From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>,
akpm@linux-foundation.org, Michal Hocko <mhocko@kernel.org>,
mpe@ellerman.id.au, paulus@samba.org,
David Gibson <david@gibson.dropbear.id.au>
Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V5 1/3] mm: Add get_user_pages_cma_migrate
Date: Thu, 20 Dec 2018 10:52:09 +0530 [thread overview]
Message-ID: <b316eb1c-36dc-49e0-f46f-e610f29b6058@linux.ibm.com> (raw)
In-Reply-To: <e9c9b68a-a31b-ab59-902a-73401a89f72a@ozlabs.ru>
On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote:
>
>
> On 19/12/2018 14:40, Aneesh Kumar K.V wrote:
>> This helper does a get_user_pages_fast and if it find pages in the CMA area
>> it will try to migrate them before taking page reference. This makes sure that
>> we don't keep non-movable pages (due to page reference count) in the CMA area.
>> Not able to move pages out of CMA area result in CMA allocation failures.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>
.....
>> + * We did migrate all the pages, Try to get the page references again
>> + * migrating any new CMA pages which we failed to isolate earlier.
>> + */
>> + drain_allow = true;
>> + goto get_user_again;
>
>
> So it is possible to have pages pinned, then successfully migrated
> (migrate_pages() returned 0), then pinned again, then some pages may end
> up in CMA again and migrate again and nothing seems to prevent this loop
> from being endless. What do I miss?
>
pages used as target page for migration won't be allocated from CMA region.
-aneesh
next prev parent reply other threads:[~2018-12-20 5:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-19 3:40 [PATCH V5 0/3] mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region Aneesh Kumar K.V
2018-12-19 3:40 ` [PATCH V5 1/3] mm: Add get_user_pages_cma_migrate Aneesh Kumar K.V
2018-12-20 4:19 ` Alexey Kardashevskiy
2018-12-20 5:22 ` Aneesh Kumar K.V [this message]
2018-12-20 5:48 ` Alexey Kardashevskiy
2018-12-20 5:52 ` Aneesh Kumar K.V
2018-12-20 6:20 ` Alexey Kardashevskiy
2018-12-20 6:26 ` Aneesh Kumar K.V
2018-12-20 4:28 ` Alexey Kardashevskiy
2018-12-19 3:40 ` [PATCH V5 2/3] powerpc/mm/iommu: Allow migration of cma allocated pages during mm_iommu_get Aneesh Kumar K.V
2018-12-20 5:16 ` Alexey Kardashevskiy
2018-12-19 3:40 ` [PATCH V5 3/3] powerpc/mm/iommu: Allow large IOMMU page size only for hugetlb backing Aneesh Kumar K.V
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