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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B76D5C4332F for ; Wed, 15 Dec 2021 13:04:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237377AbhLONEY (ORCPT ); Wed, 15 Dec 2021 08:04:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230307AbhLONEX (ORCPT ); Wed, 15 Dec 2021 08:04:23 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 211E4C061574; Wed, 15 Dec 2021 05:04:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=gIifIyPg8CLByWd1i0OMSF1sa+Vo0B9xYqpV36mSTFM=; b=h0EhRqQeNDTk7ndsoAUJvE2YPS Xxc6KIOndvro3Qwhv3FDBt8cXpCSWlqbwD6/cFoFOa7Sz+z6JR25dvpwdjxCkqgYaFYcrvoR0Jx75 SVZtfD6MdNFhJt5Ze68+H5d/3jIV9ZzhuCYyLzlowA6DMsXdwTnTSYRXknujnVNx4LjlD/GaU6yWz AEs7yx4WRJydptDq5JiRyVTXPiAYp7jzVMWoVlHGdrxk77ojBQSQxa9cuHWXmaYOY2eABP4R/iQuj 465JXjK9hKvnzbj4XU755ZMWUqEHQulcQhpvX7dAhUOZ1qL/uhodUCr5zQrXw7WcI52XBsGCz+AhL DjSsoJjw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxTwZ-001VUZ-Oq; Wed, 15 Dec 2021 13:03:40 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id F33F4300348; Wed, 15 Dec 2021 14:03:37 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AA61F2B324D1C; Wed, 15 Dec 2021 14:03:37 +0100 (CET) Date: Wed, 15 Dec 2021 14:03:37 +0100 From: Peter Zijlstra To: Peter Oskolkov Cc: Ingo Molnar , Thomas Gleixner , juri.lelli@redhat.com, Vincent Guittot , dietmar.eggemann@arm.com, Steven Rostedt , Ben Segall , mgorman@suse.de, bristot@redhat.com, Linux Kernel Mailing List , Linux Memory Management List , linux-api@vger.kernel.org, x86@kernel.org, Paul Turner , Peter Oskolkov , Andrei Vagin , Jann Horn , Thierry Delisle Subject: Re: [RFC][PATCH 0/3] sched: User Managed Concurrency Groups Message-ID: References: <20211214204445.665580974@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 15, 2021 at 11:06:20AM +0100, Peter Zijlstra wrote: > On Tue, Dec 14, 2021 at 07:46:25PM -0800, Peter Oskolkov wrote: > > On Tue, Dec 14, 2021 at 12:55 PM Peter Zijlstra wrote: > > > > > > Hi, > > > > > > This is actually tested code; but still missing the SMP wake-to-idle machinery. > > > I still need to think about that. > > > > Thanks, Peter! > > > > At a first glance, your main patch does not look much smaller than > > mine, and I thought the whole point of re-doing it was to throw away > > extra features and make things smaller/simpler... > > Well, simpler was the goal. I didn't really focus on size much. It isn't > really big to begin with. > > But yes, it has 5 hooks now, 3 syscalls and lots of comments and all > that under 900 lines, not bad I'd say. > > Also I think you wanted something like this? I'm not sure of the LAZY > name, but I can't seem to come up with anything saner atm. > > > --- > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1297,6 +1297,7 @@ struct task_struct { > > #ifdef CONFIG_UMCG > /* setup by sys_umcg_ctrl() */ > + u32 umcg_flags; > clockid_t umcg_clock; > struct umcg_task __user *umcg_task; > > --- a/include/uapi/linux/umcg.h > +++ b/include/uapi/linux/umcg.h > @@ -133,11 +133,13 @@ struct umcg_task { > * @UMCG_CTL_REGISTER: register the current task as a UMCG task > * @UMCG_CTL_UNREGISTER: unregister the current task as a UMCG task > * @UMCG_CTL_WORKER: register the current task as a UMCG worker > + * @UMCG_CTL_LAZY: don't wake server on runnable enqueue > */ > enum umcg_ctl_flag { > UMCG_CTL_REGISTER = 0x00001, > UMCG_CTL_UNREGISTER = 0x00002, > UMCG_CTL_WORKER = 0x10000, > + UMCG_CTL_LAZY = 0x20000, > }; > > #endif /* _UAPI_LINUX_UMCG_H */ > --- a/kernel/sched/umcg.c > +++ b/kernel/sched/umcg.c > @@ -416,6 +416,27 @@ static int umcg_enqueue_runnable(struct > } > > /* > + * Enqueue tsk to it's server's runnable list and wake the server for pickup if > + * so desired. Notable LAZY workers will not wake the server and rely on the > + * server to do pickup whenever it naturally runs next. > + * > + * Returns: > + * 0: success > + * -EFAULT > + */ > +static int umcg_enqueue_and_wake(struct task_struct *tsk, bool force) > +{ > + int ret = umcg_enqueue_runnable(tsk); > + if (ret) > + return ret; > + > + if (force || !(tsk->umcg_flags & UMCG_CTL_LAZY)) > + ret = umcg_wake_server(tsk); > + > + return ret; > +} Aah, this has a problem when the server is otherwise idle. I think we need that TF_IDLE thing for this too. Let me go write a test-case for all this.