On 05/10/2012 05:33 PM, Takuya Yoshikawa wrote:
> From: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
>
> lpage_info is created for each large level even when the memory slot is
> not for RAM. This means that when we add one slot for a PCI device, we
> end up allocating at least KVM_NR_PAGE_SIZES - 1 pages by vmalloc():
> this problem will become severer if we support more guests with more
> devices in the future.
>
> Although it is not easy to differentiate RAM slots from others, we can
> avoid wasting pages by making KVM_NR_PAGE_SIZES - 1 lpage_info arrays
> coalesce into one and using kmalloc() when the result is small enough.
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 56 ++++++++++++++++++++++++++++++---------------------
> 1 files changed, 33 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4de705c..716d543 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6300,35 +6300,52 @@ void kvm_arch_free_memslot(struct kvm_memory_slot *free,
> {
> int i;
>
> - for (i = 0; i < KVM_NR_PAGE_SIZES - 1; ++i) {
> - if (!dont || free->arch.lpage_info[i] != dont->arch.lpage_info[i]) {
> - vfree(free->arch.lpage_info[i]);
> - free->arch.lpage_info[i] = NULL;
> - }
> - }
> + if (dont && free->arch.lpage_info[0] == dont->arch.lpage_info[0])
> + return;
> +
> + if (is_vmalloc_addr(free->arch.lpage_info[0]))
> + vfree(free->arch.lpage_info[0]);
> + else
> + kfree(free->arch.lpage_info[0]);
> +
> + for (i = 0; i < KVM_NR_PAGE_SIZES - 1; ++i)
> + free->arch.lpage_info[i] = NULL;
> }
>
I don't feel that the savings is worth the extra complication. We save
two pages per memslot here.
What about using kvmalloc() instead of vmalloc()? It's in
security/apparmor now, but can be made generic.
--
error compiling committee.c: too many arguments to function
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
