[dpdk-users] Using DPDK for contiguous physical memory allocation

[Alain Gautherot <alain@edicogenome.com>]

Hello,

I came across DPDK in a thread @ http://stackoverflow.com/questions/4401912/linux-contiguous-physical-memory-from-userspace (bottom reply from mrsmith) and wanted to see if I can use rte_malloc() to allocate large blocks of contiguous physical memory (16GB or even 32GB at some point).

The platform I'm working on has an FPGA that shares host memory with the x86_64 cores via a QPI link.
The FPGA crunches data directly from host memory and uses physical addresses (mostly a QPI limitation, but it is also dictated by performance considerations and the ability to make the best possible use of multiple memory controllers).
The data shared is 16GB or up to 32GB and could be provided as multiple descriptors to the FPGA, but that still means that each descriptor is in the order of several GBytes each.
I understand that allocation may fail, but is ok for now, since I'm still in the proof-of-concept stage, trying to rule things out.

My sample application attempts to allocate memory by chunks of 100MB like so:

int main(int argc, char **argv)
{
  int ret;

  ret = rte_eal_init(argc, argv);
  if (ret < 0) {
    rte_panic("Cannot init EAL\n");
  }

  int  i;
  for (i = 1; i <= 100; ++i) {
    size_t  allocsize = i * 100*1000*1000;

    printf("  Allocating %3.1fGB: ", ((float )i)/10.0f);
    fflush(stdout);
    void*  ptr = rte_malloc(NULL, allocsize, 0U);
    if (ptr != NULL) {
      printf("PASS\n");
      rte_free(ptr);
    } else {
      printf("fail\n");
    }
  }

  printf("Done\n");
  return 0;
}

I get a consistent crash @ the 2.2GB mark:
(gdb) r -c f -n 4
...
EAL: PCI device 0000:06:00.1 on NUMA socket 0
EAL:   probe driver: 8086:1521 rte_igb_pmd
EAL:   Not managed by a supported kernel driver, skipped
  Allocating 0.1GB: fail
  Allocating 0.2GB: fail
  ...
  Allocating 2.0GB: fail
  Allocating 2.1GB: fail
  Allocating 2.2GB:
Program received signal SIGSEGV, Segmentation fault.
0x00000000004c6770 in malloc_elem_init (elem=0x800070eaa880, heap=0x7ffff7fe561c, mz=0x7ffff7fb2c1c, size=2200000064)
    at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/malloc_elem.c:61
61              elem->heap = heap;
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.149.el6_6.5.x86_64
(gdb) bt
...
#0  0x00000000004c6770 in malloc_elem_init (elem=0x800070eaa880, heap=0x7ffff7fe561c, mz=0x7ffff7fb2c1c, size=2200000064)
    at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/malloc_elem.c:61
#1  0x00000000004c694e in split_elem (elem=0x7ffff3e00000, split_pt=0x800070eaa880) at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/malloc_elem.c:121
#2  0x00000000004c6bda in malloc_elem_alloc (elem=0x7ffff3e00000, size=18446744071614584320, align=64)
    at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/malloc_elem.c:223
#3  0x00000000004c736e in malloc_heap_alloc (heap=0x7ffff7fe561c, type=0x0, size=18446744071614584320, align=64)
    at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/malloc_heap.c:167
#4  0x00000000004c0aa1 in rte_malloc_socket (type=0x0, size=18446744071614584320, align=0, socket_arg=-1)
    at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/rte_malloc.c:89
#5  0x00000000004c0b5b in rte_malloc (type=0x0, size=18446744071614584320, align=0) at /home/alaing/INTEL/dpdk-2.0.0/lib/librte_malloc/rte_malloc.c:115
#6  0x000000000041ca6e in main (argc=5, argv=0x7fffffffdd48) at /home/alaing/INTEL/dpdk-2.0.0/examples/hugephymem/main.c:66


Has anybody seen such an issue?
Could I be misusing RTE somehow?


Thanks for your time,
Alain


--
Alain Gautherot
Edico Genome