From: Zi Yan <ziy@nvidia.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
Davidlohr Bueso <dbueso@suse.de>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
Joao Martins <joao.m.martins@oracle.com>,
<stable@vger.kernel.org>
Subject: Re: [PATCH 1/2] hugetlb: fix update_and_free_page contig page struct assumption
Date: Thu, 18 Feb 2021 12:27:58 -0500 [thread overview]
Message-ID: <19612088-4856-4BE9-A731-BB903511F352@nvidia.com> (raw)
In-Reply-To: <20210218172500.GA4718@ziepe.ca>
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On 18 Feb 2021, at 12:25, Jason Gunthorpe wrote:
> On Thu, Feb 18, 2021 at 02:45:54PM +0000, Matthew Wilcox wrote:
>> On Wed, Feb 17, 2021 at 11:02:52AM -0800, Andrew Morton wrote:
>>> On Wed, 17 Feb 2021 10:49:25 -0800 Mike Kravetz <mike.kravetz@oracle.com> wrote:
>>>> page structs are not guaranteed to be contiguous for gigantic pages. The
>>>
>>> June 2014. That's a long lurk time for a bug. I wonder if some later
>>> commit revealed it.
>>
>> I would suggest that gigantic pages have not seen much use. Certainly
>> performance with Intel CPUs on benchmarks that I've been involved with
>> showed lower performance with 1GB pages than with 2MB pages until quite
>> recently.
>
> I suggested in another thread that maybe it is time to consider
> dropping this "feature"
You mean dropping gigantic page support in hugetlb?
>
> If it has been slightly broken for 7 years it seems a good bet it
> isn't actually being used.
>
> The cost to fix GUP to be compatible with this will hurt normal
> GUP performance - and again, that nobody has hit this bug in GUP
> further suggests the feature isn't used..
A easy fix might be to make gigantic hugetlb page depends on
CONFIG_SPARSEMEM_VMEMMAP, which guarantee all struct pages are contiguous.
—
Best Regards,
Yan Zi
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next prev parent reply other threads:[~2021-02-18 19:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 18:49 [PATCH 1/2] hugetlb: fix update_and_free_page contig page struct assumption Mike Kravetz
2021-02-17 18:49 ` [PATCH 2/2] hugetlb: fix copy_huge_page_from_user " Mike Kravetz
2021-02-17 19:02 ` [PATCH 1/2] hugetlb: fix update_and_free_page " Andrew Morton
2021-02-17 19:38 ` Mike Kravetz
2021-02-18 14:45 ` Matthew Wilcox
2021-02-18 17:25 ` Jason Gunthorpe
2021-02-18 17:27 ` Zi Yan [this message]
2021-02-18 17:32 ` Jason Gunthorpe
2021-02-18 17:40 ` Zi Yan
2021-02-18 17:51 ` Mike Kravetz
2021-02-18 18:50 ` Zi Yan
2021-02-18 17:34 ` Mike Kravetz
2021-02-18 21:43 ` Mike Kravetz
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