On Thu, Jul 05, 2012 at 07:56:07PM +0900, Takuya Yoshikawa wrote:
> The following commit changed mmu_shrink() so that it would skip VMs
> whose n_used_mmu_pages is not zero and try to free pages from others:
>
Oops,
> commit 1952639665e92481c34c34c3e2a71bf3e66ba362
> KVM: MMU: do not iterate over all VMs in mmu_shrink()
>
> This patch fixes the function so that it can free mmu pages as before.
>
> Note that "if (!nr_to_scan--)" check is removed since we do not try to
> free mmu pages from more than one VM.
>
IIRC this was proposed in the past that we should iterate over vm list
until freeing something eventually, but Avi was against it. I think the
probability of a VM with kvm->arch.n_used_mmu_pages == 0 is low, so
it looks OK to drop nr_to_scan to me.
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 5 +----
> 1 files changed, 1 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 3b53d9e..5fd268a 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3957,11 +3957,8 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
> * want to shrink a VM that only started to populate its MMU
> * anyway.
> */
> - if (kvm->arch.n_used_mmu_pages > 0) {
> - if (!nr_to_scan--)
> - break;
> + if (!kvm->arch.n_used_mmu_pages)
> continue;
> - }
>
> idx = srcu_read_lock(&kvm->srcu);
> spin_lock(&kvm->mmu_lock);
> --
> 1.7.5.4
--
Gleb.
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