linux-kernel - Re: [PATCH] x86: numa: setup_node_data(): drop dead code and rename function

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Message-ID: <20140626110501.78bb611d@redhat.com>
Date:	Thu, 26 Jun 2014 11:05:01 -0400
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	isimatu.yasuaki@...fujitsu.com, yinghai@...nel.org,
	andi@...stfloor.org, akpm@...ux-foundation.org, rientjes@...gle.com
Subject: Re: [PATCH] x86: numa: setup_node_data(): drop dead code and rename
 function

On Thu, 26 Jun 2014 10:51:11 -0400
Rik van Riel <riel@...hat.com> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 06/19/2014 10:20 PM, Luiz Capitulino wrote:
> 
> > @@ -523,8 +508,17 @@ static int __init numa_register_memblks(struct
> > numa_meminfo *mi) end = max(mi->blk[i].end, end); }
> > 
> > -		if (start < end) -			setup_node_data(nid, start, end); +		if
> > (start >= end) +			continue; + +		/* +		 * Don't confuse VM with a
> > node that doesn't have the +		 * minimum amount of memory: +		 */ +
> > if (end && (end - start) < NODE_MIN_SIZE) +			continue; + +
> > alloc_node_data(nid); }
> 
> Minor nit.  If we skip a too-small node, should we remember that we
> did so, and add its memory to another node, assuming it is physically
> contiguous memory?

Interesting point. Honest question, please disregard if this doesn't
make sense: but won't this affect automatic numa performance? Because
the kernel won't know that that extra memory actually pertains to another
node and hence that extra memory will have a difference distance of the
node that's making use it of it.

If my thinking is wrong or if even then you believe this is a good feature,
I can work on it on a different patch, as this check is not being introduced
by this patch. Although I also wonder how many numa machines have such small
nodes...

> Other than that...
> 
> Acked-by: Rik van Riel <riel@...hat.com>

Thanks!

> 
> - -- 
> All rights reversed
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