From: Wanpeng Li <liwanp@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andi Kleen <andi@firstfloor.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
Hillf Danton <dhillf@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/6] mm/hugetlb: gigantic hugetlb page pools shrink supporting
Date: Wed, 17 Apr 2013 09:19:43 +0800 [thread overview]
Message-ID: <20130417011943.GA7901@hacker.(null)> (raw)
In-Reply-To: <20130417011144.GA20835@dhcp22.suse.cz>
On Tue, Apr 16, 2013 at 06:11:44PM -0700, Michal Hocko wrote:
>On Wed 17-04-13 08:36:28, Wanpeng Li wrote:
>> Changelog:
>> * add comments from Andi which indicate shrink gigantic hugetlb page pools make
>> sense to patchset description.
>>
>> order >= MAX_ORDER pages are only allocated at boot stage using the
>> bootmem allocator with the "hugepages=xxx" option. These pages are never
>> free after boot by default since it would be a one-way street(>= MAX_ORDER
>> pages cannot be allocated later), but if administrator confirm not to
>> use these gigantic pages any more, these pinned pages will waste memory
>> since other users can't grab free pages from gigantic hugetlb pool even
>> if OOM, it's not flexible. The patchset add hugetlb gigantic page pools
>> shrink supporting. Administrator can enable knob exported in sysctl to
>> permit to shrink gigantic hugetlb pool.
>>
>> http://marc.info/?l=linux-mm&m=136578016214512&w=2
>> Andi thinks this idea make sense since he is working on a new patchkit to
>> allocate GB pages from CMA. With that freeing actually makes sense, as the
>> pages can be reallocated.
>
>But that is not implemented yet...
>
>>
>> Testcase:
>> boot: hugepagesz=1G hugepages=10
>>
>> [root@localhost hugepages]# free -m
>> total used free shared buffers cached
>> Mem: 36269 10836 25432 0 11 288
>> -/+ buffers/cache: 10537 25732
>> Swap: 35999 0 35999
>> [root@localhost hugepages]# echo 0 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
>> -bash: echo: write error: Invalid argument
>> [root@localhost hugepages]# echo 1 > /proc/sys/vm/hugetlb_shrink_gigantic_pool
>
>I have asked that already but it didn't get answered. What is the reason
>for an explicit knob to enable this? It just adds an additional code and
>it doesn't make much sense to me to be honest.
Make sense to me, it seems that I don't need to add this redundant knob and
just let gigantic hugetlb pages pool shrink awareness after Andi's patchkit
merged. ;-)
Regards,
Wanpeng Li
>
>[...]
>--
>Michal Hocko
>SUSE Labs
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next prev parent reply other threads:[~2013-04-17 1:19 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-17 0:36 [PATCH v2 0/6] mm/hugetlb: gigantic hugetlb page pools shrink supporting Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 0:36 ` [PATCH v2 1/6] mm/hugetlb: introduce new sysctl knob which control gigantic page pools shrinking Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 0:36 ` [PATCH v2 2/6] mm/hugetlb: update_and_free_page gigantic pages awareness Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 0:36 ` [PATCH v2 3/6] mm/hugetlb: enable gigantic hugetlb page pools shrinking Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 0:36 ` [PATCH v2 4/6] mm/hugetlb: use already exist huge_page_order() instead of h->order Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 0:36 ` [PATCH v2 5/6] mm/hugetlb: remove redundant hugetlb_prefault Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 0:36 ` [PATCH v2 6/6] mm/hugetlb: use already exist interface huge_page_shift Wanpeng Li
2013-04-17 0:36 ` Wanpeng Li
2013-04-17 1:11 ` [PATCH v2 0/6] mm/hugetlb: gigantic hugetlb page pools shrink supporting Michal Hocko
2013-04-17 1:11 ` Michal Hocko
2013-04-17 1:19 ` Wanpeng Li [this message]
2013-04-17 1:19 ` Wanpeng Li
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