From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7F99355030 for ; Wed, 17 Dec 2025 15:49:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765986556; cv=none; b=dCYv0Pbpr/+NHSIASYKMOKjVf3qZS1wpjwf4ZV8D2c4yy6wHm+uCNREg4HHCnSCiPZ39umw4K2tiPSXKwWhm+E1wWRP5ZPFWoRlU8l2uabunUdedawZb5J1K27cQXIrbF1b4b5GLz5HIDsizferEyFGChsWPHhG135YvD8WEC8A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765986556; c=relaxed/simple; bh=ej7TTVTeGnBUqaRwlQnvTPhYft8GTVTgUYErJC5s1Bk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=B+fV4+rbozDdwvnpjS6a2YHtGYxicloLKhrQTFOHpNSPLmKjVWwDd01TGoIB1O1GVS7EssFi4NqHAedv3T+DvIgj1SqtdKaUvudHMtDwebXtEcWEwjsBkSUo2/m1iarbINW0WaK38d9roXd/ImKXthKn+tkDyVPwg+465medRzY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ca2NqY2Z; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=spwPvRAV; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ca2NqY2Z"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="spwPvRAV" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1765986553; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=9bJTbj2QHR/bxiaOEFbouYE+C6nf3xnn/6jMSMVKkAk=; b=ca2NqY2Z+LsZs1Ai3rL7BxhuR0P9r0LDGgzf1c3lMXkjAipVXBAT0tgEFSBvOJqaI9639N ug+UWYM8582plrwrTWTejdI/rxBcIdDwgy+LeD1e3g43HCBPzvvDxnPdnW9UgWnAN8nswh uiA7vbyLDBnF5M7Yg52yn1M1rgmYeoI= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-201-ls-5XNMiP-GsRl-bSXBJ6w-1; Wed, 17 Dec 2025 10:49:12 -0500 X-MC-Unique: ls-5XNMiP-GsRl-bSXBJ6w-1 X-Mimecast-MFC-AGG-ID: ls-5XNMiP-GsRl-bSXBJ6w_1765986551 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4788112ec09so43475965e9.3 for ; Wed, 17 Dec 2025 07:49:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1765986551; x=1766591351; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=9bJTbj2QHR/bxiaOEFbouYE+C6nf3xnn/6jMSMVKkAk=; b=spwPvRAVjPd8bAiYboWPfTfdFQRAGJ15XAMwYEoFXDhSZefh54e7XdccsV5Llc7Uwn 2Cd4aUsk59IcNoYtlvXaU1Mi6aoRLHZ6uAPodYzH5JRhyfmUM8GEM4l0xNB9+tAy0zub 9SZNiNhKId5RxSxLB6gIRe5xfrR4+KiqLBLzKPse1zd9s95n51KT6b8aIR/UGNVPf9Kn qmT2ZrxAaWp6fQhFzYdNQuC8YE+2Tqtl8upLZ+fN/gbKh/DUqQXaAP9Kqtpts0PYOwHq uEJvmQTonCLkfKmsTyfZODQI1KNnPHzW0oRFGVH2haIcbyNlOlIV8Fu6orjabELdfyFz FX+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1765986551; x=1766591351; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=9bJTbj2QHR/bxiaOEFbouYE+C6nf3xnn/6jMSMVKkAk=; b=e4OKWlyNDjUPOyUjwoCbO3yDcA3Pr3F051cEagMq0dadi1Guq4TDjGNSfzJ6YqClyH 3hmHbmZZh18zpLcVUyrSBPmgo8oXKmOkvyNqlABS9dAMYWch76jkOLO71X2y2Sc9R6qA nrxNuH8SyKdgdCrvoVgC9brclmQC1pK3LS9j9B9RBaxKtt0thFrf+lxpIxy6rhIvucrB irlvtwGjh5iHpsmskBJ8vRIGusFSgyD8yRodsH70Z+h5WiPPRljnrufR5nt4FJGVSpc7 FqJT0K1zVsDVwjdiCACLd4r7Clr1eaUXPsvFbQPMwQwnGQij03Sdra/3G9u4PKwb7Ecg wU4w== X-Forwarded-Encrypted: i=1; AJvYcCU8IWlDwK628ap6kn1CRnCV+0vFpVk6w/INSZZauTdk3EkW91EU7WwS/LZ9lh7DnKq+472DjCIGQOuVnvDDbOI=@vger.kernel.org X-Gm-Message-State: AOJu0Yy09JT4jNQl9hrKen/lUCDJQ4KrCQO+tOPznOTSs0b3MosycJOu f3dGrXr6s+/Rn9A+UJBS/UUCl0lSyhQesoq36AioxQgel+woGvDMoty62YLJjuohGzb5ln29Faz lMGiAeT/pBCwahD4qf8W0pg/Gvzu+rDjLFn/BYnsl+OwOyzf8Lf3BciCulncxcA1F5W8zpw== X-Gm-Gg: AY/fxX5wElPsyYjeVEFjmYjIQD9ZeJgB77f8XJ2s5DAmc0uSnBJvG48Cc8kUF4CNf33 GOIB/UA/PEPdBhGq4ad3TCpXNeJsFiAXNxBX53e4K7gWy0WUvEm4jMQIMP8xV0Vx8GtleoJmCJb w/sU/WACK5idAIHECOjmMfqINIBWBg/1zl0KS83g+oUlTltoKwG6kiPoXpiBQbzOmYiO1YsSz5U R4C+bLMJtQ4S/sQZdlALhYzP0Zahkae9Pv1inLmNHBhTbfWkYqCCu++Aon4BNpeHAIJ52n6EoHO XLvVkF/HkWzXjVbsZfgCj3A/t7zsk0L0yNsBLinQ+hT5ljGjFoyZHzSNP1JAOFXaqtmJ0zM5V4J Ftk1AEO4XQouGhcej4aqVF4l4ZGWskV9OM2iUxGmh X-Received: by 2002:a05:600c:1c88:b0:477:8a29:582c with SMTP id 5b1f17b1804b1-47a8f917533mr206283905e9.34.1765986550779; Wed, 17 Dec 2025 07:49:10 -0800 (PST) X-Google-Smtp-Source: AGHT+IGJ+ughGVWwzvXsaWm1dblcs5eRzcKirhAt+kak2tJQKEnBlZisL9+a1O+Ahuhxi1HwalxGKQ== X-Received: by 2002:a05:600c:1c88:b0:477:8a29:582c with SMTP id 5b1f17b1804b1-47a8f917533mr206283615e9.34.1765986550400; Wed, 17 Dec 2025 07:49:10 -0800 (PST) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.129.40]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47bd911a9bcsm32202995e9.6.2025.12.17.07.49.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 07:49:09 -0800 (PST) Date: Wed, 17 Dec 2025 16:49:02 +0100 From: Juri Lelli To: Andrea Righi Cc: Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Tejun Heo , David Vernet , Changwoo Min , Shuah Khan , Joel Fernandes , Christian Loehle , Emil Tsalapatis , sched-ext@lists.linux.dev, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/7] sched_ext: Add a DL server for sched_ext tasks Message-ID: References: <20251217093923.1556187-1-arighi@nvidia.com> <20251217093923.1556187-5-arighi@nvidia.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251217093923.1556187-5-arighi@nvidia.com> Hi! On 17/12/25 10:35, Andrea Righi wrote: > sched_ext currently suffers starvation due to RT. The same workload when > converted to EXT can get zero runtime if RT is 100% running, causing EXT > processes to stall. Fix it by adding a DL server for EXT. ... > v4: - initialize EXT server bandwidth reservation at init time and > always keep it active (Andrea Righi) > - check for rq->nr_running == 1 to determine when to account idle > time (Juri Lelli) > v3: - clarify that fair is not the only dl_server (Juri Lelli) > - remove explicit stop to reduce timer reprogramming overhead > (Juri Lelli) > - do not restart pick_task() when it's invoked by the dl_server > (Tejun Heo) > - depend on CONFIG_SCHED_CLASS_EXT (Andrea Righi) > v2: - drop ->balance() now that pick_task() has an rf argument > (Andrea Righi) > > Tested-by: Christian Loehle > Co-developed-by: Joel Fernandes > Signed-off-by: Joel Fernandes > Signed-off-by: Andrea Righi > --- ... > @@ -3090,6 +3123,15 @@ static void switching_to_scx(struct rq *rq, struct task_struct *p) > static void switched_from_scx(struct rq *rq, struct task_struct *p) > { > scx_disable_task(p); > + > + /* > + * After class switch, if the DL server is still active, restart it so > + * that DL timers will be queued, in case SCX switched to higher class. > + */ > + if (dl_server_active(&rq->ext_server)) { > + dl_server_stop(&rq->ext_server); > + dl_server_start(&rq->ext_server); > + } > } We might have discussed this already, in that case I forgot, sorry. But, why we do need to start the server again if switched from scx? Couldn't make sense of the comment that is already present. Thanks, Juri