linux-kernel - Re: [PATCH] mm/mempolicy: failed to disable numa balancing

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Message-Id: <20221202115954.a226f8ef3051266d04caff54@linux-foundation.org>
Date:   Fri, 2 Dec 2022 11:59:54 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     tzm <tcm1030@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: Re: [PATCH] mm/mempolicy: failed to disable numa balancing

On Fri,  2 Dec 2022 22:16:30 +0800 tzm <tcm1030@....com> wrote:

> It will be failed to  disable numa balancing policy permanently by passing
> <numa_balancing=disable> to boot cmdline parameters.
> The numabalancing_override variable is int and 1 for enable -1 for disable.
> So, !enumabalancing_override will always be true, which cause this bug.

That's really old code!

> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2865,7 +2865,7 @@ static void __init check_numabalancing_enable(void)
>  	if (numabalancing_override)
>  		set_numabalancing_state(numabalancing_override == 1);
>  
> -	if (num_online_nodes() > 1 && !numabalancing_override) {
> +	if (num_online_nodes() > 1 && (numabalancing_override == 1)) {
>  		pr_info("%s automatic NUMA balancing. Configure with numa_balancing= or the kernel.numa_balancing sysctl\n",
>  			numabalancing_default ? "Enabling" : "Disabling");
>  		set_numabalancing_state(numabalancing_default);

Looks right to me.  Mel?

After eight years, I wonder if we actually need this.