linux-kernel - Re: [PATCH 16/19] sched/numa: Detect if node actively handling migration

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: <1528142755.7898.122.camel@surriel.com>
Date:   Mon, 04 Jun 2018 16:05:55 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 16/19] sched/numa: Detect if node actively handling
 migration

On Mon, 2018-06-04 at 15:30 +0530, Srikar Dronamraju wrote:

> @@ -1554,6 +1562,9 @@ static void task_numa_compare(struct
> task_numa_env *env,
>  	if (READ_ONCE(dst_rq->numa_migrate_on))
>  		return;
>  
> +	if (*move && READ_ONCE(pgdat->active_node_migrate))
> +		*move = false;

Why not do this check in task_numa_find_cpu?

That way you won't have to pass this in as a
pointer, and you also will not have to recalculate
NODE_DATA(cpu_to_node(env->dst_cpu)) for every CPU.

>  	/*
> +	 * If the numa importance is less than SMALLIMP,

              ^^^ numa improvement

> +	 * task migration might only result in ping pong
> +	 * of tasks and also hurt performance due to cache
> +	 * misses.
> +	 */
> +	if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
> +		goto unlock;

I can see a use for the first test, but why limit the
search for the best score once you are past the
threshold?

I don't understand the use for that second test.

What workload benefits from it?

-- 
All Rights Reversed.
Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)