mem: use memfd for no-huge mode

When running in no-huge mode, we anonymously allocate our memory.
While this works for regular NICs and vdev's, it's not suitable
for memory sharing scenarios such as virtio with vhost_user
backend.

To fix this, allocate no-huge memory using memfd, and register
it with memalloc just like any other memseg fd. This will enable
using rte_memseg_get_fd() API with --no-huge EAL flag.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/doc/guides/rel_notes/release_19_02.rst b/doc/guides/rel_notes/release_19_02.rst
index 010cac1..46863c5 100644 (file)
--- a/doc/guides/rel_notes/release_19_02.rst
+++ b/doc/guides/rel_notes/release_19_02.rst
@@ -69,6 +69,11 @@ New Features
   chunks of external memory to be registered with DPDK without adding them to
   the malloc heap.
 
+* **Support for using virtio-user without hugepages**
+
+  The --no-huge mode was augmented to use memfd-backed memory (on systems that
+  support memfd), to allow using virtio-user-based NICs without hugepages.
+
 * **Updated the enic driver.**
 
   * Added support for ``RTE_ETH_DEV_CLOSE_REMOVE`` flag.

diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
index 32feb41..7d922a9 100644 (file)
--- a/lib/librte_eal/linuxapp/eal/eal_memory.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
@@ -25,6 +25,10 @@
 #include <sys/time.h>
 #include <signal.h>
 #include <setjmp.h>
+#ifdef F_ADD_SEALS /* if file sealing is supported, so is memfd */
+#include <linux/memfd.h>
+#define MEMFD_SUPPORTED
+#endif
 #ifdef RTE_EAL_NUMA_AWARE_HUGEPAGES
 #include <numa.h>
 #include <numaif.h>
@@ -1341,12 +1345,18 @@ eal_legacy_hugepage_init(void)
        /* hugetlbfs can be disabled */
        if (internal_config.no_hugetlbfs) {
                struct rte_memseg_list *msl;
+               int n_segs, cur_seg, fd, flags;
+#ifdef MEMFD_SUPPORTED
+               int memfd;
+#endif
                uint64_t page_sz;
-               int n_segs, cur_seg;
 
                /* nohuge mode is legacy mode */
                internal_config.legacy_mem = 1;
 
+               /* nohuge mode is single-file segments mode */
+               internal_config.single_file_segments = 1;
+
                /* create a memseg list */
                msl = &mcfg->memsegs[0];
 
@@ -1359,8 +1369,38 @@ eal_legacy_hugepage_init(void)
                        return -1;
                }
 
+               /* set up parameters for anonymous mmap */
+               fd = -1;
+               flags = MAP_PRIVATE | MAP_ANONYMOUS;
+
+#ifdef MEMFD_SUPPORTED
+               /* create a memfd and store it in the segment fd table */
+               memfd = memfd_create("nohuge", 0);
+               if (memfd < 0) {
+                       RTE_LOG(DEBUG, EAL, "Cannot create memfd: %s\n",
+                                       strerror(errno));
+                       RTE_LOG(DEBUG, EAL, "Falling back to anonymous map\n");
+               } else {
+                       /* we got an fd - now resize it */
+                       if (ftruncate(memfd, internal_config.memory) < 0) {
+                               RTE_LOG(ERR, EAL, "Cannot resize memfd: %s\n",
+                                               strerror(errno));
+                               RTE_LOG(ERR, EAL, "Falling back to anonymous map\n");
+                               close(memfd);
+                       } else {
+                               /* creating memfd-backed file was successful.
+                                * we want changes to memfd to be visible to
+                                * other processes (such as vhost backend), so
+                                * map it as shared memory.
+                                */
+                               RTE_LOG(DEBUG, EAL, "Using memfd for anonymous memory\n");
+                               fd = memfd;
+                               flags = MAP_SHARED;
+                       }
+               }
+#endif
                addr = mmap(NULL, internal_config.memory, PROT_READ | PROT_WRITE,
-                               MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+                               flags, fd, 0);
                if (addr == MAP_FAILED) {
                        RTE_LOG(ERR, EAL, "%s: mmap() failed: %s\n", __func__,
                                        strerror(errno));
@@ -1371,6 +1411,16 @@ eal_legacy_hugepage_init(void)
                msl->socket_id = 0;
                msl->len = internal_config.memory;
 
+               /* we're in single-file segments mode, so only the segment list
+                * fd needs to be set up.
+                */
+               if (fd != -1) {
+                       if (eal_memalloc_set_seg_list_fd(0, fd) < 0) {
+                               RTE_LOG(ERR, EAL, "Cannot set up segment list fd\n");
+                               /* not a serious error, proceed */
+                       }
+               }
+
                /* populate memsegs. each memseg is one page long */
                for (cur_seg = 0; cur_seg < n_segs; cur_seg++) {
                        arr = &msl->memseg_arr;