All of lore.kernel.org
 help / color / mirror / Atom feed
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>

[-- Attachment #1: Type: text/plain, Size: 1313 bytes --]

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

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 854 bytes --]

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=19612088-4856-4BE9-A731-BB903511F352@nvidia.com \
    --to=ziy@nvidia.com \
    --cc=aarcange@redhat.com \
    --cc=akpm@linux-foundation.org \
    --cc=dbueso@suse.de \
    --cc=jgg@ziepe.ca \
    --cc=joao.m.martins@oracle.com \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mike.kravetz@oracle.com \
    --cc=osalvador@suse.de \
    --cc=stable@vger.kernel.org \
    --cc=willy@infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.