First of all, forgive my ignorance regarding ppc64 and if the questions
are naive but after having a
look to the already existing code for ppc64 and this patch now, why are
we doing this reverse mapping at all?
I guess the question revolves around the comment in eal_memory.c:
1316 /* On PPC64 architecture, the mmap always start
from higher
1317 * virtual address to lower address. Here, both the
physical
1318 * address and virtual address are in descending
order */
From looking at the code, for ppc64 we do qsort in reverse order and
thereafter everything looks to be is
done to account for that reverse sorting.
CC: Chao Zhu and David Marchand as original author and reviewer of the code.
Sergio
On 07/03/2016 14:13, Gowrishankar wrote:
> From: Gowri Shankar <gowrishankar.m at linux.vnet.ibm.com>
>
> For a secondary process address space to map hugepages from every segment of
> primary process, hugepage_file entries has to be mapped reversely from the
> list that primary process updated for every segment. This is for a reason
> that,
> in ppc64, hugepages are sorted for decrementing addresses.
>
> Signed-off-by: Gowrishankar <gowrishankar.m at linux.vnet.ibm.com>
> ---
> lib/librte_eal/linuxapp/eal/eal_memory.c | 26 ++++++++++++++++----------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c
> b/lib/librte_eal/linuxapp/eal/eal_memory.c
> index 5b9132c..6aea5d0 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
> @@ -1400,7 +1400,7 @@ rte_eal_hugepage_attach(void)
> {
> const struct rte_mem_config *mcfg =
> rte_eal_get_configuration()->mem_config;
> const struct hugepage_file *hp = NULL;
> - unsigned num_hp = 0;
> + unsigned num_hp = 0, mapped_hp = 0;
> unsigned i, s = 0; /* s used to track the segment number */
> off_t size;
> int fd, fd_zero = -1, fd_hugepage = -1;
> @@ -1486,14 +1486,12 @@ rte_eal_hugepage_attach(void)
> goto error;
> }
>
> - num_hp = size / sizeof(struct hugepage_file);
> - RTE_LOG(DEBUG, EAL, "Analysing %u files\n", num_hp);
> -
> s = 0;
> while (s < RTE_MAX_MEMSEG && mcfg->memseg[s].len > 0){
> void *addr, *base_addr;
> uintptr_t offset = 0;
> size_t mapping_size;
> + unsigned int index;
> #ifdef RTE_LIBRTE_IVSHMEM
> /*
> * if segment has ioremap address set, it's an IVSHMEM segment
> and
> @@ -1504,6 +1502,8 @@ rte_eal_hugepage_attach(void)
> continue;
> }
> #endif
> + num_hp = mcfg->memseg[s].len / mcfg->memseg[s].hugepage_sz;
> + RTE_LOG(DEBUG, EAL, "Analysing %u files in segment %u\n",
> num_hp, s);
> /*
> * free previously mapped memory so we can map the
> * hugepages into the space
> @@ -1514,18 +1514,23 @@ rte_eal_hugepage_attach(void)
> /* find the hugepages for this segment and map them
> * we don't need to worry about order, as the server sorted the
> * entries before it did the second mmap of them */
> +#ifdef RTE_ARCH_PPC_64
> + for (i = num_hp-1; i < num_hp && offset < mcfg->memseg[s].len;
> i--){
> +#else
> for (i = 0; i < num_hp && offset < mcfg->memseg[s].len; i++){
> - if (hp[i].memseg_id == (int)s){
> - fd = open(hp[i].filepath, O_RDWR);
> +#endif
> + index = i + mapped_hp;
> + if (hp[index].memseg_id == (int)s){
> + fd = open(hp[index].filepath, O_RDWR);
> if (fd < 0) {
> RTE_LOG(ERR, EAL, "Could not open %s\n",
> - hp[i].filepath);
> + hp[index].filepath);
> goto error;
> }
> #ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
> - mapping_size = hp[i].size * hp[i].repeated;
> + mapping_size = hp[index].size *
> hp[index].repeated;
> #else
> - mapping_size = hp[i].size;
> + mapping_size = hp[index].size;
> #endif
> addr = mmap(RTE_PTR_ADD(base_addr, offset),
> mapping_size, PROT_READ |
> PROT_WRITE,
> @@ -1534,7 +1539,7 @@ rte_eal_hugepage_attach(void)
> if (addr == MAP_FAILED ||
> addr != RTE_PTR_ADD(base_addr,
> offset)) {
> RTE_LOG(ERR, EAL, "Could not mmap %s\n",
> - hp[i].filepath);
> + hp[index].filepath);
> goto error;
> }
> offset+=mapping_size;
> @@ -1543,6 +1548,7 @@ rte_eal_hugepage_attach(void)
> RTE_LOG(DEBUG, EAL, "Mapped segment %u of size 0x%llx\n", s,
> (unsigned long long)mcfg->memseg[s].len);
> s++;
> + mapped_hp += num_hp;
> }
> /* unmap the hugepage config file, since we are done using it */
> munmap((void *)(uintptr_t)hp, size);
