From patchwork Thu Nov 26 14:04:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 11934131 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27786C63697 for ; Thu, 26 Nov 2020 14:04:21 +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 B74952075A for ; Thu, 26 Nov 2020 14:04:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B74952075A 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 AEB356E973; Thu, 26 Nov 2020 14:04:19 +0000 (UTC) Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6D7BB6E973 for ; Thu, 26 Nov 2020 14:04:13 +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 23117560-1500050 for ; Thu, 26 Nov 2020 14:04:08 +0000 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Thu, 26 Nov 2020 14:04:04 +0000 Message-Id: <20201126140407.31952-2-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201126140407.31952-1-chris@chris-wilson.co.uk> References: <20201126140407.31952-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Subject: [Intel-gfx] [CI 2/5] drm/i915/gt: Check for a completed last request once 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: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Pull the repeated check for the last active request being completed to a single spot, when deciding whether or not execlist preemption is required. In doing so, we remove the tasklet kick, introduced with the completion checks in commit 35f3fd8182ba ("drm/i915/execlists: Workaround switching back to a completed context"), if we find the request was completed but have not yet seen the corresponding CS event. This was devolving into a busy spin of the tasklet while we waited for the event as the delivery was not as instantaneous as expected. Under load this is sufficient to exhaust the tasklet softirq timeslice, and force ksoftirqd. Quite noticeable overhead for no apparent improvement in latency. Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/gt/intel_lrc.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c index cf11cbac241b..43703efb36d1 100644 --- a/drivers/gpu/drm/i915/gt/intel_lrc.c +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c @@ -2141,12 +2141,9 @@ static void execlists_dequeue(struct intel_engine_cs *engine) */ if ((last = *active)) { - if (need_preempt(engine, last, rb)) { - if (i915_request_completed(last)) { - tasklet_hi_schedule(&execlists->tasklet); - return; - } - + if (i915_request_completed(last)) { + goto check_secondary; + } else if (need_preempt(engine, last, rb)) { ENGINE_TRACE(engine, "preempting last=%llx:%lld, prio=%d, hint=%d\n", last->fence.context, @@ -2174,11 +2171,6 @@ static void execlists_dequeue(struct intel_engine_cs *engine) last = NULL; } else if (need_timeslice(engine, last, rb) && timeslice_expired(execlists, last)) { - if (i915_request_completed(last)) { - tasklet_hi_schedule(&execlists->tasklet); - return; - } - ENGINE_TRACE(engine, "expired last=%llx:%lld, prio=%d, hint=%d, yield?=%s\n", last->fence.context, @@ -2214,6 +2206,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) * we hopefully coalesce several updates into a single * submission. */ +check_secondary: if (!list_is_last(&last->sched.link, &engine->active.requests)) { /*