From patchwork Wed May 27 13:02:14 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11572953 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 72C8660D for ; Wed, 27 May 2020 13:02:47 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 56C1820873 for ; Wed, 27 May 2020 13:02:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56C1820873 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4808C6E14D; Wed, 27 May 2020 13:02:45 +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 D98236E09E for ; Wed, 27 May 2020 13:02:43 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from build.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 21309449-1500050 for multiple; Wed, 27 May 2020 14:02:15 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Wed, 27 May 2020 14:02:14 +0100 Message-Id: <20200527130214.1239-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH] drm/i915/gt: Prevent timeslicing into unpreemptible requests X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Chris Wilson Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" We have a I915_REQUEST_NOPREEMPT flag that we set when we must prevent the HW from preempting during the course of this request. We need to honour this flag and protect the HW even if we have a heartbeat request, or other maximum priority barrier, pending. As such, restrict the timeslicing check to avoid preempting into the topmost priority band, leaving the unpreemptable requests in blissful peace running uninterrupted on the HW. Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin --- drivers/gpu/drm/i915/gt/intel_lrc.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index a8fdd4f9eb5a..cf63613c2a60 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -1896,6 +1896,15 @@ static void defer_active(struct intel_engine_cs *engine) defer_request(rq, i915_sched_lookup_priolist(engine, rq_prio(rq))); } +static inline int never_timeslice(int prio) +{ + /* Don't allow timeslicing of the 'unpreemptible' requests */ + if (prio == I915_PRIORITY_UNPREEMPTABLE) + prio--; + + return prio; +} + static bool need_timeslice(const struct intel_engine_cs *engine, const struct i915_request *rq, @@ -1927,6 +1936,7 @@ need_timeslice(const struct intel_engine_cs *engine, if (!list_is_last(&rq->sched.link, &engine->active.requests)) hint = max(hint, rq_prio(list_next_entry(rq, sched.link))); + hint = never_timeslice(hint); return hint >= effective_prio(rq); } @@ -2007,6 +2017,7 @@ static void start_timeslice(struct intel_engine_cs *engine, int prio) if (!intel_engine_has_timeslices(engine)) return; + prio = never_timeslice(prio); WRITE_ONCE(execlists->switch_priority_hint, prio); if (prio == INT_MIN) return;