linux-kernel - Re: [PATCH RFC 1/5] sched,numa: build table of node hop distance

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Message-ID: <543A81E4.4090504@redhat.com>
Date:	Sun, 12 Oct 2014 09:28:04 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, mgorman@...e.de, chegu_vinod@...com,
	mingo@...nel.org, efault@....de, vincent.guittot@...aro.org
Subject: Re: [PATCH RFC 1/5] sched,numa: build table of node hop distance

On 10/12/2014 09:17 AM, Peter Zijlstra wrote:
> On Wed, Oct 08, 2014 at 03:37:26PM -0400, riel@...hat.com wrote:
>> +	sched_domains_numa_hops = kzalloc(sizeof(int) * nr_node_ids * nr_node_ids, GFP_KERNEL);
>> +	if (!sched_domains_numa_hops)
>> +		return;
>
> That's potentially a _BIG_ table (1M for a 512 node system).
> The node_distance has magic allocations and is of u8 size, is there any
> way we can re-use node_distance and avoid a second O(n^2) allocation?

You are right, this should be a u8 at the least.

Beyond that, I am not convinced that merging things into
the same array is worthwhile, since (IIRC) nr_node_ids
should be set to the actual number of nodes on the system
by then.
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