From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, linux-api@vger.kernel.org,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Michal Hocko <mhocko@suse.com>, Aaron Lu <aaron.lu@intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [RFC PATCH 1/1] mm/mremap: add MREMAP_MIRROR flag for existing mirroring functionality
Date: Fri, 7 Jul 2017 13:23:24 +0300 [thread overview]
Message-ID: <20170707102324.kfihkf72sjcrtn5b@node.shutemov.name> (raw)
In-Reply-To: <1499357846-7481-2-git-send-email-mike.kravetz@oracle.com>
On Thu, Jul 06, 2017 at 09:17:26AM -0700, Mike Kravetz wrote:
> The mremap system call has the ability to 'mirror' parts of an existing
> mapping. To do so, it creates a new mapping that maps the same pages as
> the original mapping, just at a different virtual address. This
> functionality has existed since at least the 2.6 kernel.
>
> This patch simply adds a new flag to mremap which will make this
> functionality part of the API. It maintains backward compatibility with
> the existing way of requesting mirroring (old_size == 0).
>
> If this new MREMAP_MIRROR flag is specified, then new_size must equal
> old_size. In addition, the MREMAP_MAYMOVE flag must be specified.
The patch breaks important invariant that anon page can be mapped into a
process only once.
What is going to happen to mirrored after CoW for instance?
In my opinion, it shouldn't be allowed for anon/private mappings at least.
And with this limitation, I don't see much sense in the new interface --
just create mirror by mmap()ing the file again.
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2017-07-07 10:23 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-06 16:17 [RFC PATCH 0/1] mm/mremap: add MREMAP_MIRROR flag Mike Kravetz
2017-07-06 16:17 ` [RFC PATCH 1/1] mm/mremap: add MREMAP_MIRROR flag for existing mirroring functionality Mike Kravetz
2017-07-07 8:45 ` Anshuman Khandual
2017-07-07 17:14 ` Mike Kravetz
2017-07-09 7:23 ` Anshuman Khandual
2017-07-07 10:23 ` Kirill A. Shutemov [this message]
2017-07-07 17:29 ` Mike Kravetz
2017-07-07 17:45 ` Kirill A. Shutemov
2017-07-07 18:09 ` Mike Kravetz
2017-07-09 7:32 ` Anshuman Khandual
2017-07-10 16:22 ` Vlastimil Babka
2017-07-10 17:22 ` Mike Kravetz
2017-07-11 12:36 ` Michal Hocko
2017-07-11 18:23 ` Mike Kravetz
2017-07-11 21:02 ` Andrea Arcangeli
2017-07-11 21:57 ` Mike Kravetz
2017-07-11 23:31 ` Andrea Arcangeli
2017-07-12 11:46 ` Michal Hocko
2017-07-12 16:55 ` Mike Kravetz
2017-07-13 6:16 ` Michal Hocko
2017-07-13 16:01 ` Mike Kravetz
2017-07-13 16:30 ` Andrea Arcangeli
2017-07-13 18:11 ` Mike Kravetz
2017-07-13 20:33 ` Andrea Arcangeli
2017-07-07 8:19 ` [RFC PATCH 0/1] mm/mremap: add MREMAP_MIRROR flag Anshuman Khandual
2017-07-07 17:04 ` Mike Kravetz
2017-07-07 11:03 ` Anshuman Khandual
2017-07-07 17:12 ` Mike Kravetz
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