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

[Avi Kivity]

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 
panic.