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kvm: ppc: stop leaking host memory on VM exit

PATCH In review Hollis Blanchard 5 participants 5 messages Nov 24, 2008 – Nov 25, 2008 2 messages not in the archive

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Hollis Blanchard

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#0 lore raw

PATCH 1/1 kvm: ppc: stop leaking host memory on VM exit

When the VM exits, we must call put_page() for every page referenced in the shadow TLB.

Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB pages). The maximum number of pages leaked is the size of our shadow TLB, 64 pages.

Signed-off-by Hollis Blanchard <[email protected]>

---
The obvious question is "why didn't we see this before?" Basically, we'd never looked for it, and since most of our work was in the kernel we always ended up rebooting before exhausting host memory.

Since it's such a large leak, and a simple fix, please commit this for 2.6.28. This patch does apply to kvm.git with fuzz, but if you prefer I can send a separate patch for that later.

arch/powerpc/include/asm/kvm_ppc.h +2 -0
@@ -104,4 +104,6 @@ static inline void kvmppc_set_pid(struct
 	}
 }
 
+extern void kvmppc_core_destroy_mmu(struct kvm_vcpu *vcpu);
+
 #endif /* __POWERPC_KVM_PPC_H__ */
arch/powerpc/kvm/44x_tlb.c +8 -0
@@ -124,6 +124,14 @@ static void kvmppc_44x_shadow_release(st
 	}
 }
 
+void kvmppc_core_destroy_mmu(struct kvm_vcpu *vcpu)
+{
+	int i;
+
+	for (i = 0; i <= tlb_44x_hwater; i++)
+		kvmppc_44x_shadow_release(vcpu, i);
+}
+
 void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i)
 {
     vcpu->arch.shadow_tlb_mod[i] = 1;
arch/powerpc/kvm/powerpc.c +1 -0
@@ -238,6 +238,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *
 
 void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
 {
+	kvmppc_core_destroy_mmu(vcpu);
 }
 
 /* Note: clearing MSR[DE] just means that the debug interrupt will not be
Signature · 2 lines
Hollis Blanchard
IBM Linux Technology Center

A message that is not in the archive (sent off-list or not yet received): 1227548258.17746.11.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/[email protected]

#2 lore raw

Good catch.

Quoted 26 lines

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Hollis Blanchard
Sent: Tuesday, November 25, 2008 1:38 AM
To: Avi Kivity
Cc: kvm-ppc; kvm
Subject: [PATCH] kvm: ppc: stop leaking host memory on VM exit

When the VM exits, we must call put_page() for every page referenced in the
shadow TLB.

Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB
pages). The maximum number of pages leaked is the size of our shadow TLB, 64
pages.

Signed-off-by Hollis Blanchard <hollisb-r/[email protected]>

---
The obvious question is "why didn't we see this before?" Basically, we'd never
looked for it, and since most of our work was in the kernel we always ended up
rebooting before exhausting host memory.

Quoted 6 lines

Since it's such a large leak, and a simple fix, please commit this for 2.6.28.
This patch does apply to kvm.git with fuzz, but if you prefer I can send a
separate patch for that later.

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#3 lore raw
In reply to Hollis Blanchard
Quoted 12 lines

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Hollis Blanchard
Sent: Tuesday, November 25, 2008 1:38 AM
To: Avi Kivity
Cc: kvm-ppc; kvm
Subject: [PATCH] kvm: ppc: stop leaking host memory on VM exit

When the VM exits, we must call put_page() for every page referenced in the
shadow TLB.

Quoted 7 lines

Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB
pages). The maximum number of pages leaked is the size of our shadow TLB, 64
pages.

Signed-off-by Hollis Blanchard <[email protected]>

Need it also to _tlbia() at vcpu_uninit?

A message that is not in the archive (sent off-list or not yet received): D8176E55B81822498D63816C4ADC701023423D-bKEhWGtIRUJ4Lp7cDGe+DVjVikpgYyvb5NbjCUgZEJk@public.gmane.org

#5 lore raw
Quoted 18 lines · Liu Yu
Quoted 18 lines

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Hollis Blanchard
Sent: Tuesday, November 25, 2008 1:38 AM
To: Avi Kivity
Cc: kvm-ppc; kvm
Subject: [PATCH] kvm: ppc: stop leaking host memory on VM exit

When the VM exits, we must call put_page() for every page referenced in the
shadow TLB.

Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB
pages). The maximum number of pages leaked is the size of our shadow TLB, 64
pages.

Quoted 3 lines
Quoted 1 line
Signed-off-by Hollis Blanchard <hollisb-r/[email protected]>

Need it also to _tlbia() at vcpu_uninit?

No, because by the time we hit kvm_arch_vcpu_uninit(), kvm_arch_vcpu_put() has already been called.

Signature · 7 lines
Hollis Blanchard
IBM Linux Technology Center

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More majordomo info at  http://vger.kernel.org/majordomo-info.html
#6 lore raw
In reply to Hollis Blanchard
Quoted 8 lines · Hollis Blanchard

When the VM exits, we must call put_page() for every page referenced in the shadow TLB.

Without this patch, we usually leak 30-50 host pages (120 - 200 KiB with 4 KiB pages). The maximum number of pages leaked is the size of our shadow TLB, 64 pages.

Signed-off-by Hollis Blanchard <[email protected]>
Quoted 9 lines

---
The obvious question is "why didn't we see this before?" Basically, we'd never looked for it, and since most of our work was in the kernel we always ended up rebooting before exhausting host memory.

Since it's such a large leak, and a simple fix, please commit this for 2.6.28. This patch does apply to kvm.git with fuzz, but if you prefer I can send a separate patch for that later.

Applied on both master and the 2.6.28 queue.

Signature · 1 line
error compiling committee.c: too many arguments to function