On 06/15/2010 04:55 PM, Dave Hansen wrote:
In a previous patch, we removed the 'nr_to_scan' tracking. It was not being used to track the number of objects scanned, so we stopped using it entirely. Here, we strart using it again. The theory here is simple; if we already have the refcount and the kvm->mmu_lock, then we should do as much work as possible under the lock. The downside is that we're less fair about the KVM instances from which we reclaim. Each call to mmu_shrink() will tend to "pick on" one instance, after which it gets moved to the end of the list and left alone for a while.
That also increases the latency hit, as well as a potential fault storm, on that instance. Spreading out is less efficient, but smoother.
If mmu_shrink() has already done a significant amount of scanning, the use of 'nr_to_scan' inside shrink_kvm_mmu() will also ensure that we do not over-reclaim when we have already done a lot of work in this call. In the end, this patch defines a "scan" as: 1. An attempt to acquire a refcount on a 'struct kvm' 2. freeing a kvm mmu page This would probably be most ideal if we can expose some of the work done by kvm_mmu_remove_some_alloc_mmu_pages() as also counting as scanning, but I think we have churned enough for the moment.
It usually removes one page.
Signed-off-by: Dave Hansen<dave@xxxxxxxxxxxxxxxxxx> --- linux-2.6.git-dave/arch/x86/kvm/mmu.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff -puN arch/x86/kvm/mmu.c~make-shrinker-more-aggressive arch/x86/kvm/mmu.c --- linux-2.6.git/arch/x86/kvm/mmu.c~make-shrinker-more-aggressive 2010-06-14 11:30:44.000000000 -0700 +++ linux-2.6.git-dave/arch/x86/kvm/mmu.c 2010-06-14 11:38:04.000000000 -0700 @@ -2935,8 +2935,10 @@ static int shrink_kvm_mmu(struct kvm *kv idx = srcu_read_lock(&kvm->srcu); spin_lock(&kvm->mmu_lock); - if (kvm->arch.n_used_mmu_pages> 0) - freed_pages = kvm_mmu_remove_some_alloc_mmu_pages(kvm); + while (nr_to_scan> 0&& kvm->arch.n_used_mmu_pages> 0) { + freed_pages += kvm_mmu_remove_some_alloc_mmu_pages(kvm); + nr_to_scan--; + }
What tree are you patching? -- 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