388b28 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -248,6 +248,7 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring) else if (req0->ctx == cursor->ctx) { /* Same ctx: ignore first request, as second request * will update tail past first request's workload */ + cursor->elsp_submitted = req0->elsp_submitted; list_del(&req0->execlist_link); queue_work(dev_priv->wq, &req0->work); req0 = cursor; @@ -257,8 +258,14 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring) } } + WARN_ON(req1 && req1->elsp_submitted); + BUG_ON(execlists_submit_context(ring, req0->ctx, req0->tail, req1? req1->ctx : NULL, req1? req1->tail : 0)); + + req0->elsp_submitted++; + if (req1) + req1->elsp_submitted++; } static bool execlists_check_remove_request(struct intel_engine_cs *ring, @@ -275,9 +282,13 @@ static bool execlists_check_remove_request(struct intel_engine_cs *ring, struct drm_i915_gem_object *ctx_obj = head_req->ctx->engine[ring->id].obj; if (intel_execlists_ctx_id(ctx_obj) == request_id) { - list_del(&head_req->execlist_link); - queue_work(dev_priv->wq, &head_req->work); - return true; + WARN(head_req->elsp_submitted == 0, + "Never submitted head request\n"); + if (--head_req->elsp_submitted <= 0) { + list_del(&head_req->execlist_link); + queue_work(dev_priv->wq, &head_req->work); + return true; + } } } @@ -310,7 +321,16 @@ void intel_execlists_handle_ctx_events(struct intel_engine_cs *ring) status_id = I915_READ(RING_CONTEXT_STATUS_BUF(ring) + (read_pointer % 6) * 8 + 4); - if (status & GEN8_CTX_STATUS_COMPLETE) { + if (status & GEN8_CTX_STATUS_PREEMPTED) { + if (status & GEN8_CTX_STATUS_LITE_RESTORE) { + if (execlists_check_remove_request(ring, status_id)) + WARN(1, "Lite Restored request removed from queue\n"); + } else + WARN(1, "Preemption without Lite Restore\n"); + } + + if ((status & GEN8_CTX_STATUS_ACTIVE_IDLE) || + (status & GEN8_CTX_STATUS_ELEMENT_SWITCH)) { if (execlists_check_remove_request(ring, status_id)) submit_contexts++; } diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h index 7949dff..ee877aa 100644 --- a/drivers/gpu/drm/i915/intel_lrc.h +++ b/drivers/gpu/drm/i915/intel_lrc.h @@ -51,6 +51,8 @@ struct intel_ctx_submit_request { struct list_head execlist_link; struct work_struct work; + + int elsp_submitted; }; void intel_execlists_handle_ctx_events(struct intel_engine_cs *ring); -- 1.9.0