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From: Andrea Arcangeli <aarcange@redhat.com>
To: zhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	qemu-devel@nongnu.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Andres Lagar-Cavilla <andreslc@google.com>,
	Dave Hansen <dave@sr71.net>, Paolo Bonzini <pbonzini@redhat.com>,
	Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
	Andy Lutomirski <luto@amacapital.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Sasha Levin <sasha.levin@oracle.com>,
	Hugh Dickins <hughd@google.com>,
	Peter Feiner <pfeiner@google.com>,
	Christopher Covington <cov@codeaurora.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Android Kernel Team <kernel-team@android.com>,
	Robert Love <rlove@google.com>,
	Dmitry Adamushko <dmitry.adamushko@gmail.com>,
	Neil Brown <neilb@suse.de>, Mike Hommey <mh@glandium.org>,
	Taras Glek <tglek@mozilla.com>, Jan Kara <jack@suse.cz>,
	KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
	Michel Lespinasse <walken@google.com>,
	Minchan Kim <minchan@kernel.org>,
	Keith Packard <keithp@keithp.com>,
	"Huangpeng (Peter)" <peter.huangpeng@huawei.com>,
	Isaku Yamahata <yamahata@valinux.co.jp>,
	Anthony Liguori <anthony@codemonkey.ws>,
	Stefan Hajnoczi <stefanha@gmail.com>,
	Wenchao Xia <wenchaoqemu@gmail.com>,
	Andrew Jones <drjones@redhat.com>,
	Juan Quintela <quintela@redhat.com>
Subject: Re: [PATCH 00/17] RFC: userfault v2
Date: Thu, 20 Nov 2014 18:38:33 +0100	[thread overview]
Message-ID: <20141120173833.GG803@redhat.com> (raw)
In-Reply-To: <546D57E5.3080803@huawei.com>

Hi,

On Thu, Nov 20, 2014 at 10:54:29AM +0800, zhanghailiang wrote:
> Yes, you are right. This is what i really want, bypass all non-present faults
> and only track strict wrprotect faults. ;)
> 
> So, do you plan to support that in the userfault API?

Yes I think it's good idea to support wrprotect/COW faults too.

I just wanted to understand if there was any other reason why you
needed only wrprotect faults, because the non-present faults didn't
look like a big performance concern if they triggered in addition to
wrprotect faults, but it's certainly ok to optimize them away so it's
fully optimal.

All it takes to differentiate the behavior should be one more bit
during registration so you can select non-present, wrprotect faults or
both. postcopy live migration would select only non-present faults,
postcopy live snapshot would select only wrprotect faults, anything
like distributed shared memory supporting shared readonly access and
exclusive write access, would select both flags.

I just sent an (unfortunately) longish but way more detailed email
about live snapshotting with userfaultfd but I just wanted to give a
shorter answer here too :).

Thanks,
Andrea

  reply	other threads:[~2014-11-20 17:39 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-03 17:07 [PATCH 00/17] RFC: userfault v2 Andrea Arcangeli
2014-10-03 17:07 ` [PATCH 01/17] mm: gup: add FOLL_TRIED Andrea Arcangeli
2014-10-03 18:15   ` Linus Torvalds
2014-10-03 20:55     ` Paolo Bonzini
2014-10-03 17:07 ` [PATCH 02/17] mm: gup: add get_user_pages_locked and get_user_pages_unlocked Andrea Arcangeli
2014-10-03 17:07 ` [PATCH 03/17] mm: gup: use get_user_pages_unlocked within get_user_pages_fast Andrea Arcangeli
2014-10-03 17:07 ` [PATCH 04/17] mm: gup: make get_user_pages_fast and __get_user_pages_fast latency conscious Andrea Arcangeli
2014-10-03 18:23   ` Linus Torvalds
2014-10-06 14:14     ` Andrea Arcangeli
2014-10-03 17:07 ` [PATCH 05/17] mm: gup: use get_user_pages_fast and get_user_pages_unlocked Andrea Arcangeli
2014-10-03 17:07 ` [PATCH 06/17] kvm: Faults which trigger IO release the mmap_sem Andrea Arcangeli
2014-10-03 17:07 ` [PATCH 07/17] mm: madvise MADV_USERFAULT: prepare vm_flags to allow more than 32bits Andrea Arcangeli
2014-10-07  9:03   ` Kirill A. Shutemov
2014-11-06 20:08   ` Konstantin Khlebnikov
2014-10-03 17:07 ` [PATCH 08/17] mm: madvise MADV_USERFAULT Andrea Arcangeli
2014-10-03 23:13   ` Mike Hommey
2014-10-06 17:24     ` Andrea Arcangeli
2014-10-07 10:36   ` Kirill A. Shutemov
2014-10-07 10:46     ` Dr. David Alan Gilbert
2014-10-07 10:52       ` [Qemu-devel] " Kirill A. Shutemov
2014-10-07 11:01         ` Dr. David Alan Gilbert
2014-10-07 11:30           ` Kirill A. Shutemov
2014-10-07 13:24     ` Andrea Arcangeli
2014-10-07 15:21       ` Kirill A. Shutemov
2014-10-03 17:07 ` [PATCH 09/17] mm: PT lock: export double_pt_lock/unlock Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 10/17] mm: rmap preparation for remap_anon_pages Andrea Arcangeli
2014-10-03 18:31   ` Linus Torvalds
2014-10-06  8:55     ` Dr. David Alan Gilbert
2014-10-06 16:41       ` Andrea Arcangeli
2014-10-07 12:47         ` Linus Torvalds
2014-10-07 14:19           ` Andrea Arcangeli
2014-10-07 15:52             ` Andrea Arcangeli
2014-10-07 15:54               ` Andy Lutomirski
2014-10-07 16:13               ` Peter Feiner
2014-10-07 16:56             ` Linus Torvalds
2014-10-07 17:07           ` Dr. David Alan Gilbert
2014-10-07 17:14             ` Paolo Bonzini
2014-10-07 17:25               ` Dr. David Alan Gilbert
2014-10-07 11:10   ` [Qemu-devel] " Kirill A. Shutemov
2014-10-07 13:37     ` Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 11/17] mm: swp_entry_swapcount Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 12/17] mm: sys_remap_anon_pages Andrea Arcangeli
2014-10-04 13:13   ` Andi Kleen
2014-10-06 17:00     ` Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 13/17] waitqueue: add nr wake parameter to __wake_up_locked_key Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 14/17] userfaultfd: add new syscall to provide memory externalization Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 15/17] userfaultfd: make userfaultfd_write non blocking Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 16/17] powerpc: add remap_anon_pages and userfaultfd Andrea Arcangeli
2014-10-03 17:08 ` [PATCH 17/17] userfaultfd: implement USERFAULTFD_RANGE_REGISTER|UNREGISTER Andrea Arcangeli
2014-10-27  9:32 ` [PATCH 00/17] RFC: userfault v2 zhanghailiang
2014-10-29 17:46   ` Andrea Arcangeli
2014-10-29 17:56     ` [Qemu-devel] " Peter Maydell
2014-11-21 20:14       ` Andrea Arcangeli
2014-11-21 23:05         ` Peter Maydell
2014-11-25 19:45           ` Andrea Arcangeli
2014-10-30 11:31     ` zhanghailiang
2014-10-30 12:49       ` Dr. David Alan Gilbert
2014-10-31  1:26         ` zhanghailiang
2014-11-19 18:49           ` Andrea Arcangeli
2014-11-20  2:54             ` zhanghailiang
2014-11-20 17:38               ` Andrea Arcangeli [this message]
2014-11-21  7:19                 ` zhanghailiang
2014-10-31  2:23       ` Peter Feiner
2014-10-31  3:29         ` zhanghailiang
2014-10-31  4:38           ` zhanghailiang
2014-10-31  5:17             ` Andres Lagar-Cavilla
2014-10-31  8:11               ` zhanghailiang
2014-10-31 19:39           ` Peter Feiner
2014-11-01  8:48             ` zhanghailiang
2014-11-20 17:29             ` Andrea Arcangeli
2014-11-12  7:18       ` zhanghailiang

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