Messages in this thread | | | Date | Thu, 17 Jun 2010 11:37:20 +0300 | From | Avi Kivity <> | Subject | Re: [RFC][PATCH 9/9] make kvm mmu shrinker more aggressive |
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On 06/16/2010 06:25 PM, Dave Hansen wrote: > >>> 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. >> > Does it always just go right now and free it, or is there any real > scanning that has to go on? >
It picks a page from the tail of the LRU and frees it. There is very little attempt to keep the LRU in LRU order, though.
We do need a scanner that looks at spte accessed bits if this isn't going to result in performance losses.
>>> 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? >> > These applied to Linus's latest as of yesterday. >
Please patch against kvm.git master (or next, which is usually a few unregression-tested patches ahead). This code has changed.
-- error compiling committee.c: too many arguments to function
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