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[Qemu-devel] Re: [RFC] KVM Fault Tolerance: Kemari for KVM

From: Avi Kivity
Subject: [Qemu-devel] Re: [RFC] KVM Fault Tolerance: Kemari for KVM
Date: Wed, 18 Nov 2009 15:58:32 +0200
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On 11/18/2009 03:28 PM, Yoshiaki Tamura wrote:

I don't think lmbench is intensive but it's sensitive to memory latency.
We'll measure kernel build time with minimum config, and post it later.
Here are some quick numbers of parallel kernel compile time.
The number of vcpu is 1, just for convenience.

time make -j 2 all
Base:    real 1m13.950s (user 1m2.742s, sys 0m10.446s)
Kemari: real 1m22.720s (user 1m5.882s, sys 0m10.882s)

time make -j 4 all
Base:    real 1m11.234s (user 1m2.582s, sys 0m8.643s)
Kemari: real 1m26.964s (user 1m6.530s, sys 0m12.194s)

The result of Kemari includes everything, meaning dirty pages tracking and
synchronization upon I/O operations to the disk.
The compile time using j=4 under Kemari was worse than that of j=2,
but I'm not sure this is due to dirty pages tracking or sync interval.

Do disk writes trigger synchronization? Otherwise this is a very relaxed test. I'm surprised the degradation is so low running continuously in log-dirty.

Is this an npt or ept system? Without npt or ept I'd expect less degradation since the page tables are heavily manipulated anyway.

Do not meddle in the internals of kernels, for they are subtle and quick to 

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