Failure while allocating 1GB hugepages

[Antonio Di Bacco]

Just in case I need, let us say, 1.5 GB CONTIGUOUS memory zone,
would it be fine to use something like this as GRUB config in Linux?

default_hugepagesz=2G hugepagesz=2G hugepages=4"


On Wed, May 22, 2024 at 12:22 PM Antonio Di Bacco
<a.dibacco.ks at gmail.com> wrote:
>
> That was really useful. Thx
>
> On Fri, May 10, 2024 at 5:07 PM Dmitry Kozlyuk <dmitry.kozliuk at gmail.com> wrote:
> >
> > 2024-05-10 11:33 (UTC+0200), Antonio Di Bacco:
> > > I have 16 hugepages available per NUMA on a 4 NUMA system:
> > >
> > > [user at node-1 hugepages]$ cat
> > > /sys/devices/system/node/*/hugepages/hugepages-1048576kB/free_hugepages
> > > 16
> > > 16
> > > 16
> > > 16
> > >
> > > Using the following program with dpdk 21.11, sometimes I can allocate
> > > a few pages but most of the time I cannot. I tried also to remove
> > > rtemap_* under /dev/hugepages.
> > > rte_memzone_reserve_aligned is always supposed to use a new page?
> > >
> > > #include <stdio.h>
> > > #include <rte_eal.h>
> > > #include <rte_memzone.h>
> > >
> > > #include <rte_errno.h>
> > > #include <unistd.h>
> > >
> > > int main(int argc, char **argv)
> > > {
> > >     const struct rte_memzone *mz;
> > >     int ret;
> > >     printf("pid: %d\n", getpid());
> > >     // Initialize EAL
> > >     ret = rte_eal_init(argc, argv);
> > >     if (ret < 0) {
> > >         fprintf(stderr, "Error with EAL initialization\n");
> > >         return -1;
> > >     }
> > >
> > >     for (int socket = 0; socket < 4; socket++)
> > >     {
> > >       for (int i = 0; i < 16; i++)
> > >       {
> > >         // Allocate memory using rte_memzone_reserve_aligned
> > >         char name[32];
> > >         sprintf(name, "my_memzone%d-%d", i, socket);
> > >         mz = rte_memzone_reserve_aligned(name, 1ULL << 30, socket,
> > > RTE_MEMZONE_IOVA_CONTIG, 1ULL << 30);
> > >
> > >         if (mz == NULL) {
> > >           printf("errno %s\n", rte_strerror(rte_errno));
> > >           fprintf(stderr, "Memory allocation failed\n");
> > >           rte_eal_cleanup();
> > >           return -1;
> > >       }
> > >
> > >       printf("Memory allocated with name %s at socket %d physical
> > > address: %p, addr %p addr64 %lx size: %zu\n", name, mz->socket_id,
> > > (mz->iova), mz->addr, mz->addr_64, mz->len);
> > >     }
> > >     }
> > >
> > >     // Clean up EAL
> > >     rte_eal_cleanup();
> > >     return 0;
> > > }
> >
> > Hi Antonio,
> >
> > Does it succeed without RTE_MEMZONE_IOVA_CONTIG?
> > If so, does your system/app have ASLR enabled?
> >
> > When memzone size is 1G and hugepage size is 1G,
> > two hugepages are required: one for the requested amount of memory,
> > and one for memory allocator element header,
> > which does not fit into the same page obviously.
> > I suspect that two allocated hugepages get non-continuous IOVA
> > and that's why the function fails.
> > There are no useful logs in EAL to check the suspicion,
> > but you can hack elem_check_phys_contig() in malloc_elem.c.