linux-kernel - Re: [PATCH 04/10] sched/fair: Dynamically update cfs_overload

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fbb2478e-41f0-37c7-7c22-f8748fa08389@oracle.com>
Date:   Mon, 22 Oct 2018 14:43:44 -0400
From:   Steven Sistare <steven.sistare@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, subhra.mazumdar@...cle.com,
        dhaval.giani@...cle.com, rohit.k.jain@...cle.com,
        daniel.m.jordan@...cle.com, pavel.tatashin@...rosoft.com,
        matt@...eblueprint.co.uk, umgwanakikbuti@...il.com,
        riel@...hat.com, jbacik@...com, juri.lelli@...hat.com,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 04/10] sched/fair: Dynamically update cfs_overload_cpus

On 10/22/2018 12:56 PM, Peter Zijlstra wrote:
> On Mon, Oct 22, 2018 at 07:59:35AM -0700, Steve Sistare wrote:
>> An overloaded CPU has more than 1 runnable task.  When a CFS task wakes
>> on a CPU, if h_nr_running transitions from 1 to more, then set the CPU in
>> the cfs_overload_cpus bitmap.  When a CFS task sleeps, if h_nr_running
>> transitions from 2 to less, then clear the CPU in cfs_overload_cpus.
> 
>> @@ -5111,8 +5147,12 @@ static inline void hrtick_update(struct rq *rq)
>>  		update_cfs_group(se);
>>  	}
>>  
>> -	if (!se)
>> +	if (!se) {
>>  		add_nr_running(rq, 1);
>> +		if (prev_nr == 1)
>> +			overload_set(rq);
>> +
>> +	}
> 
> This is very similar to what RT already has, except they also track if
> the tasks in question is in fact migratable (p->nr_cpus_allowed > 1).
> 
> And similarly, it might make sense to use the sparse mask thing over
> there.

Yes.  I forgot to mention RT as likely follow on work.

- Steve