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From: Mike Kravetz <mike.kravetz@oracle.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 0/4] hugetlbfs: optionally reserve all fs pages at mount time
Date: Fri, 06 Mar 2015 14:30:37 -0800	[thread overview]
Message-ID: <54FA2A8D.5090509@oracle.com> (raw)
In-Reply-To: <87lhj9ai5u.fsf@tassilo.jf.intel.com>

On 03/06/2015 02:13 PM, Andi Kleen wrote:
> Mike Kravetz <mike.kravetz@oracle.com> writes:
>
>> hugetlbfs allocates huge pages from the global pool as needed.  Even if
>> the global pool contains a sufficient number pages for the filesystem
>> size at mount time, those global pages could be grabbed for some other
>> use.  As a result, filesystem huge page allocations may fail due to lack
>> of pages.
>
>
> What's the difference of this new option to simply doing
>
> mount -t hugetlbfs none /huge
> echo XXX > /proc/sys/vm/nr_hugepages

In the above sequence, it is still possible for another user/application
to allocate some (or all) of the XXX huge pages.  There is no guarantee
that users of the filesystem will get all XXX pages.

I see the use of the reserve option to be:
# Make sure there are XXX huge pages in the global pool
echo XXX > /proc/sys/vm/nr_hugepages
# Mount/create the filesystem and reserve XXX huge pages
mount -t hugetlbfs -o size=XXX,reserve=XXX none /huge

If the mount is successful, then users of the filesystem know their are
XXX huge pages available for their use.

-- 
Mike Kravetz

      reply	other threads:[~2015-03-06 22:31 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-04  1:21 Mike Kravetz
2015-03-04  1:21 ` [PATCH 1/4] hugetlbfs: add reserved mount fields to subpool structure Mike Kravetz
2015-03-04  1:21 ` [PATCH 2/4] hugetlbfs: coordinate global and subpool reserve accounting Mike Kravetz
2015-03-04  1:21 ` [PATCH 3/4] hugetlbfs: accept subpool reserved option and setup accordingly Mike Kravetz
2015-03-04  1:21 ` [PATCH 4/4] hugetlbfs: document reserved mount option Mike Kravetz
2015-03-04  5:49 ` [PATCH 0/4] hugetlbfs: optionally reserve all fs pages at mount time David Rientjes
2015-03-04 17:21   ` Mike Kravetz
2015-03-06 22:13 ` Andi Kleen
2015-03-06 22:30   ` Mike Kravetz [this message]

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