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xen-devel
[Xen-devel] Re: [RFC PATCH 0/4] (Take 2): transcendent memory ("tmem") f
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To: |
Avi Kivity <avi@xxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [RFC PATCH 0/4] (Take 2): transcendent memory ("tmem") for Linux |
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From: |
Anthony Liguori <anthony@xxxxxxxxxxxxx> |
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Date: |
Sun, 12 Jul 2009 14:34:25 -0500 |
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Cc: |
npiggin@xxxxxxx, akpm@xxxxxxxx, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, tmem-devel@xxxxxxxxxxxxxx, kurt.hackel@xxxxxxxxxx, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, sunil.mushran@xxxxxxxxxx, chris.mason@xxxxxxxxxx, jeremy@xxxxxxxx, Schwidefsky <schwidefsky@xxxxxxxxxx>, dave.mccracken@xxxxxxxxxx, Marcelo Tosatti <mtosatti@xxxxxxxxxx>, alan@xxxxxxxxxxxxxxxxxxx, Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> |
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Sun, 12 Jul 2009 12:34:54 -0700 |
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Avi Kivity wrote:
In fact CMM2 is much more intrusive (but on the other hand provides
much more information).
I don't think this will remain true long term. CMM2 touches a lot of
core mm code and certainly qualifies as intrusive. However the result
is that the VMM has a tremendous amount of insight into how the guest is
using it's memory and can implement all sorts of fancy policy for
reclaim. Since the reclaim policy can evolve without any additional
assistance from the guest, the guest doesn't have to change as policy
evolves.
Since tmem requires that reclaim policy is implemented within the guest,
I think in the long term, tmem will have to touch a broad number of
places within Linux. Beside the core mm, the first round of patches
already touch filesystems (just ext3 to start out with). To truly be
effective, tmem would have to be a first class kernel citizen and I
suspect a lot of code would have to be aware of it.
So while CMM2 does a lot of code no one wants to touch, I think in the
long term it would remain relatively well contained compared to tmem
which will steadily increase in complexity within the guest.
Regards,
Anthony Liguori
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