From: Matthew Wilcox <willy@infradead.org>
To: David Hildenbrand <david@redhat.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>,
"Longpeng (Mike,
Cloud Infrastructure Service Product Dept.)"
<longpeng2@huawei.com>,
Steven Sistare <steven.sistare@oracle.com>,
Anthony Yznaga <anthony.yznaga@oracle.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"Gonglei (Arei)" <arei.gonglei@huawei.com>
Subject: Re: [RFC PATCH 0/5] madvise MADV_DOEXEC
Date: Mon, 16 Aug 2021 15:40:56 +0100 [thread overview]
Message-ID: <YRp4+EmohNoxzv2x@casper.infradead.org> (raw)
In-Reply-To: <3ce1f52f-d84d-49ba-c027-058266e16d81@redhat.com>
On Mon, Aug 16, 2021 at 04:33:09PM +0200, David Hildenbrand wrote:
> > > I did not follow why we have to play games with MAP_PRIVATE, and having
> > > private anonymous pages shared between processes that don't COW, introducing
> > > new syscalls etc.
> >
> > It's not about SHMEM, it's about file-backed pages on regular
> > filesystems. I don't want to have XFS, ext4 and btrfs all with their
> > own implementations of ARCH_WANT_HUGE_PMD_SHARE.
>
> Let me ask this way: why do we have to play such games with MAP_PRIVATE?
Are you referring to this?
: Mappings within this address range behave as if they were shared
: between threads, so a write to a MAP_PRIVATE mapping will create a
: page which is shared between all the sharers.
If so, that's a misunderstanding, because there are no games being played.
What Khalid's saying there is that because the page tables are already
shared for that range of address space, the COW of a MAP_PRIVATE will
create a new page, but that page will be shared between all the sharers.
The second write to a MAP_PRIVATE page (by any of the sharers) will not
create a COW situation. Just like if all the sharers were threads of
the same process.
next prev parent reply other threads:[~2021-08-16 14:42 UTC|newest]
Thread overview: 115+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 17:11 [RFC PATCH 0/5] madvise MADV_DOEXEC Anthony Yznaga
2020-07-27 17:07 ` Eric W. Biederman
2020-07-27 17:07 ` Eric W. Biederman
2020-07-27 18:00 ` Steven Sistare
2020-07-28 13:40 ` Christian Brauner
2020-07-27 17:11 ` [RFC PATCH 1/5] elf: reintroduce using MAP_FIXED_NOREPLACE for elf executable mappings Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 2/5] mm: do not assume only the stack vma exists in setup_arg_pages() Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 3/5] mm: introduce VM_EXEC_KEEP Anthony Yznaga
2020-07-28 13:38 ` Eric W. Biederman
2020-07-28 13:38 ` Eric W. Biederman
2020-07-28 17:44 ` Anthony Yznaga
2020-07-29 13:52 ` Kirill A. Shutemov
2020-07-29 23:20 ` Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 4/5] exec, elf: require opt-in for accepting preserved mem Anthony Yznaga
2020-07-27 17:11 ` [RFC PATCH 5/5] mm: introduce MADV_DOEXEC Anthony Yznaga
2020-07-28 13:22 ` Kirill Tkhai
2020-07-28 14:06 ` Steven Sistare
2020-07-28 11:34 ` [RFC PATCH 0/5] madvise MADV_DOEXEC Kirill Tkhai
2020-07-28 17:28 ` Anthony Yznaga
2020-07-28 14:23 ` Andy Lutomirski
2020-07-28 14:30 ` Steven Sistare
2020-07-30 15:22 ` Matthew Wilcox
2020-07-30 15:27 ` Christian Brauner
2020-07-30 15:34 ` Matthew Wilcox
2020-07-30 15:54 ` Christian Brauner
2020-07-31 9:12 ` Stefan Hajnoczi
2020-07-31 9:12 ` Stefan Hajnoczi
2020-07-30 15:59 ` Steven Sistare
2020-07-30 17:12 ` Matthew Wilcox
2020-07-30 17:35 ` Steven Sistare
2020-07-30 17:49 ` Matthew Wilcox
2020-07-30 18:27 ` Steven Sistare
2020-07-30 21:58 ` Eric W. Biederman
2020-07-30 21:58 ` Eric W. Biederman
2020-07-31 14:57 ` Steven Sistare
2020-07-31 15:27 ` Matthew Wilcox
2020-07-31 16:11 ` Steven Sistare
2020-07-31 16:56 ` Jason Gunthorpe
2020-07-31 17:15 ` Steven Sistare
2020-07-31 17:48 ` Jason Gunthorpe
2020-07-31 17:55 ` Steven Sistare
2020-08-03 8:32 ` David Laight
2020-08-03 8:32 ` David Laight
2020-07-31 17:23 ` Matthew Wilcox
2020-08-03 15:28 ` Eric W. Biederman
2020-08-03 15:28 ` Eric W. Biederman
2020-08-03 15:42 ` James Bottomley
2020-08-03 15:42 ` James Bottomley
2020-08-03 20:03 ` Steven Sistare
2020-08-04 8:44 ` David Laight
2020-08-04 8:44 ` David Laight
2020-08-04 11:13 ` Matthew Wilcox
2020-08-04 11:13 ` Matthew Wilcox
2020-08-03 19:29 ` Steven Sistare
2020-07-31 19:41 ` Steven Sistare
2021-07-08 9:52 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-07-08 9:52 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-07-08 12:48 ` Steven Sistare
2021-07-08 12:48 ` Steven Sistare
2021-07-12 1:05 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-07-12 1:05 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-07-12 1:30 ` Matthew Wilcox
2021-07-12 1:30 ` Matthew Wilcox
2021-07-13 0:57 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-07-13 0:57 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-13 19:49 ` Khalid Aziz
2021-08-13 19:49 ` Khalid Aziz
2021-08-14 20:07 ` David Laight
2021-08-14 20:07 ` David Laight
2021-08-16 0:26 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-16 0:26 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-16 8:07 ` David Laight
2021-08-16 8:07 ` David Laight
2021-08-16 6:54 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-16 6:54 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-16 8:02 ` David Hildenbrand
2021-08-16 8:02 ` David Hildenbrand
2021-08-16 12:07 ` Matthew Wilcox
2021-08-16 12:07 ` Matthew Wilcox
2021-08-16 12:20 ` David Hildenbrand
2021-08-16 12:20 ` David Hildenbrand
2021-08-16 12:42 ` David Hildenbrand
2021-08-16 12:42 ` David Hildenbrand
2021-08-16 12:46 ` Matthew Wilcox
2021-08-16 12:46 ` Matthew Wilcox
2021-08-16 13:24 ` David Hildenbrand
2021-08-16 13:24 ` David Hildenbrand
2021-08-16 13:32 ` Matthew Wilcox
2021-08-16 13:32 ` Matthew Wilcox
2021-08-16 14:10 ` David Hildenbrand
2021-08-16 14:10 ` David Hildenbrand
2021-08-16 14:27 ` Matthew Wilcox
2021-08-16 14:27 ` Matthew Wilcox
2021-08-16 14:33 ` David Hildenbrand
2021-08-16 14:33 ` David Hildenbrand
2021-08-16 14:40 ` Matthew Wilcox [this message]
2021-08-16 14:40 ` Matthew Wilcox
2021-08-16 15:01 ` David Hildenbrand
2021-08-16 15:01 ` David Hildenbrand
2021-08-16 15:59 ` Matthew Wilcox
2021-08-16 15:59 ` Matthew Wilcox
2021-08-16 16:06 ` Khalid Aziz
2021-08-16 16:06 ` Khalid Aziz
2021-08-16 16:15 ` Matthew Wilcox
2021-08-16 16:15 ` Matthew Wilcox
2021-08-16 16:13 ` David Hildenbrand
2021-08-16 16:13 ` David Hildenbrand
2021-08-16 12:27 ` [private] " David Hildenbrand
2021-08-16 12:27 ` David Hildenbrand
2021-08-16 12:30 ` David Hildenbrand
2021-08-16 12:30 ` David Hildenbrand
2021-08-17 0:47 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-17 0:47 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-08-17 0:55 ` Matthew Wilcox
2021-08-17 0:55 ` Matthew Wilcox
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