From patchwork Thu Jul 25 22:44:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11059923 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C5E376C5 for ; Thu, 25 Jul 2019 22:44:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B4A9628A71 for ; Thu, 25 Jul 2019 22:44:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A8BC628A74; Thu, 25 Jul 2019 22:44:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 3EC9F28A71 for ; Thu, 25 Jul 2019 22:44:34 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C49876E83B; Thu, 25 Jul 2019 22:44:33 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id F30016E83A for ; Thu, 25 Jul 2019 22:44:28 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 17610923-1500050 for multiple; Thu, 25 Jul 2019 23:44:09 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Thu, 25 Jul 2019 23:44:06 +0100 Message-Id: <20190725224407.4206-4-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190725224407.4206-1-chris@chris-wilson.co.uk> References: <20190725224407.4206-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 4/5] drm/i915/execlists: Force preemption X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP If the preempted context takes too long to relinquish control, e.g. it is stuck inside a shader with arbitration disabled, evict that context with an engine reset. This ensures that preemptions are reasonably responsive, providing a tighter QoS for the more important context at the cost of flagging unresponsive contexts more frequently (i.e. instead of using an ~10s hangcheck, we now evict at ~100ms). The challenge of lies in picking a timeout that can be reasonably serviced by HW for typical workloads, balancing the existing clients against the needs for responsiveness. Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Tvrtko Ursulin Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/Kconfig.profile | 12 ++++++ drivers/gpu/drm/i915/gt/intel_lrc.c | 62 ++++++++++++++++++++++++++-- 2 files changed, 71 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile index 48df8889a88a..3184e8491333 100644 --- a/drivers/gpu/drm/i915/Kconfig.profile +++ b/drivers/gpu/drm/i915/Kconfig.profile @@ -25,3 +25,15 @@ config DRM_I915_SPIN_REQUEST May be 0 to disable the initial spin. In practice, we estimate the cost of enabling the interrupt (if currently disabled) to be a few microseconds. + +config DRM_I915_PREEMPT_TIMEOUT + int "Preempt timeout (ms)" + default 100 # milliseconds + help + How long to wait (in milliseconds) for a preemption event to occur + when submitting a new context via execlists. If the current context + does not hit an arbitration point and yield to HW before the timer + expires, the HW will be reset to allow the more important context + to execute. + + May be 0 to disable the timeout. diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index 884dfc1cb033..b85ee12c2451 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -945,6 +945,21 @@ static void record_preemption(struct intel_engine_execlists *execlists) (void)I915_SELFTEST_ONLY(execlists->preempt_hang.count++); } +static unsigned long preempt_expires(void) +{ + const unsigned long timeout = + msecs_to_jiffies_timeout(CONFIG_DRM_I915_PREEMPT_TIMEOUT); + + /* + * Paranoia to make sure the compiler computes the timeout before + * loading 'jiffies' as jiffies is volatile and may be updated in + * the background by a timer tick. All to reduce the complexity + * of the addition and reduce the risk of losing a jiffie. + */ + barrier(); + return jiffies + timeout; +} + static void execlists_dequeue(struct intel_engine_cs *engine) { struct intel_engine_execlists * const execlists = &engine->execlists; @@ -1283,6 +1298,8 @@ static void execlists_dequeue(struct intel_engine_cs *engine) *port = execlists_schedule_in(last, port - execlists->pending); memset(port + 1, 0, (last_port - port) * sizeof(*port)); execlists_submit_ports(engine); + if (CONFIG_DRM_I915_PREEMPT_TIMEOUT) + mod_timer(&execlists->timer, preempt_expires()); } else { ring_set_paused(engine, 0); } @@ -1467,13 +1484,45 @@ static void process_csb(struct intel_engine_cs *engine) invalidate_csb_entries(&buf[0], &buf[num_entries - 1]); } -static void __execlists_submission_tasklet(struct intel_engine_cs *const engine) +static bool __execlists_submission_tasklet(struct intel_engine_cs *const engine) { lockdep_assert_held(&engine->active.lock); process_csb(engine); - if (!engine->execlists.pending[0]) + if (!engine->execlists.pending[0]) { execlists_dequeue(engine); + return true; + } + + return false; +} + +static void preempt_reset(struct intel_engine_cs *engine) +{ + const unsigned int bit = I915_RESET_ENGINE + engine->id; + unsigned long *lock = &engine->gt->reset.flags; + + if (test_and_set_bit(bit, lock)) + return; + + /* Mark this tasklet as disabled to avoid waiting for it to complete */ + tasklet_disable_nosync(&engine->execlists.tasklet); + + intel_engine_reset(engine, "preemption time out"); + + tasklet_enable(&engine->execlists.tasklet); + clear_and_wake_up_bit(bit, lock); +} + +static bool preempt_timeout(struct intel_engine_cs *const engine) +{ + if (!CONFIG_DRM_I915_PREEMPT_TIMEOUT) + return false; + + if (!intel_engine_has_preemption(engine)) + return false; + + return !timer_pending(&engine->execlists.timer); } /* @@ -1484,10 +1533,17 @@ static void execlists_submission_tasklet(unsigned long data) { struct intel_engine_cs * const engine = (struct intel_engine_cs *)data; unsigned long flags; + bool reset = false; spin_lock_irqsave(&engine->active.lock, flags); - __execlists_submission_tasklet(engine); + + if (!__execlists_submission_tasklet(engine) && preempt_timeout(engine)) + reset = true; + spin_unlock_irqrestore(&engine->active.lock, flags); + + if (reset) + preempt_reset(engine); } static void execlists_submission_timer(struct timer_list *timer)