From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753003AbbC3QqA (ORCPT ); Mon, 30 Mar 2015 12:46:00 -0400 Received: from mail-db3on0061.outbound.protection.outlook.com ([157.55.234.61]:21056 "EHLO emea01-db3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752300AbbC3Qp5 (ORCPT ); Mon, 30 Mar 2015 12:45:57 -0400 Message-ID: <55197DB5.7010000@ezchip.com> Date: Mon, 30 Mar 2015 12:45:41 -0400 From: Chris Metcalf User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Rik van Riel , , Frederic Weisbecker , Steven Rostedt , "Paul E. McKenney" , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Borislav Petkov , Li Zhong , Mike Galbraith , Kevin Hilman Subject: Re: [PATCH 3/4] nohz: add tick_nohz_full_clear_cpus() API References: <1427224895-30830-1-git-send-email-cmetcalf@ezchip.com> <1427224895-30830-4-git-send-email-cmetcalf@ezchip.com> <551977C1.4000303@ezchip.com> <55197CA2.9040706@redhat.com> In-Reply-To: <55197CA2.9040706@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [12.216.194.146] X-ClientProxiedBy: BY1PR0201CA0019.namprd02.prod.outlook.com (25.160.191.157) To DB3PR02MB0539.eurprd02.prod.outlook.com (25.160.51.150) Authentication-Results: linaro.org; dkim=none (message not signed) header.d=none; X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:DB3PR02MB0539; X-Microsoft-Antispam-PRVS: X-Forefront-Antispam-Report: BMV:1;SFV:NSPM;SFS:(10009020)(6049001)(6009001)(377454003)(51704005)(479174004)(24454002)(41574002)(46034005)(92566002)(62966003)(107886001)(36756003)(46102003)(77156002)(42186005)(2950100001)(87976001)(50466002)(87266999)(19580405001)(40100003)(76176999)(59896002)(122386002)(65816999)(15975445007)(93886004)(23676002)(83506001)(77096005)(33656002)(50986999)(54356999)(65956001)(64126003)(19580395003)(86362001)(99136001)(80316001)(66066001)(7059030)(921003)(1121003)(18886065003);DIR:OUT;SFP:1101;SCL:1;SRVR:DB3PR02MB0539;H:[10.7.0.41];FPR:;SPF:None;MLV:sfv;LANG:en; X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(601004)(5005006)(5002010);SRVR:DB3PR02MB0539;BCL:0;PCL:0;RULEID:;SRVR:DB3PR02MB0539; X-Forefront-PRVS: 05315CBE52 X-OriginatorOrg: ezchip.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Mar 2015 16:45:52.3562 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB3PR02MB0539 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/30/2015 12:41 PM, Rik van Riel wrote: > On 03/30/2015 12:20 PM, Chris Metcalf wrote: >> I wanted to ping the patch below again, since I haven't heard any >> feedback. >> >> I note that Rik van Riel's change posted this weekend offers similar >> functionality for userspace. My change offers a convenient API >> for, e.g., kernel drivers setting up default irq balancing. >> >> https://lkml.org/lkml/2015/3/28/94 > I submitted a patch to irqbalance to exclude nohz_full > cpus from having irqs assigned to them. I could see > the same thing being useful for in-kernel irq assignment, > especially for multi-queue devices that set up irqs on > multiple CPUs. > >> An alternate API would be one that just returned the full no_hz >> cpumask to kernel callers; I'd be happy with that as well, but my >> instinct was to make the API as narrow as possible to start with. >> >> Comments? > What drivers and subsystems are you targeting? At the moment, just the on-chip tilegx ethernet controller (drivers/net/ethernet/tile/tilegx.c) but I'm pushing to upstream a number of other commits from the Tilera "dataplane" mode, some of which include code that acts on cpumasks as well. > I am just looking at blk-mq now, and it seems like the > API most appropriate for that would be an inline function > that tests whether or not a CPU is nohz_full. That API already exists - tick_nohz_full_cpu(). > for_each_possible_cpu(i) { > > ... > > if (cpu_nohz_full(i)) > continue; > > } > > A lot of the other code in drivers and subsystems that > set up per-cpu queues and irqs seem to iterate over all > CPUs at init time, and could benefit from a function > allowing them to skip nohz_full CPUs. > > Your tick_nohz_full_clear_cpus() function seems reasonable > too, for code that uses a cpumask to set up per cpu stuff. I'm happy to ask for a pull request for the tile architecture that includes that commit, if no one objects. I'd be happier if someone acked the patch more explicitly, though. Thanks! > From: Chris Metcalf > > This is useful, for example, to modify a cpumask to avoid the > nohz cores so that interrupts aren't sent to them. > > Signed-off-by: Chris Metcalf > --- > Motivated by patch 4/4 in this series. > > include/linux/tick.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/include/linux/tick.h b/include/linux/tick.h > index 9c085dc12ae9..d53ad4892a39 100644 > --- a/include/linux/tick.h > +++ b/include/linux/tick.h > @@ -186,6 +186,12 @@ static inline bool tick_nohz_full_cpu(int cpu) > return cpumask_test_cpu(cpu, tick_nohz_full_mask); > } > +static inline void tick_nohz_full_clear_cpus(struct cpumask *mask) > +{ > + if (tick_nohz_full_enabled()) > + cpumask_andnot(mask, mask, tick_nohz_full_mask); > +} > + > extern void __tick_nohz_full_check(void); > extern void tick_nohz_full_kick(void); > extern void tick_nohz_full_kick_cpu(int cpu); > @@ -194,6 +200,7 @@ extern void __tick_nohz_task_switch(struct > task_struct *tsk); > #else > static inline bool tick_nohz_full_enabled(void) { return false; } > static inline bool tick_nohz_full_cpu(int cpu) { return false; } > +static inline void tick_nohz_full_clear_cpus(struct cpumask *mask) { } > static inline void __tick_nohz_full_check(void) { } > static inline void tick_nohz_full_kick_cpu(int cpu) { } > static inline void tick_nohz_full_kick(void) { } -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com