From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 14180CCF9F8 for ; Thu, 6 Nov 2025 16:29:54 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 4EE1110E94F; Thu, 6 Nov 2025 16:29:53 +0000 (UTC) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by gabe.freedesktop.org (Postfix) with ESMTP id 0F05710E94C for ; Thu, 6 Nov 2025 16:29:52 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E14E11516; Thu, 6 Nov 2025 08:29:43 -0800 (PST) Received: from [10.57.72.2] (unknown [10.57.72.2]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1A74A3F66E; Thu, 6 Nov 2025 08:29:49 -0800 (PST) Message-ID: <50a6bd19-d8a7-4db5-b7c2-c4f0f52b6372@arm.com> Date: Thu, 6 Nov 2025 16:29:48 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 6/8] drm/panthor: Fix the logic that decides when to stop ticking To: Boris Brezillon , Liviu Dudau , =?UTF-8?Q?Adri=C3=A1n_Larumbe?= Cc: dri-devel@lists.freedesktop.org, Florent Tomasin , Heinrich Fink , kernel@collabora.com References: <20251106144656.1012274-1-boris.brezillon@collabora.com> <20251106144656.1012274-7-boris.brezillon@collabora.com> From: Steven Price Content-Language: en-GB In-Reply-To: <20251106144656.1012274-7-boris.brezillon@collabora.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 06/11/2025 14:46, Boris Brezillon wrote: > When we have multiple active groups with the same priority, we need to > keep ticking for the priority rotation to take place. If we don't do > that, we might starve slots with lower priorities. > > It's annoying to deal with that in tick_ctx_update_resched_target(), > so let's add a ::stop_tick field to the tick context which is > initialized to true, and downgraded to false as soon as we detect > something that requires to tick to happen. This way we can complement > the current logic with extra conditions if needed. > > Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block") > Signed-off-by: Boris Brezillon Reviewed-by: Steven Price > --- > drivers/gpu/drm/panthor/panthor_sched.c | 36 ++++++++++++------------- > 1 file changed, 17 insertions(+), 19 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 1eba56e7360d..7b164228af7b 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -1882,6 +1882,7 @@ struct panthor_sched_tick_ctx { > struct panthor_vm *vms[MAX_CS_PER_CSG]; > u32 as_count; > bool immediate_tick; > + bool stop_tick; > u32 csg_upd_failed_mask; > }; > > @@ -1941,10 +1942,17 @@ tick_ctx_pick_groups_from_list(const struct panthor_scheduler *sched, > if (!owned_by_tick_ctx) > group_get(group); > > - list_move_tail(&group->run_node, &ctx->groups[group->priority]); > ctx->group_count++; > + > + /* If we have more than one active group with the same priority, > + * we need to keep ticking to rotate the CSG priority. > + */ > if (group_is_idle(group)) > ctx->idle_group_count++; > + else if (!list_empty(&ctx->groups[group->priority])) > + ctx->stop_tick = false; > + > + list_move_tail(&group->run_node, &ctx->groups[group->priority]); > > if (i == ctx->as_count) > ctx->vms[ctx->as_count++] = group->vm; > @@ -1996,6 +2004,7 @@ tick_ctx_init(struct panthor_scheduler *sched, > memset(ctx, 0, sizeof(*ctx)); > csgs_upd_ctx_init(&upd_ctx); > > + ctx->stop_tick = true; > ctx->min_priority = PANTHOR_CSG_PRIORITY_COUNT; > for (i = 0; i < ARRAY_SIZE(ctx->groups); i++) { > INIT_LIST_HEAD(&ctx->groups[i]); > @@ -2308,32 +2317,21 @@ static u64 > tick_ctx_update_resched_target(struct panthor_scheduler *sched, > const struct panthor_sched_tick_ctx *ctx) > { > - /* We had space left, no need to reschedule until some external event happens. */ > - if (!tick_ctx_is_full(sched, ctx)) > - goto no_tick; > + u64 resched_target; > > - /* If idle groups were scheduled, no need to wake up until some external > - * event happens (group unblocked, new job submitted, ...). > - */ > - if (ctx->idle_group_count) > + if (ctx->stop_tick) > goto no_tick; > > if (drm_WARN_ON(&sched->ptdev->base, ctx->min_priority >= PANTHOR_CSG_PRIORITY_COUNT)) > goto no_tick; > > - /* If there are groups of the same priority waiting, we need to > - * keep the scheduler ticking, otherwise, we'll just wait for > - * new groups with higher priority to be queued. > - */ > - if (!list_empty(&sched->groups.runnable[ctx->min_priority])) { > - u64 resched_target = sched->last_tick + sched->tick_period; > + resched_target = sched->last_tick + sched->tick_period; > > - if (time_before64(sched->resched_target, sched->last_tick) || > - time_before64(resched_target, sched->resched_target)) > - sched->resched_target = resched_target; > + if (time_before64(sched->resched_target, sched->last_tick) || > + time_before64(resched_target, sched->resched_target)) > + sched->resched_target = resched_target; > > - return sched->resched_target - sched->last_tick; > - } > + return sched->resched_target - sched->last_tick; > > no_tick: > sched->resched_target = U64_MAX;