From: Steven Sistare <steven.sistare@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: subhra mazumdar <subhra.mazumdar@oracle.com>,
linux-kernel@vger.kernel.org, mingo@redhat.com,
dhaval.giani@oracle.com
Subject: Re: [RESEND RFC PATCH V3] sched: Improve scalability of select_idle_sibling using SMT balance
Date: Fri, 2 Feb 2018 12:39:20 -0500 [thread overview]
Message-ID: <ed78c502-c1f8-43b3-f3d4-e0256e4085ee@oracle.com> (raw)
In-Reply-To: <20180202172153.GO2269@hirez.programming.kicks-ass.net>
On 2/2/2018 12:21 PM, Peter Zijlstra wrote:
> On Fri, Feb 02, 2018 at 11:53:40AM -0500, Steven Sistare wrote:
>> It might be interesting to add a tunable for the number of random choices to
>> make, and clamp it at the max nr computed from avg_cost in select_idle_cpu.
>
> This needs a fairly complicated PRNG for it would need to visit each
> possible CPU once before looping. A LFSR does that, but requires 2^n-1
> elements and we have topology masks that don't match that.. The trivial
> example is something with 6 cores.
Or keep it simple and accept the possibility of choosing the same candidate
more than once.
>> Or, choose a random starting point and then search for nr sequential
>> candidates; possibly limited by a tunable.
>
> And this is basically what we already do. Except with the task-cpu
> instead of a per-cpu rotor.
Righto. Disregard this suggestion.
- Steve
next prev parent reply other threads:[~2018-02-02 17:44 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-29 23:31 subhra mazumdar
2018-02-01 12:33 ` Peter Zijlstra
2018-02-01 13:33 ` Peter Zijlstra
2018-02-02 16:53 ` Steven Sistare
2018-02-02 17:17 ` Peter Zijlstra
2018-02-02 17:36 ` Steven Sistare
2018-02-02 19:58 ` Peter Zijlstra
2018-02-02 20:51 ` Steven Sistare
2018-02-02 17:37 ` Subhra Mazumdar
2018-02-05 12:19 ` Peter Zijlstra
2018-02-05 22:09 ` Subhra Mazumdar
2018-02-06 9:12 ` Peter Zijlstra
2018-02-07 0:30 ` Subhra Mazumdar
2018-02-07 8:42 ` Peter Zijlstra
2018-02-07 23:10 ` Subhra Mazumdar
2018-02-02 17:21 ` Peter Zijlstra
2018-02-02 17:39 ` Steven Sistare [this message]
2018-02-02 18:34 ` Steven Sistare
2018-02-02 20:04 ` Peter Zijlstra
2018-02-02 21:17 ` Steven Sistare
2018-02-03 3:47 ` Mike Galbraith
2018-02-02 19:59 ` Peter Zijlstra
2018-02-02 21:06 ` Steven Sistare
2018-02-05 12:48 ` Peter Zijlstra
2018-02-05 13:54 ` Mike Galbraith
2018-02-05 17:03 ` Peter Zijlstra
2018-02-05 22:32 ` Subhra Mazumdar
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