linux-kernel - Re: is this a problem of numactl in RedHat7.0 ?

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Message-ID: <55DA9A4B.10203@huawei.com>
Date:	Mon, 24 Aug 2015 12:15:07 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Rik van Riel <riel@...hat.com>
CC:	LKML <linux-kernel@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
	Xiexiuqi <xiexiuqi@...wei.com>
Subject: Re: is this a problem of numactl in RedHat7.0 ?

On 2015/8/22 4:53, Rik van Riel wrote:

> On 08/21/2015 05:27 AM, Xishi Qiu wrote:
>> I use numactl(--localalloc) tool run a test case, but it shows that
>> the numa policy is prefer, I don't know why.
> 
> The kernel implements MPOL_PREFERRED and MPOL_LOCAL
> in the same way. Look at this code in mpol_new(),
> in mm/mempolicy.c:
> 

user:
"numactl --localalloc" wil call
	main()
	  numa_set_localalloc()
	    setpol(MPOL_DEFAULT, numa_no_nodes_ptr);
	      set_mempolicy()
	        syscall(__NR_set_mempolicy,mode,nmask,maxnode);

kernel:
	do_set_mempolicy()
	  mpol_new()
		if (mode == MPOL_DEFAULT) {
			if (nodes && !nodes_empty(*nodes))
				return ERR_PTR(-EINVAL);
			return NULL;  // return from here
		}

>         /*
>          * MPOL_PREFERRED cannot be used with MPOL_F_STATIC_NODES or
>          * MPOL_F_RELATIVE_NODES if the nodemask is empty (local allocation).
>          * All other modes require a valid pointer to a non-empty nodemask.
>          */
>         if (mode == MPOL_PREFERRED) {
>                 if (nodes_empty(*nodes)) {
>                         if (((flags & MPOL_F_STATIC_NODES) ||
>                              (flags & MPOL_F_RELATIVE_NODES)))
>                                 return ERR_PTR(-EINVAL);
>                 }
>         } else if (mode == MPOL_LOCAL) {
>                 if (!nodes_empty(*nodes))
>                         return ERR_PTR(-EINVAL);
>                 mode = MPOL_PREFERRED;
>         } else if (nodes_empty(*nodes))
>                 return ERR_PTR(-EINVAL);
> 
> 
> 
> 



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