[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] memory performance 20% degradation in DomU -- Sisu
On Wed, Mar 05, 2014 at 09:29:30PM +0000, Gordan Bobic wrote: > Just out of interest, have you tried the same test with HVM DomU? > The two have different characteristics, and IIRC for some workloads > PV can be slower than HVM. The recent PVHVM work was intended to > result in the best aspects of both, but that is more recent than Xen > 4.3.0. > > It is also interesting that your findings are approximately similar > to mine, albeit with a very different testing methodology: > > http://goo.gl/lIUk4y Don't know if you used PV drivers (for HVM) and if you used as a backend a block device instead of a file. But it also helps in using 'fio' to test this sort of thing. > > Gordan > > On 03/05/2014 08:09 PM, Sisu Xi wrote: > >Hi, Konrad: > > > >It is the PV domU. > > > >Thanks. > > > >Sisu > > > > > >On Wed, Mar 5, 2014 at 11:33 AM, Konrad Rzeszutek Wilk > ><konrad.wilk@xxxxxxxxxx <mailto: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 > > <mailto: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 <mailto: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 > > > > > >_______________________________________________ > >Xen-devel mailing list > >Xen-devel@xxxxxxxxxxxxx > >http://lists.xen.org/xen-devel > > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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