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.bura...@intel.com>
---
Notes:
v2:
- Detect memfd support at compile time
- Change memfd-related log level to debug
doc/guides/rel_notes/release_19_02.rst | 5 +++
lib/librte_eal/linuxapp/eal/eal_memory.c | 54 +++++++++++++++++++++++-
2 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/doc/guides/rel_notes/release_19_02.rst
b/doc/guides/rel_notes/release_19_02.rst
index 960098582..420d51b5b 100644
--- a/doc/guides/rel_notes/release_19_02.rst
+++ b/doc/guides/rel_notes/release_19_02.rst
@@ -23,6 +23,11 @@ DPDK Release 19.02
New Features
------------
+* **Support for using VirtIO without hugepages**
+
+ The --no-huge mode was augmented to use memfd-backed memory (on systems that
+ support memfd), to allow using VirtIO-based NICs without hugepages.
+
.. This section should contain new features added in this release.
Sample format:
diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c
b/lib/librte_eal/linuxapp/eal/eal_memory.c
index 32feb415d..7d922a965 100644
--- 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;
--
2.17.1
