hi there, I have this Go program that reads a binary file format coming from CERN. I am trying to get it running almost as fast as its C++ counter-part.
the profile and code are here: - https://cern.ch/binet/go-hep/rootio.cpu.pprof - https://cern.ch/binet/go-hep/read-data.go on my machine, I get the following timings for the C++ (g++-7.2.0) and the Go-1.9.1 programs: === C++/ROOT === real=6.84 user=6.29 sys=0.52 CPU=99% MaxRSS=258384 I/O=0/0 real=6.99 user=6.42 sys=0.55 CPU=99% MaxRSS=258312 I/O=0/0 real=6.68 user=6.12 sys=0.55 CPU=99% MaxRSS=257956 I/O=0/0 real=6.88 user=6.33 sys=0.54 CPU=99% MaxRSS=258964 I/O=0/0 real=6.87 user=6.30 sys=0.56 CPU=99% MaxRSS=258024 I/O=0/0 real=6.89 user=6.32 sys=0.56 CPU=99% MaxRSS=260452 I/O=0/0 real=6.70 user=6.14 sys=0.56 CPU=99% MaxRSS=258368 I/O=0/0 real=7.02 user=6.47 sys=0.54 CPU=99% MaxRSS=258128 I/O=0/0 real=7.46 user=6.44 sys=0.56 CPU=93% MaxRSS=257972 I/O=1840/0 real=7.11 user=6.47 sys=0.55 CPU=98% MaxRSS=258148 I/O=3984/0 === go-hep/rootio === real=13.06 user=12.43 sys=0.61 CPU=99% MaxRSS=40864 I/O=0/0 real=13.05 user=12.46 sys=0.58 CPU=100% MaxRSS=40892 I/O=0/0 real=13.05 user=12.46 sys=0.59 CPU=100% MaxRSS=40888 I/O=0/0 real=13.07 user=12.48 sys=0.58 CPU=99% MaxRSS=40940 I/O=0/0 real=13.08 user=12.48 sys=0.60 CPU=100% MaxRSS=40924 I/O=0/0 real=13.09 user=12.46 sys=0.60 CPU=99% MaxRSS=40976 I/O=0/0 real=13.01 user=12.41 sys=0.60 CPU=100% MaxRSS=40876 I/O=0/0 real=13.09 user=12.52 sys=0.58 CPU=100% MaxRSS=40880 I/O=0/0 real=13.01 user=12.41 sys=0.60 CPU=100% MaxRSS=40880 I/O=0/0 real=12.99 user=12.41 sys=0.58 CPU=100% MaxRSS=40872 I/O=0/0 any idea on how to speed that up? I have also this rather interesting strace-log for the Go program: - https://cern.ch/binet/go-hep/strace-read-go.txt ie: there is a clear pattern of "epoll_wait/pselect6" on one thread followed by a bunch of "pread64" on another thread. I suspect this is the runtime I/O layer (?) dispatching data to the "worker" thread/goroutine ? (I have tried with GOGC=off and it was still there, as well as the same timings for my Go binary.) I have put a ~764Mb data file there: - https://cern.ch/binet/go-hep/f64s.root if anybody wants to have a look. I initially thought it was a (lack of) bufio.Reader issue (as the file format forces you to do a bunch of seeks or readat, using bufio.Reader wasn't completely straightforward.) but, mmap-ing the whole file in memory didn't help. here is the top50 from the CPU profile: (pprof) top50 Showing nodes accounting for 12.90s, 99.15% of 13.01s total Dropped 4 nodes (cum <= 0.07s) flat flat% sum% cum cum% 2.83s 21.75% 21.75% 3.21s 24.67% go-hep.org/x/hep/rootio.(*LeafD).readBasket /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/leaf_gen.go 1.35s 10.38% 32.13% 12.99s 99.85% go-hep.org/x/hep/rootio.(*Scanner).Scan /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/scanner.go 1.26s 9.68% 41.81% 1.26s 9.68% go-hep.org/x/hep/rootio.(*tbranch).loadEntry /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/basket.go 1.17s 8.99% 50.81% 2.01s 15.45% go-hep.org/x/hep/rootio.(*tbranch).loadBasket /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/branch.go 1.15s 8.84% 59.65% 7.15s 54.96% go-hep.org/x/hep/rootio.(*tbranch).loadEntry /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/branch.go 0.82s 6.30% 65.95% 3.06s 23.52% go-hep.org/x/hep/rootio.(*tbranch).scan /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/branch.go 0.76s 5.84% 71.79% 3.90s 29.98% go-hep.org/x/hep/rootio.(*Basket).readLeaf /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/basket.go 0.62s 4.77% 76.56% 1.55s 11.91% go-hep.org/x/hep/rootio.(*LeafD).scan /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/leaf_gen.go 0.56s 4.30% 80.86% 0.56s 4.30% syscall.Syscall6 /usr/lib/go/src/syscall/asm_linux_amd64.s 0.44s 3.38% 84.24% 0.93s 7.15% reflect.Indirect /usr/lib/go/src/reflect/value.go 0.38s 2.92% 87.16% 0.38s 2.92% reflect.Value.Elem /usr/lib/go/src/reflect/value.go 0.34s 2.61% 89.78% 0.34s 2.61% reflect.ValueOf /usr/lib/go/src/reflect/value.go 0.28s 2.15% 91.93% 0.28s 2.15% go-hep.org/x/hep/rootio.(*tbranch).findBasketIndex /home/binet/dev/go/gocode/src/go-hep.org/x/hep/rootio/branch.go 0.21s 1.61% 93.54% 0.21s 1.61% go-hep.org/x/hep/rootio.(*LeafD).Len <autogenerated> 0.18s 1.38% 94.93% 0.18s 1.38% go-hep.org/x/hep/rootio.(*LeafD).UnmarshalROOT /home/binet/dev/go/gocode/src/go-hep.org/x/hep/rootio/rbuffer.go 0.17s 1.31% 96.23% 0.17s 1.31% go-hep.org/x/hep/rootio.(*tbranch).loadEntry /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/rbuffer.go 0.11s 0.85% 97.08% 0.11s 0.85% reflect.Value.Elem /usr/lib/go/src/reflect/type.go 0.09s 0.69% 97.77% 0.09s 0.69% go-hep.org/x/hep/rootio.(*Basket).readLeaf /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/rbuffer.go 0.09s 0.69% 98.46% 0.09s 0.69% go-hep.org/x/hep/rootio.(*LeafD).readBasket /usr/lib/go/src/encoding/binary/binary.go 0.08s 0.61% 99.08% 0.08s 0.61% go-hep.org/x/hep/rootio.(*tleaf).Offset /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/leaf.go 0.01s 0.077% 99.15% 13.01s 100% main.main /tmp/acat/read-data.go 0 0% 99.15% 0.56s 4.30% go-hep.org/x/hep/rootio.(*File).ReadAt /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/file.go 0 0% 99.15% 0.11s 0.85% go-hep.org/x/hep/rootio.(*Key).load /home/binet/dev/go/gocode/src/ go-hep.org/x/hep/rootio/key.go 0 0% 99.15% 0.56s 4.30% internal/poll.(*FD).Pread /usr/lib/go/src/internal/poll/fd_unix.go 0 0% 99.15% 0.11s 0.85% io.(*SectionReader).Read /usr/lib/go/src/io/io.go 0 0% 99.15% 0.11s 0.85% io.ReadAtLeast /usr/lib/go/src/io/io.go 0 0% 99.15% 0.11s 0.85% io.ReadFull /usr/lib/go/src/io/io.go 0 0% 99.15% 0.56s 4.30% os.(*File).ReadAt /usr/lib/go/src/os/file.go 0 0% 99.15% 0.56s 4.30% os.(*File).pread /usr/lib/go/src/os/file_unix.go 0 0% 99.15% 13.01s 100% runtime.main /usr/lib/go/src/runtime/proc.go 0 0% 99.15% 0.56s 4.30% syscall.Pread /usr/lib/go/src/syscall/zsyscall_linux_amd64.go anything obvious I missed ? cheers, -s -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. 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