On 09/05/2012 01:06 AM, Andrew Morton wrote:

On Tue,  4 Sep 2012 11:41:19 +0300
Haggai Eran [off-list ref] wrote:

quoted

quoted

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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