Re: [Xen-devel] memory performance 20% degradation in DomU -- Sisu

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Mar 05, 2014 at 02:09:20PM -0600, Sisu Xi wrote:
> Hi, Konrad:
> 
> It is the PV domU.

Please try PVHVM as well.

And please don't top post.
> 
> Thanks.
> 
> Sisu
> 
> 
> On Wed, Mar 5, 2014 at 11:33 AM, Konrad Rzeszutek Wilk <
> konrad.wilk@xxxxxxxxxx> wrote:
> 
> > On Tue, Mar 04, 2014 at 05:00:46PM -0600, Sisu Xi wrote:
> > > Hi, all:
> > >
> > > I also used the ramspeed to measure memory throughput.
> > > http://alasir.com/software/ramspeed/
> > >
> > > I am using the v2.6, single core version. The command I used is
> > ./ramspeed
> > > -b 3 (for int) and ./ramspeed -b 6 (for float).
> > > The benchmark measures four operations: add, copy, scale, and triad. And
> > > also gives an average number for all four operations.
> > >
> > > The results in DomU shows around 20% performance degradation compared to
> > > non-virt results.
> >
> > What kind of domU? PV or HVM?
> > >
> > > Attached is the results. The left part are results for int, while the
> > right
> > > part is the results for float. The Y axis is the measured throughput.
> > Each
> > > box contains 100 experiment repeats.
> > > The black boxes are the results in non-virtualized environment, while the
> > > blue ones are the results I got in DomU.
> > >
> > > The Xen version I am using is 4.3.0, 64bit.
> > >
> > > Thanks very much!
> > >
> > > Sisu
> > >
> > >
> > >
> > > On Tue, Mar 4, 2014 at 4:49 PM, Sisu Xi <xisisu@xxxxxxxxx> wrote:
> > >
> > > > Hi, all:
> > > >
> > > > I am trying to study the cache/memory performance under Xen, and has
> > > > encountered some problems.
> > > >
> > > > My machine is has an Intel Core i7 X980 processor with 6 physical
> > cores. I
> > > > disabled hyper-threading, frequency scaling, so it should be running at
> > > > constant speed.
> > > > Dom0 was boot with 1 VCPU pinned to 1 core, with 2 GB of memory.
> > > >
> > > > After that, I boot up DomU with 1 VCPU pinned to a separate core, with
> > 1
> > > > GB of memory. The credit scheduler is used, and no cap is set for
> > them. So
> > > > DomU should be able to access all resources.
> > > >
> > > > Each physical core has a 32KB dedicated L1 cache, 256KB dedicated L2
> > > > cache. And all cores share a 12MB L3 cache.
> > > >
> > > > I created a simple program to create an array of specified size. Load
> > them
> > > > once, and then randomly access every cache line once. (1 cache line is
> > 64B
> > > > on my machine).
> > > > rdtsc is used to record the duration for the random access.
> > > >
> > > > I tried different data sizes, with 1000 repeat for each data sizes.
> > > > Attached is the boxplot for average access time for one cache line.
> > > >
> > > > The x axis is the different Data Size, the y axis is the CPU cycle. The
> > > > three vertical lines at 32KB, 256KB, and 12MB represents the size
> > > > difference in L1, L2, and L3 cache on my machine.
> > > > *The black box are the results I got when I run it in non-virtualized,
> > > > while the blue box are the results I got in DomU.*
> > > >
> > > > For some reason, the results in DomU varies much more than the results
> > in
> > > > non-virtualized environment.
> > > > I also repeated the same experiments in DomU with Run Level 1, the
> > results
> > > > are the same.
> > > >
> > > > Can anyone give some suggestions about what might be the reason for
> > this?
> > > >
> > > > Thanks very much!
> > > >
> > > > Sisu
> > > >
> > > > --
> > > > Sisu Xi, PhD Candidate
> > > >
> > > > http://www.cse.wustl.edu/~xis/
> > > > Department of Computer Science and Engineering
> > > > Campus Box 1045
> > > > Washington University in St. Louis
> > > > One Brookings Drive
> > > > St. Louis, MO 63130
> > > >
> > >
> > >
> > >
> > > --
> > > Sisu Xi, PhD Candidate
> > >
> > > http://www.cse.wustl.edu/~xis/
> > > Department of Computer Science and Engineering
> > > Campus Box 1045
> > > Washington University in St. Louis
> > > One Brookings Drive
> > > St. Louis, MO 63130
> >
> >
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxx
> > > http://lists.xen.org/xen-devel
> >
> >
> 
> 
> -- 
> Sisu Xi, PhD Candidate
> 
> http://www.cse.wustl.edu/~xis/
> Department of Computer Science and Engineering
> Campus Box 1045
> Washington University in St. Louis
> One Brookings Drive
> St. Louis, MO 63130

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