linux-kernel - Re: [PATCH RFC] hugetlbfs 'noautofill' mount option

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Message-ID: <b189b36e-8cd0-cf59-ba6c-8bd7412b11b7@oracle.com>
Date:   Tue, 16 May 2017 09:51:40 -0700
From:   Prakash Sangappa <prakash.sangappa@...cle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH RFC] hugetlbfs 'noautofill' mount option



On 5/9/17 1:59 PM, Prakash Sangappa wrote:
>
>
> On 5/9/17 1:58 AM, Christoph Hellwig wrote:
>> On Mon, May 08, 2017 at 03:12:42PM -0700, prakash.sangappa wrote:
>>> Regarding #3 as a general feature, do we want to
>>> consider this and the complexity associated with the
>>> implementation?
>> We have to.  Given that no one has exclusive access to hugetlbfs
>> a mount option is fundamentally the wrong interface.
>
>
> A hugetlbfs filesystem may need to be mounted for exclusive use by
> an application. Note, recently the 'min_size' mount option was added
> to hugetlbfs, which would reserve minimum number of huge pages
> for that filesystem for use by an application. If the filesystem with
> min size specified, is not setup for exclusive use by an application,
> then the purpose of reserving huge pages is defeated.  The
> min_size option was for use by applications like the database.
>
> Also, I am investigating enabling hugetlbfs mounts within user
> namespace's mount namespace. That would allow an application
> to mount a hugetlbfs filesystem inside a namespace exclusively for
> its use, running as a non root user. For this it seems like the 
> 'min_size'
> should be subject to some user limits. Anyways, mounting inside
> user namespaces is  a different discussion.
>
> So, if a filesystem has to be setup for exclusive use by an application,
> then different mount options can be used for that filesystem.
>

Any further comments?

Cc'ing Andrea as we had discussed this requirement for the Database.