KVM: register the kvm mmu cache with the shrinker.

[Izik Eidus <izike@qumranet.com>]

this is the shrinker patch with all comments applied beside adding aging mechanism
it look like the aging mechanism is not really needed and therefor for now it isn't
implemented.

>From 8503a57ae88ba819e4eac6371172772c98b485f0 Mon Sep 17 00:00:00 2001
From: Izik Eidus <izike@qumranet.com>
Date: Tue, 25 Mar 2008 14:03:27 +0200
Subject: [PATCH] KVM: register the kvm mmu cache with the shrinker.

Signed-off-by: Izik Eidus <izike@qumranet.com>
---
 arch/x86/kvm/mmu.c |   54 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 54 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index c67ec62..c42c0db 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1972,6 +1972,57 @@ void kvm_mmu_zap_all(struct kvm *kvm)
 	kvm_flush_remote_tlbs(kvm);
 }
 
+void kvm_mmu_remove_one_alloc_mmu_page(struct kvm *kvm)
+{
+	struct kvm_mmu_page *page;
+
+	page = container_of(kvm->arch.active_mmu_pages.prev,
+			    struct kvm_mmu_page, link);
+	kvm_mmu_zap_page(kvm, page);
+}
+
+static int mmu_shrink(int nr_to_scan, gfp_t gfp_mask)
+{
+	struct kvm *kvm;
+	struct kvm *kvm_freed = NULL;
+	int cache_count = 0;
+
+	spin_lock(&kvm_lock);
+	if (list_empty(&vm_list)) {
+		spin_unlock(&kvm_lock);
+		return 0;
+	}
+	list_for_each_entry(kvm, &vm_list, vm_list) {
+		int npages;
+
+		spin_lock(&kvm->mmu_lock);
+		npages = kvm->arch.n_alloc_mmu_pages -
+			 kvm->arch.n_free_mmu_pages;
+		cache_count += npages - KVM_MIN_ALLOC_MMU_PAGES;
+		if (!kvm_freed && nr_to_scan > 0 && npages >
+		    KVM_MIN_ALLOC_MMU_PAGES) {
+			kvm_mmu_remove_one_alloc_mmu_page(kvm);
+			cache_count--;
+			kvm_freed = kvm;
+		}
+		nr_to_scan--;
+
+		spin_unlock(&kvm->mmu_lock);
+	}
+	if (kvm_freed) {
+		list_del(&kvm_freed->vm_list);
+		list_add_tail(&kvm_freed->vm_list, &vm_list);
+	}
+	spin_unlock(&kvm_lock);
+
+	return cache_count;
+}
+
+static struct shrinker mmu_shrinker = {
+	.shrink = mmu_shrink,
+	.seeks = DEFAULT_SEEKS * 10,
+};
+
 void kvm_mmu_module_exit(void)
 {
 	if (pte_chain_cache)
@@ -1980,6 +2031,7 @@ void kvm_mmu_module_exit(void)
 		kmem_cache_destroy(rmap_desc_cache);
 	if (mmu_page_header_cache)
 		kmem_cache_destroy(mmu_page_header_cache);

-- 
woof.

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