From: Avi Kivity <avi@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Haggai Eran <haggaie@mellanox.com>,
linux-mm@kvack.org, Andrea Arcangeli <aarcange@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
Shachar Raindel <raindel@mellanox.com>,
Sagi Grimberg <sagig@mellanox.com>,
Or Gerlitz <ogerlitz@mellanox.com>
Subject: Re: [PATCH V1 0/2] Enable clients to schedule in mmu_notifier methods
Date: Wed, 05 Sep 2012 15:55:23 +0300 [thread overview]
Message-ID: <50474BBB.2070509@redhat.com> (raw)
In-Reply-To: <20120904150615.f6c1a618.akpm@linux-foundation.org>
On 09/05/2012 01:06 AM, Andrew Morton wrote:
> On Tue, 4 Sep 2012 11:41:19 +0300
> Haggai Eran <haggaie@mellanox.com> wrote:
>
>> > This patchset is a preliminary step towards on-demand paging design to be
>> > added to the Infiniband stack.
>
> The above sentence is the most important part of the patchset. Because
> it answers the question "ytf is Haggai sending this stuff at me".
>
> I'm unsure if the patchset adds runtime overhead but it does add
> maintenance overhead (perhaps we can reduce this - see later emails).
> So we need to take a close look at what we're getting in return for
> that overhead, please.
>
> Exactly why do we want on-demand paging for Infiniband? Why should
> anyone care? What problems are users currently experiencing? How many
> users and how serious are the problems and what if any workarounds are
> available?
>
> Is there any prospect that any other subsystems will utilise these
> infrastructural changes? If so, which and how, etc?
>
>
>
> IOW, sell this code to us!
kvm may be a buyer. kvm::mmu_lock, which serializes guest page faults,
also protects long operations such as destroying large ranges. It would
be good to convert it into a spinlock, but as it is used inside mmu
notifiers, this cannot be done.
(there are alternatives, such as keeping the spinlock and using a
generation counter to do the teardown in O(1), which is what the "may"
is doing up there).
--
error compiling committee.c: too many arguments to function
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next prev parent reply other threads:[~2012-09-05 12:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-04 8:41 [PATCH V1 0/2] Enable clients to schedule in mmu_notifier methods Haggai Eran
2012-09-04 8:41 ` [PATCH V1 1/2] mm: Move all mmu notifier invocations to be done outside the PT lock Haggai Eran
2012-09-04 22:07 ` Andrew Morton
2012-09-06 14:34 ` [PATCH V2 0/2] Enable clients to schedule in mmu_notifier methods Haggai Eran
2012-09-06 14:34 ` [PATCH V2 1/2] mm: Move all mmu notifier invocations to be done outside the PT lock Haggai Eran
2012-09-06 14:34 ` [PATCH V2 2/2] mm: Wrap calls to set_pte_at_notify with invalidate_range_start and invalidate_range_end Haggai Eran
2012-09-06 20:08 ` [PATCH V2 0/2] Enable clients to schedule in mmu_notifier methods Andrew Morton
2012-09-04 8:41 ` [PATCH V1 2/2] mm: Wrap calls to set_pte_at_notify with invalidate_range_start and invalidate_range_end Haggai Eran
2012-09-04 22:07 ` Andrew Morton
2012-09-04 22:06 ` [PATCH V1 0/2] Enable clients to schedule in mmu_notifier methods Andrew Morton
2012-09-05 12:55 ` Avi Kivity [this message]
2012-09-05 14:01 ` Haggai Eran
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