linux-kernel - Re: [PATCH 3/4] sched/numa: Apply imbalance limitations consistently

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Message-ID: <YoT7xtVc0f3DVCKL@hirez.programming.kicks-ass.net>
Date:   Wed, 18 May 2022 15:59:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] sched/numa: Apply imbalance limitations consistently

On Wed, May 18, 2022 at 11:46:52AM +0100, Mel Gorman wrote:

> > (Although I do wonder about that 25% figure in the comment; that doesn't
> > seem to relate to any actual code anymore)
> > 
> 
> You're right, by the end of the series it's completely inaccurate and
> currently it's not accurate if there are multiple LLCs per node. I
> adjusted the wording to "Allow a NUMA imbalance if busy CPUs is less
> than the maximum threshold. Above this threshold, individual tasks may
> be contending for both memory bandwidth and any shared HT resources."
> 

Looks good. Meanwhile I saw a 0-day complaint that this regresses
something something unixbench by a bit. Do we care enough? I suppose
this is one of those trade-off patches again, win some, loose some.