On Sat, Jan 22, 2022 at 5:00 PM Barry Smith <bsm...@petsc.dev> wrote:
> > The GPU flop rate (when 100 percent flops on the GPU) should always be > higher than the overall flop rate (the previous column). For large problems > they should be similar, for small problems the GPU one may be much higher. > > If the CPU one is higher (when 100 percent flops on the GPU) something > must be wrong with the logging. I looked at the code for the two cases and > didn't see anything obvious. > > Junchao and Jacob, > I think some of the timing code in the Kokkos interface is wrong. > > * The PetscLogGpuTimeBegin/End should be inside the viewer access > code not outside it. (The GPU time is an attempt to best time the kernels, > not other processing around the use of the kernels, that other stuff is > captured in the general LogEventBegin/End. > Good point > * The use of WaitForKokkos() is confusing and seems inconsistent. > I need to have a look. Until now, I have not paid much attention to kokkos profiling. > -For example it is used in VecTDot_SeqKokkos() which I would > think has a barrier anyways because it puts a scalar result into update? > -Plus PetscLogGpuTimeBegin/End is suppose to already have > suitable system (that Hong added) to ensure the kernel is complete; reading > the manual page and looking at Jacobs cupmcontext.hpp it seems to be there > so I don't think WaitForKokkos() is needed in most places (or is Kokkos > asynchronous and needs this for correctness?) > But these won't explain the strange result of overall flop rate being > higher than GPU flop rate. > > Barry > > > > > > On Jan 22, 2022, at 11:44 AM, Mark Adams <mfad...@lbl.gov> wrote: > > I am getting some funny timings and I'm trying to figure it out. > I figure the gPU flop rates are bit higher because the timers are inside > of the CPU timers, but *some are a lot bigger or inverted* > > --- Event Stage 2: KSP Solve only > > MatMult 400 1.0 1.0094e+01 1.2 1.07e+11 1.0 3.7e+05 6.1e+04 > 0.0e+00 2 55 62 54 0 68 91100100 0 671849 857147 0 0.00e+00 0 > 0.00e+00 100 > MatView 2 1.0 4.5257e-03 2.5 0.00e+00 0.0 0.0e+00 0.0e+00 > 2.0e+00 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > KSPSolve 2 1.0 1.4591e+01 1.1 1.18e+11 1.0 3.7e+05 6.1e+04 > 1.2e+03 2 60 62 54 60 100100100100100 512399 804048 0 0.00e+00 0 > 0.00e+00 100 > SFPack 400 1.0 2.4545e-03 1.4 0.00e+00 0.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > SFUnpack 400 1.0 9.4637e-05 1.7 0.00e+00 0.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > VecTDot 802 1.0 3.0577e+00 2.1 3.36e+09 1.0 0.0e+00 0.0e+00 > 8.0e+02 0 2 0 0 40 13 3 0 0 67 *69996 488328* 0 0.00e+00 > 0 0.00e+00 100 > VecNorm 402 1.0 1.9597e+00 3.4 1.69e+09 1.0 0.0e+00 0.0e+00 > 4.0e+02 0 1 0 0 20 6 1 0 0 33 54744 571507 0 0.00e+00 0 > 0.00e+00 100 > VecCopy 4 1.0 1.7143e-0228.6 0.00e+00 0.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > VecSet 4 1.0 3.8051e-0316.9 0.00e+00 0.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > VecAXPY 800 1.0 8.6160e-0113.6 3.36e+09 1.0 0.0e+00 0.0e+00 > 0.0e+00 0 2 0 0 0 6 3 0 0 0 *247787 448304* 0 0.00e+00 > 0 0.00e+00 100 > VecAYPX 398 1.0 1.6831e+0031.1 1.67e+09 1.0 0.0e+00 0.0e+00 > 0.0e+00 0 1 0 0 0 5 1 0 0 0 63107 77030 0 0.00e+00 0 > 0.00e+00 100 > VecPointwiseMult 402 1.0 3.8729e-01 9.3 8.43e+08 1.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 2 1 0 0 0 138502 262413 0 0.00e+00 0 > 0.00e+00 100 > VecScatterBegin 400 1.0 1.1947e+0035.1 0.00e+00 0.0 3.7e+05 6.1e+04 > 0.0e+00 0 0 62 54 0 5 0100100 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > VecScatterEnd 400 1.0 6.2969e+00 8.8 0.00e+00 0.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 10 0 0 0 0 0 0 0 0.00e+00 0 > 0.00e+00 0 > PCApply 402 1.0 3.8758e-01 9.3 8.43e+08 1.0 0.0e+00 0.0e+00 > 0.0e+00 0 0 0 0 0 2 1 0 0 0 138396 262413 0 0.00e+00 0 > 0.00e+00 100 > > --------------------------------------------------------------------------------------------------------------------------------------------------------------- > > > On Sat, Jan 22, 2022 at 11:10 AM Junchao Zhang <junchao.zh...@gmail.com> > wrote: > >> >> >> >> On Sat, Jan 22, 2022 at 10:04 AM Mark Adams <mfad...@lbl.gov> wrote: >> >>> Logging GPU flops should be inside of PetscLogGpuTimeBegin()/End() >>> right? >>> >> No, PetscLogGpuTime() does not know the flops of the caller. >> >> >>> >>> On Fri, Jan 21, 2022 at 9:47 PM Barry Smith <bsm...@petsc.dev> wrote: >>> >>>> >>>> Mark, >>>> >>>> Fix the logging before you run more. It will help with seeing the >>>> true disparity between the MatMult and the vector ops. >>>> >>>> >>>> On Jan 21, 2022, at 9:37 PM, Mark Adams <mfad...@lbl.gov> wrote: >>>> >>>> Here is one with 2M / GPU. Getting better. >>>> >>>> On Fri, Jan 21, 2022 at 9:17 PM Barry Smith <bsm...@petsc.dev> wrote: >>>> >>>>> >>>>> Matt is correct, vectors are way too small. >>>>> >>>>> BTW: Now would be a good time to run some of the Report I >>>>> benchmarks on Crusher to get a feel for the kernel launch times and >>>>> performance on VecOps. >>>>> >>>>> Also Report 2. >>>>> >>>>> Barry >>>>> >>>>> >>>>> On Jan 21, 2022, at 7:58 PM, Matthew Knepley <knep...@gmail.com> >>>>> wrote: >>>>> >>>>> On Fri, Jan 21, 2022 at 6:41 PM Mark Adams <mfad...@lbl.gov> wrote: >>>>> >>>>>> I am looking at performance of a CG/Jacobi solve on a 3D Q2 Laplacian >>>>>> (ex13) on one Crusher node (8 GPUs on 4 GPU sockets, MI250X or is it >>>>>> MI200?). >>>>>> This is with a 16M equation problem. GPU-aware MPI and non GPU-aware >>>>>> MPI are similar (mat-vec is a little faster w/o, the total is about the >>>>>> same, call it noise) >>>>>> >>>>>> I found that MatMult was about 3x faster using 8 cores/GPU, that is >>>>>> all 64 cores on the node, then when using 1 core/GPU. With the same size >>>>>> problem of course. >>>>>> I was thinking MatMult should be faster with just one MPI process. Oh >>>>>> well, worry about that later. >>>>>> >>>>>> The bigger problem, and I have observed this to some extent with the >>>>>> Landau TS/SNES/GPU-solver on the V/A100s, is that the vector operations >>>>>> are >>>>>> expensive or crazy expensive. >>>>>> You can see (attached) and the times here that the solve is dominated >>>>>> by not-mat-vec: >>>>>> >>>>>> >>>>>> ------------------------------------------------------------------------------------------------------------------------ >>>>>> Event Count Time (sec) Flop >>>>>> --- Global --- --- Stage ---- *Total GPU * - >>>>>> CpuToGpu - - GpuToCpu - GPU >>>>>> Max Ratio Max Ratio Max Ratio Mess >>>>>> AvgLen Reduct %T %F %M %L %R %T %F %M %L %R *Mflop/s Mflop/s* >>>>>> Count Size Count Size %F >>>>>> >>>>>> --------------------------------------------------------------------------------------------------------------------------------------------------------------- >>>>>> 17:15 main= >>>>>> /gpfs/alpine/csc314/scratch/adams/petsc/src/snes/tests/data$ grep >>>>>> "MatMult >>>>>> 400" jac_out_00*5_8_gpuawaremp* >>>>>> MatMult 400 1.0 *1.2507e+00* 1.3 1.34e+10 1.1 3.7e+05 >>>>>> 1.6e+04 0.0e+00 1 55 62 54 0 27 91100100 0 *668874 0* >>>>>> 0 0.00e+00 0 0.00e+00 100 >>>>>> 17:15 main= >>>>>> /gpfs/alpine/csc314/scratch/adams/petsc/src/snes/tests/data$ grep >>>>>> "KSPSolve >>>>>> 2" jac_out_001*_5_8_gpuawaremp* >>>>>> KSPSolve 2 1.0 *4.4173e+00* 1.0 1.48e+10 1.1 3.7e+05 >>>>>> 1.6e+04 1.2e+03 4 60 62 54 61 100100100100100 *208923 1094405* >>>>>> 0 0.00e+00 0 0.00e+00 100 >>>>>> >>>>>> Notes about flop counters here, >>>>>> * that MatMult flops are not logged as GPU flops but something is >>>>>> logged nonetheless. >>>>>> * The GPU flop rate is 5x the total flop rate in KSPSolve :\ >>>>>> * I think these nodes have an FP64 peak flop rate of 200 Tflops, so >>>>>> we are at < 1%. >>>>>> >>>>> >>>>> This looks complicated, so just a single remark: >>>>> >>>>> My understanding of the benchmarking of vector ops led by Hannah was >>>>> that you needed to be much >>>>> bigger than 16M to hit peak. I need to get the tech report, but on 8 >>>>> GPUs I would think you would be >>>>> at 10% of peak or something right off the bat at these sizes. Barry, >>>>> is that right? >>>>> >>>>> Thanks, >>>>> >>>>> Matt >>>>> >>>>> >>>>>> Anway, not sure how to proceed but I thought I would share. >>>>>> Maybe ask the Kokkos guys if the have looked at Crusher. >>>>>> >>>>>> Mark >>>>>> >>>>> -- >>>>> What most experimenters take for granted before they begin their >>>>> experiments is infinitely more interesting than any results to which their >>>>> experiments lead. >>>>> -- Norbert Wiener >>>>> >>>>> https://www.cse.buffalo.edu/~knepley/ >>>>> <http://www.cse.buffalo.edu/~knepley/> >>>>> >>>>> >>>>> <jac_out_001_kokkos_Crusher_6_8_gpuawarempi.txt> >>>> >>>> >>>> <jac_out_001_kokkos_Crusher_5_8_notpl.txt> > <jac_out_001_kokkos_Crusher_6_8_notpl.txt> > > >
