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Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm

From: Avi Kivity
Subject: Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm
Date: Tue, 25 May 2010 19:27:23 +0300
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4

On 05/25/2010 07:21 PM, Anthony Liguori wrote:
On 05/25/2010 11:16 AM, Avi Kivity wrote:
On 05/25/2010 06:01 PM, Anthony Liguori wrote:
On 05/25/2010 10:00 AM, Avi Kivity wrote:
The latter. Why is it less important? If you don't inherit the memory, you can't access it.

You can also pass /dev/shm fd's via SCM_RIGHTs to establish shared memory segments dynamically.

Doesn't work for anonymous memory.

What's wrong with /dev/shm memory?

The kernel treats anonymous and nonymous memory differently for swapping (see /proc/sys/vm/swappiness); transparent hugepages won't work for /dev/shm (though it may be argued that that's a problem with thp); setup (/dev/shm defaults to half memory IIRC, we want mem+swap); different cgroup handling; somewhat clunky (a minor concern to be sure).

Surely, with mmu notifiers, it wouldn't be that hard to share anonymous memory via an fd though, no?

That's what I suggested with processfd(). I wouldn't call it easy but it's likely doable. Whether it's mergable is a different issue.

error compiling committee.c: too many arguments to function

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