RE: [Xen-ia64-devel] [PATCH] [Resend]Enable hash vtlb

[Alex Williamson <alex.williamson@xxxxxx>]

On Mon, 2006-04-10 at 22:07 +0800, Xu, Anthony wrote:
> Hi Alex,
> 
> Below data is got based on changeset 8489.
> 
> System:
>       Tiger 4
>       4G RAM (2GB available to xen)
>       Montecito 1.4GHz dual core dual thread.
>       DomU 512M RAM

   Adding memory might be interesting.  Perhaps there's a range of
memory where hash vtlb performs better.  For my dom0 testing, I booted
w/ dom0_mem=768M (as this seemed to be the most I could do).  For domU
testing, my xen config file specified 768MB of memory and dom0 was
booted w/ the standard 512MB.  This still left a difference of ~40MB as
reported by free once each domain is booted (domU has more memory).
Swap was disabled in both cases and all extraneous daemons were stopped.

> bare metal (UP):
> Total TimeBuild Time 2  Build Time 1
> =====================================================================
> 4008 Second  2004 Second  1995 Second
> =====================================================================
> 
> domU w/o hash vtlb
> Total TimeBuild Time 2  Build Time 1  
> =====================================================================
> 3966 Second  1976 Second  1978 Second  
> =====================================================================

   I don't understand this result.  I was surprised to see domU perform
better than dom0 in my testing, but I can't see how domU could perform
better than bare metal.  Perhaps 512MB is insufficient for kernel
builds.  You may be disproportionately benefiting from dom0's buffer
cache.

> domU w/ hash vtlb
> Total Time      Build Time1  Build Time2
> =====================================================================
> 3959 Second  1970 Second  1975 Second  
> =====================================================================
> 
> 
> DomU can still get better performance after applying hash_vtlb patch.
> This performance gain is based on 2% degradation of Dom0.(I don't get 
> performance
> data on Dom0 this time)
> 
> The attachment is the script which I used to get kernel build performance.
> Usage Example,
> ./make_kernel.sh    2    /root/linux-2.6.16.tar.bz2
>                   (times of build)   (absolute path)  

   The attachment seems to have been lost to a virus scanner.  My test
was simply:

# make clean
# time make > /dev/null 2>&1
repeat

Thanks,

        Alex

-- 
Alex Williamson                             HP Linux & Open Source Lab


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