linux-kernel - Re: [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO

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Message-ID: <20180803171538.GD2494@hirez.programming.kicks-ass.net>
Date:   Fri, 3 Aug 2018 19:15:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Daniel Drake <drake@...lessm.com>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Christopher Lameter <cl@...ux.com>,
        Mike Galbraith <efault@....de>,
        Shakeel Butt <shakeelb@...gle.com>,
        Peter Enderborg <peter.enderborg@...y.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH 8/9] psi: pressure stall information for CPU, memory, and
 IO

On Wed, Aug 01, 2018 at 11:19:57AM -0400, Johannes Weiner wrote:
> +	/* total= */
> +	for (s = 0; s < NR_PSI_STATES - 1; s++)
> +		group->total[s] += div_u64(deltas[s], max(nonidle_total, 1UL));

Just a nit; probably not worth fixing.

This looses the remainder of that division. But since the divisor is
variable it becomes really hard to not loose something at some point.