From: Andrea Arcangeli <aarcange@redhat.com>
To: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Mike Rapoport <rapoport@il.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Mike Rapoport <mike.rapoport@gmail.com>
Subject: Re: [PATCH 0/5] userfaultfd: extension for non cooperative uffd usage
Date: Fri, 22 Apr 2016 12:05:57 -0400 [thread overview]
Message-ID: <20160422160557.GB4282@redhat.com> (raw)
In-Reply-To: <57174F90.7080109@virtuozzo.com>
Hello Pavel and Mike,
On Wed, Apr 20, 2016 at 12:44:48PM +0300, Pavel Emelyanov wrote:
> On 03/20/2016 03:42 PM, Mike Rapoport wrote:
> > Hi,
> >
> > This set is to address the issues that appear in userfaultfd usage
> > scenarios when the task monitoring the uffd and the mm-owner do not
> > cooperate to each other on VM changes such as remaps, madvises and
> > fork()-s.
> >
> > The pacthes are essentially the same as in the prevoious respin (1),
> > they've just been rebased on the current tree.
Thanks for the rebasing and the submit of these new features!
>
> Hi, Andrea.
>
> Hopefully one day after LSFMM is good time to try to get a bit of
> your attention to this set :)
Yes, at first glance this patchset looks fine. In fact I already
merged it in my tree at the time of last post. Just I didn't have much
time to review it in detail yet as I did with the wrprotect tracking
one, this is why I didn't answer yet, sorry.
As said I already reviewed the wrprotect tracking feature in detail
and it requires a few (but non trivial) fixes and I was planning to
fix that part first as the developer who sent the first implementation
a few months ago got busy with something else. But until those bugs
gets fixed I cannot ship it in my tree, nor in the way to -mm.
The other main reason of the delay is that I got sidetracked by other
issues (one internal) and the other notable one is the failure in
postcopy caused by the new THP refcounting introduced in 4.5 with THP
enabled, which apparently isn't the huge zeropage (tested with
use_zero_page = 0) nor the MADV_DONTNEED. I'm also unconvinced it's a
bug only in the userfaultfd interaction with the new THP refcounting,
perhaps it's something more generic that just happen to be reproduced
more easily by the heavy postcopy load, which makes it even more high
priority to track that down.
I'm afraid until that regression is fixed, I'll have to concentrate on
fixing that. At least I found a way to reproduce faster so I'm
optimistic it won't take long ;).
Andrea
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prev parent reply other threads:[~2016-04-22 16:06 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-20 12:42 [PATCH 0/5] userfaultfd: extension for non cooperative uffd usage Mike Rapoport
2016-03-20 12:42 ` [PATCH 1/5] uffd: Split the find_userfault() routine Mike Rapoport
2016-03-20 12:42 ` [PATCH 2/5] uffd: Add ability to report non-PF events from uffd descriptor Mike Rapoport
2016-03-20 12:42 ` [PATCH 3/5] uffd: Add fork() event Mike Rapoport
2016-03-20 12:53 ` kbuild test robot
2016-03-20 12:42 ` [PATCH 4/5] uffd: Add mremap() event Mike Rapoport
2016-03-20 12:42 ` [PATCH 5/5] uffd: Add madvise() event for MADV_DONTNEED request Mike Rapoport
2016-03-21 9:54 ` [PATCH 0/5] userfaultfd: extension for non cooperative uffd usage Pavel Emelyanov
2016-04-06 6:14 ` Mike Rapoport
2016-04-20 9:44 ` Pavel Emelyanov
2016-04-22 16:05 ` Andrea Arcangeli [this message]
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