linux-kernel - Re: [RFC] [PATCH] hugetlbfs :shmget with SHM

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Date:	Wed, 30 Jan 2008 15:02:14 +0530
From:	Ciju Rajan K <ciju@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
CC:	William Lee Irwin III <wli@...omorphy.com>,
	aglitke <agl@...ibm.com>
Subject: Re: [RFC] [PATCH] hugetlbfs :shmget with SHM_HUGETLB only works as
 root

Ciju Rajan K wrote:
> William Lee Irwin III wrote:
>> On Fri, Nov 30, 2007 at 12:02:32AM +0530, Ciju Rajan K wrote:
>>>   I tested your patch. But that is not solving the problem.
>>>   If the code change to user_shm_lock() is not a good solution, could 
>>> you please suggest a method so that the normal user is able to 
>>> allocate the huge pages, if his gid is added to 
>>> /proc/sys/vm/hugetlb_shm_group
>>
>> The patch I posted resolves a race unrelated to your issue. Raising your
>> locked memory limits should not be difficult. /etc/limits.conf or similar
>> should set it up for you. You can also change the default rlimit in the
>> kernel and compile it with default limits elevated to what you want your
>> unprivileged process to have to start with if you're truly having lots
>> of trouble getting userspace to set the default limits properly. I'd
>> look in include/asm-generic/resource.h
>>
>>
>> -- wli
> 
> Hi Wli,
> 
> The documentation available in the kernel for huge pages does not talk
> about the issue associated with locked memory limit. I think it would be
> helpful to the users if we mention about this in the documentation. I
> am attaching a small documentation patch.
> 
> Thanks
> Ciju
> 
> Signed-off-by: Ciju Rajan (ciju@...ux.vnet.ibm.com)
> ---
> --- Documentation/vm/hugetlbpage.txt.orig       2008-01-24 
> 16:42:40.000000000 +0530
> +++ Documentation/vm/hugetlbpage.txt    2008-01-29 19:36:45.000000000 +0530
> @@ -108,6 +108,18 @@ a supplementary group and system admin n
>  applications to use any combination of mmaps and shm* calls, though the
>  mount of filesystem will be required for using mmap calls.
> 
> +Note: The default locked limit in the kernel is just 32KB. If the normal
> +user whose gid is present in the file /proc/sys/vm/hugetlb_shm_group needs
> +more memory than this, the default limit must be increased. If pam is 
> installed
> +on your system, resource limits can be configured by installing lines 
> similar
> +to the following in /etc/security/limits.conf:
> +
> +@...egroup      soft    memlock         2097152
> +@...egroup      hard    memlock         2097152
> +
> +Otherwise, you may manipulate the locked limit command directly with 
> 'ulimit'.
> +See its man page for more information.
> +
>  *******************************************************************
> 
>  /*
> 
> -- 
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> 
Wli,
  Can this patch be included in the hugepage documentation?

Thanks
Ciju
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