From patchwork Mon Jan 28 01:02:21 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 10783143 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 5D06C91E for ; Mon, 28 Jan 2019 01:04:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4D2C028681 for ; Mon, 28 Jan 2019 01:04:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 41B33292A9; Mon, 28 Jan 2019 01:04:58 +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 D03CA28681 for ; Mon, 28 Jan 2019 01:04:57 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 93C5C6E30B; Mon, 28 Jan 2019 01:04:55 +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 8D0506E099 for ; Mon, 28 Jan 2019 01:04:45 +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 15370500-1500050 for multiple; Mon, 28 Jan 2019 01:02:47 +0000 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Mon, 28 Jan 2019 01:02:21 +0000 Message-Id: <20190128010245.20148-4-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190128010245.20148-1-chris@chris-wilson.co.uk> References: <20190128010245.20148-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 04/28] drm/i915/execlists: Suppress redundant 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 On unwinding the active request we give it a small (limited to internal priority levels) boost to prevent it from being gazumped a second time. However, this means that it can be promoted to above the request that triggered the preemption request, causing a preempt-to-idle cycle for no change. We can avoid this if we take the boost into account when checking if the preemption request is valid. v2: After preemption the active request will be after the preemptee if they end up with equal priority. Signed-off-by: Chris Wilson --- drivers/gpu/drm/i915/intel_lrc.c | 39 ++++++++++++++++++++++++++++---- 1 file changed, 35 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 79adf9827f02..12db24b30e78 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -164,6 +164,8 @@ #define WA_TAIL_DWORDS 2 #define WA_TAIL_BYTES (sizeof(u32) * WA_TAIL_DWORDS) +#define ACTIVE_PRIORITY (I915_PRIORITY_NEWCLIENT) + static int execlists_context_deferred_alloc(struct i915_gem_context *ctx, struct intel_engine_cs *engine, struct intel_context *ce); @@ -182,6 +184,34 @@ static inline int rq_prio(const struct i915_request *rq) return rq->sched.attr.priority; } +static inline int active_prio(const struct i915_request *rq) +{ + int prio = rq_prio(rq); + + /* + * On unwinding the active request, we give it a priority bump + * equivalent to a freshly submitted request. This protects it from + * being gazumped again, but it would be preferable if we didn't + * let it be gazumped in the first place! + * + * See __unwind_incomplete_requests() + */ + if ((prio & ACTIVE_PRIORITY) != ACTIVE_PRIORITY && + i915_request_started(rq)) { + /* + * After preemption, we insert the active request at the + * end of the new priority level. This means that we will be + * _lower_ priority than the preemptee all things equal (and + * so the preemption is valid), so adjust our comparison + * accordingly. + */ + prio |= ACTIVE_PRIORITY; + prio--; + } + + return prio; +} + static int queue_prio(const struct intel_engine_execlists *execlists) { struct i915_priolist *p; @@ -202,7 +232,7 @@ static int queue_prio(const struct intel_engine_execlists *execlists) static inline bool need_preempt(const struct intel_engine_cs *engine, const struct i915_request *rq) { - const int last_prio = rq_prio(rq); + int last_prio; if (!intel_engine_has_preemption(engine)) return false; @@ -222,6 +252,7 @@ static inline bool need_preempt(const struct intel_engine_cs *engine, * preempt. If that hint is stale or we may be trying to preempt * ourselves, ignore the request. */ + last_prio = active_prio(rq); if (!__execlists_need_preempt(engine->execlists.preempt_priority_hint, last_prio)) return false; @@ -347,7 +378,7 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine) { struct i915_request *rq, *rn, *active = NULL; struct list_head *uninitialized_var(pl); - int prio = I915_PRIORITY_INVALID | I915_PRIORITY_NEWCLIENT; + int prio = I915_PRIORITY_INVALID | ACTIVE_PRIORITY; lockdep_assert_held(&engine->timeline.lock); @@ -379,8 +410,8 @@ __unwind_incomplete_requests(struct intel_engine_cs *engine) * stream, so give it the equivalent small priority bump to prevent * it being gazumped a second time by another peer. */ - if (!(prio & I915_PRIORITY_NEWCLIENT)) { - prio |= I915_PRIORITY_NEWCLIENT; + if ((prio & ACTIVE_PRIORITY) != ACTIVE_PRIORITY) { + prio |= ACTIVE_PRIORITY; active->sched.attr.priority = prio; list_move_tail(&active->sched.link, i915_sched_lookup_priolist(engine, prio));