From: Andrea Arcangeli <aarcange@redhat.com>
To: Daniel Colascione <dancol@google.com>
Cc: Andy Lutomirski <luto@kernel.org>, Jann Horn <jannh@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Lokesh Gidra <lokeshgidra@google.com>,
Nick Kralevich <nnk@google.com>, Nosh Minwalla <nosh@google.com>,
Tim Murray <timmurray@google.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Linux API <linux-api@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/7] Add a UFFD_SECURE flag to the userfaultfd API.
Date: Wed, 23 Oct 2019 20:23:12 -0400 [thread overview]
Message-ID: <20191024002312.GB433@redhat.com> (raw)
In-Reply-To: <CAKOZuetKkM=PK2QA8LdXwM8cM8qJvFu4u5bjePWai3XRnHe-pA@mail.gmail.com>
On Wed, Oct 23, 2019 at 01:05:47PM -0700, Daniel Colascione wrote:
> This is a debate that won't get resolved here. A ton of work has gone
> into namespaces, migration, various cgroup things, and so on, and I
> don't see that work getting torn out.
This is precisely why I thought it was a good idea to support the
non-cooperative use case too even though we had no immediate use for
it.
> Sure they can. Can't we stick processes in a memcg and set a
> memory.high threshold beyond which threads in that cgroup will enter
> direct reclaim on page allocations? I'd call that throttling.
The uffd-wp solution during the throttling can resolve a wrprotect
fault in the parent for every 4k page that has been written to disk
and it'll prioritize writing to disk those userfaults that are
currently blocked. I don't see how you could reach an equivalent
optimal runtime without uffd-wp and just with memcg because the
snapshot process won't have a clue which pages are been duped by the
COWs. The uffd-wp by avoding fork will also avoid more expensive MM
switches during the snapshot.
> This issue *has* to get fixed one way or another.
Sure.
next prev parent reply other threads:[~2019-10-24 0:23 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-12 19:15 [PATCH 0/7] Harden userfaultfd Daniel Colascione
2019-10-12 19:15 ` [PATCH 1/7] Add a new flags-accepting interface for anonymous inodes Daniel Colascione
2019-10-14 4:26 ` kbuild test robot
2019-10-14 15:38 ` Jann Horn
2019-10-14 18:15 ` Daniel Colascione
2019-10-14 18:30 ` Jann Horn
2019-10-15 8:08 ` Christoph Hellwig
2019-10-12 19:15 ` [PATCH 2/7] Add a concept of a "secure" anonymous file Daniel Colascione
2019-10-14 3:01 ` kbuild test robot
2019-10-15 8:08 ` Christoph Hellwig
2019-10-12 19:15 ` [PATCH 3/7] Add a UFFD_SECURE flag to the userfaultfd API Daniel Colascione
2019-10-12 23:10 ` Andy Lutomirski
2019-10-13 0:51 ` Daniel Colascione
2019-10-13 1:14 ` Andy Lutomirski
2019-10-13 1:38 ` Daniel Colascione
2019-10-14 16:04 ` Jann Horn
2019-10-23 19:09 ` Andrea Arcangeli
2019-10-23 19:21 ` Andy Lutomirski
2019-10-23 21:16 ` Andrea Arcangeli
2019-10-23 21:25 ` Andy Lutomirski
2019-10-23 22:41 ` Andrea Arcangeli
2019-10-23 23:01 ` Andy Lutomirski
2019-10-23 23:27 ` Andrea Arcangeli
2019-10-23 20:05 ` Daniel Colascione
2019-10-24 0:23 ` Andrea Arcangeli [this message]
2019-10-23 20:15 ` Linus Torvalds
2019-10-24 9:02 ` Mike Rapoport
2019-10-24 15:10 ` Andrea Arcangeli
2019-10-25 20:12 ` Mike Rapoport
2019-10-22 21:27 ` Daniel Colascione
2019-10-23 4:11 ` Andy Lutomirski
2019-10-23 7:29 ` Cyrill Gorcunov
2019-10-23 12:43 ` Mike Rapoport
2019-10-23 17:13 ` Andy Lutomirski
2019-10-12 19:15 ` [PATCH 4/7] Teach SELinux about a new userfaultfd class Daniel Colascione
2019-10-12 23:08 ` Andy Lutomirski
2019-10-13 0:11 ` Daniel Colascione
2019-10-13 0:46 ` Andy Lutomirski
2019-10-12 19:16 ` [PATCH 5/7] Let userfaultfd opt out of handling kernel-mode faults Daniel Colascione
2019-10-12 19:16 ` [PATCH 6/7] Allow users to require UFFD_SECURE Daniel Colascione
2019-10-12 23:12 ` Andy Lutomirski
2019-10-12 19:16 ` [PATCH 7/7] Add a new sysctl for limiting userfaultfd to user mode faults Daniel Colascione
2019-10-16 0:02 ` [PATCH 0/7] Harden userfaultfd James Morris
2019-11-15 15:09 ` Stephen Smalley
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