Re: kvm userspace: ksm support

[Izik Eidus]

Brian Jackson wrote:

On Monday 03 August 2009 01:09:38 pm Izik Eidus wrote:

Brian Jackson wrote:

If someone wanted to play around with ksm in qemu-kvm-0.x.x would it be
as simple as adding the below additions to kvm_setup_guest_memory in
kvm-all.c

qemu-kvm-0.x.x doesnt tell me much, but if it is the function that
register the memory than yes...

(I just remember that qemu used to have something called phys_ram_base,
in that case it would be just making madvise on phys_ram_base with the
same of phys_ram_size....)

Sorry, I'm using qemu-kvm-0.10.6


This is what qemu_ram_alloc looks like:



/* XXX: better than nothing */
ram_addr_t qemu_ram_alloc(ram_addr_t size)
{
    ram_addr_t addr;
    if ((phys_ram_alloc_offset + size) > phys_ram_size) {
        fprintf(stderr, "Not enough memory (requested_size = %" PRIu64 ", max memory = %" 
PRIu64 ")\n",
                (uint64_t)size, (uint64_t)phys_ram_size);
        abort();
    }
    addr = phys_ram_alloc_offset;
    phys_ram_alloc_offset = TARGET_PAGE_ALIGN(phys_ram_alloc_offset + size);

    if (kvm_enabled())
        kvm_setup_guest_memory(phys_ram_base + addr, size);

    return addr;
}


And this is what my new kvm_setup_guest_memory looks like:


void kvm_setup_guest_memory(void *start, size_t size)
{
    if (!kvm_has_sync_mmu()) {
#ifdef MADV_DONTFORK
        int ret = madvise(start, size, MADV_DONTFORK);

        if (ret) {
            perror("madvice");
            exit(1);
        }
#else
        fprintf(stderr,
                "Need MADV_DONTFORK in absence of synchronous KVM MMU\n");
        exit(1);
#endif
    }
#ifdef MADV_MERGEABLE
        madvise(start, size, MADV_MERGEABLE);
#endif
}



Look okay?

Yes.
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