Then, the main() function is called. The core initialization and launch is done in rte_eal_init() (see the API documentation).
It consist of calls to the pthread library (more specifically, pthread_self(), pthread_create(), and pthread_setaffinity_np()).
-.. _figure_linuxapp_launch:
+.. _figure_linux_launch:
.. figure:: img/linuxapp_launch.*
.. note::
Initialization of objects, such as memory zones, rings, memory pools, lpm tables and hash tables,
- should be done as part of the overall application initialization on the master lcore.
+ should be done as part of the overall application initialization on the main lcore.
The creation and initialization functions for these objects are not multi-thread safe.
However, once initialized, the objects themselves can safely be used in multiple threads simultaneously.
Multi-process Support
~~~~~~~~~~~~~~~~~~~~~
-The Linuxapp EAL allows a multi-process as well as a multi-threaded (pthread) deployment model.
+The Linux EAL allows a multi-process as well as a multi-threaded (pthread) deployment model.
See chapter
:ref:`Multi-process Support <Multi-process_Support>` for more details.
Memory Mapping Discovery and Memory Reservation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The allocation of large contiguous physical memory is done using the hugetlbfs kernel filesystem.
+The allocation of large contiguous physical memory is done using hugepages.
The EAL provides an API to reserve named memory zones in this contiguous memory.
The physical address of the reserved memory for that memory zone is also returned to the user by the memory zone reservation API.
.. note::
- Memory reservations done using the APIs provided by rte_malloc are also backed by pages from the hugetlbfs filesystem.
+ Memory reservations done using the APIs provided by rte_malloc
+ are also backed by hugepages unless ``--no-huge`` option is given.
-+ Dynamic memory mode
+Dynamic Memory Mode
+^^^^^^^^^^^^^^^^^^^
-Currently, this mode is only supported on Linux.
+Currently, this mode is only supported on Linux and Windows.
In this mode, usage of hugepages by DPDK application will grow and shrink based
on application's requests. Any memory allocation through ``rte_malloc()``,
``--socket-limit`` command-line option, for a simple way to limit maximum amount
of memory that can be used by DPDK application.
-+ Legacy memory mode
+.. warning::
+ Memory subsystem uses DPDK IPC internally, so memory allocations/callbacks
+ and IPC must not be mixed: it is not safe to allocate/free memory inside
+ memory-related or IPC callbacks, and it is not safe to use IPC inside
+ memory-related callbacks. See chapter
+ :ref:`Multi-process Support <Multi-process_Support>` for more details about
+ DPDK IPC.
+
+Legacy Memory Mode
+^^^^^^^^^^^^^^^^^^
This mode is enabled by specifying ``--legacy-mem`` command-line switch to the
EAL. This switch will have no effect on FreeBSD as FreeBSD only supports
If neither ``-m`` nor ``--socket-mem`` were specified, the entire available
hugepage memory will be preallocated.
-+ Hugepage allocation matching
+Hugepage Allocation Matching
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This behavior is enabled by specifying the ``--match-allocations`` command-line
switch to the EAL. This switch is Linux-only and not supported with
requirements. This can result in some increased memory usage which is
very dependent on the memory allocation patterns of the application.
-+ 32-bit support
+32-bit Support
+^^^^^^^^^^^^^^
Additional restrictions are present when running in 32-bit mode. In dynamic
memory mode, by default maximum of 2 gigabytes of VA space will be preallocated,
-and all of it will be on master lcore NUMA node unless ``--socket-mem`` flag is
+and all of it will be on main lcore NUMA node unless ``--socket-mem`` flag is
used.
In legacy mode, VA space will only be preallocated for segments that were
requested (plus padding, to keep IOVA-contiguousness).
-+ Maximum amount of memory
+Maximum Amount of Memory
+^^^^^^^^^^^^^^^^^^^^^^^^
All possible virtual memory space that can ever be used for hugepage mapping in
a DPDK process is preallocated at startup, thereby placing an upper limit on how
of virtual memory being preallocated at startup by editing the following config
variables:
-* ``CONFIG_RTE_MAX_MEMSEG_LISTS`` controls how many segment lists can DPDK have
-* ``CONFIG_RTE_MAX_MEM_MB_PER_LIST`` controls how much megabytes of memory each
+* ``RTE_MAX_MEMSEG_LISTS`` controls how many segment lists can DPDK have
+* ``RTE_MAX_MEM_MB_PER_LIST`` controls how much megabytes of memory each
segment list can address
-* ``CONFIG_RTE_MAX_MEMSEG_PER_LIST`` controls how many segments each segment can
- have
-* ``CONFIG_RTE_MAX_MEMSEG_PER_TYPE`` controls how many segments each memory type
+* ``RTE_MAX_MEMSEG_PER_LIST`` controls how many segments each segment list
+ can have
+* ``RTE_MAX_MEMSEG_PER_TYPE`` controls how many segments each memory type
can have (where "type" is defined as "page size + NUMA node" combination)
-* ``CONFIG_RTE_MAX_MEM_MB_PER_TYPE`` controls how much megabytes of memory each
+* ``RTE_MAX_MEM_MB_PER_TYPE`` controls how much megabytes of memory each
memory type can address
-* ``CONFIG_RTE_MAX_MEM_MB`` places a global maximum on the amount of memory
+* ``RTE_MAX_MEM_MB`` places a global maximum on the amount of memory
DPDK can reserve
Normally, these options do not need to be changed.
can later be mapped into that preallocated VA space (if dynamic memory mode
is enabled), and can optionally be mapped into it at startup.
+Hugepage Mapping
+^^^^^^^^^^^^^^^^
+
+Below is an overview of methods used for each OS to obtain hugepages,
+explaining why certain limitations and options exist in EAL.
+See the user guide for a specific OS for configuration details.
+
+FreeBSD uses ``contigmem`` kernel module
+to reserve a fixed number of hugepages at system start,
+which are mapped by EAL at initialization using a specific ``sysctl()``.
+
+Windows EAL allocates hugepages from the OS as needed using Win32 API,
+so available amount depends on the system load.
+It uses ``virt2phys`` kernel module to obtain physical addresses,
+unless running in IOVA-as-VA mode (e.g. forced with ``--iova-mode=va``).
+
+Linux allows to select any combination of the following:
+
+* use files in hugetlbfs (the default)
+ or anonymous mappings (``--in-memory``);
+* map each hugepage from its own file (the default)
+ or map multiple hugepages from one big file (``--single-file-segments``).
+
+Mapping hugepages from files in hugetlbfs is essential for multi-process,
+because secondary processes need to map the same hugepages.
+EAL creates files like ``rtemap_0``
+in directories specified with ``--huge-dir`` option
+(or in the mount point for a specific hugepage size).
+The ``rte`` prefix can be changed using ``--file-prefix``.
+This may be needed for running multiple primary processes
+that share a hugetlbfs mount point.
+Each backing file by default corresponds to one hugepage,
+it is opened and locked for the entire time the hugepage is used.
+This may exhaust the number of open files limit (``NOFILE``).
+See :ref:`segment-file-descriptors` section
+on how the number of open backing file descriptors can be reduced.
+
+In dynamic memory mode, EAL removes a backing hugepage file
+when all pages mapped from it are freed back to the system.
+However, backing files may persist after the application terminates
+in case of a crash or a leak of DPDK memory (e.g. ``rte_free()`` is missing).
+This reduces the number of hugepages available to other processes
+as reported by ``/sys/kernel/mm/hugepages/hugepages-*/free_hugepages``.
+EAL can remove the backing files after opening them for mapping
+if ``--huge-unlink`` is given to avoid polluting hugetlbfs.
+However, since it disables multi-process anyway,
+using anonymous mapping (``--in-memory``) is recommended instead.
+
+:ref:`EAL memory allocator <malloc>` relies on hugepages being zero-filled.
+Hugepages are cleared by the kernel when a file in hugetlbfs or its part
+is mapped for the first time system-wide
+to prevent data leaks from previous users of the same hugepage.
+EAL ensures this behavior by removing existing backing files at startup
+and by recreating them before opening for mapping (as a precaution).
+
+One exception is ``--huge-unlink=never`` mode.
+It is used to speed up EAL initialization, usually on application restart.
+Clearing memory constitutes more than 95% of hugepage mapping time.
+EAL can save it by remapping existing backing files
+with all the data left in the mapped hugepages ("dirty" memory).
+Such segments are marked with ``RTE_MEMSEG_FLAG_DIRTY``.
+Memory allocator detects dirty segments and handles them accordingly,
+in particular, it clears memory requested with ``rte_zmalloc*()``.
+In this mode EAL also does not remove a backing file
+when all pages mapped from it are freed,
+because they are intended to be reusable at restart.
+
+Anonymous mapping does not allow multi-process architecture.
+This mode does not use hugetlbfs
+and thus does not require root permissions for memory management
+(the limit of locked memory amount, ``MEMLOCK``, still applies).
+It is free of filename conflict and leftover file issues.
+If ``memfd_create(2)`` is supported both at build and run time,
+DPDK memory manager can provide file descriptors for memory segments,
+which are required for VirtIO with vhost-user backend.
+This can exhaust the number of open files limit (``NOFILE``)
+despite not creating any visible files.
+See :ref:`segment-file-descriptors` section
+on how the number of open file descriptors used by EAL can be reduced.
+
+.. _segment-file-descriptors:
+
+Segment File Descriptors
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+On Linux, in most cases, EAL will store segment file descriptors in EAL. This
+can become a problem when using smaller page sizes due to underlying limitations
+of ``glibc`` library. For example, Linux API calls such as ``select()`` may not
+work correctly because ``glibc`` does not support more than certain number of
+file descriptors.
+
+There are two possible solutions for this problem. The recommended solution is
+to use ``--single-file-segments`` mode, as that mode will not use a file
+descriptor per each page, and it will keep compatibility with Virtio with
+vhost-user backend. This option is not available when using ``--legacy-mem``
+mode.
+
+Another option is to use bigger page sizes. Since fewer pages are required to
+cover the same memory area, fewer file descriptors will be stored internally
+by EAL.
+
Support for Externally Allocated Memory
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ Using heap API's for externally allocated memory
-Using using a set of malloc heap API's is the recommended way to use externally
+Using a set of malloc heap API's is the recommended way to use externally
allocated memory in DPDK. In this way, support for externally allocated memory
is implemented through overloading the socket ID - externally allocated heaps
will have socket ID's that would be considered invalid under normal
These API's are (as their name implies) intended to allow registering or
unregistering externally allocated memory to/from DPDK's internal page table, to
-allow API's like ``rte_virt2memseg`` etc. to work with externally allocated
+allow API's like ``rte_mem_virt2memseg`` etc. to work with externally allocated
memory. Memory added this way will not be available for any regular DPDK
allocators; DPDK will leave this memory for the user application to manage.
- If IOVA table is not specified, IOVA addresses will be assumed to be
unavailable
- Other processes must attach to the memory area before they can use it
-* Perform DMA mapping with ``rte_vfio_dma_map`` if needed
+* Perform DMA mapping with ``rte_dev_dma_map`` if needed
* Use the memory area in your application
* If memory area is no longer needed, it can be unregistered
- If the area was mapped for DMA, unmapping must be performed before
The RX interrupt is the first choice to be such kind of wake-up event, but probably won't be the only one.
EAL provides the event APIs for this event-driven thread mode.
-Taking linuxapp as an example, the implementation relies on epoll. Each thread can monitor an epoll instance
+Taking Linux as an example, the implementation relies on epoll. Each thread can monitor an epoll instance
in which all the wake-up events' file descriptors are added. The event file descriptors are created and mapped to
the interrupt vectors according to the UIO/VFIO spec.
-From bsdapp's perspective, kqueue is the alternative way, but not implemented yet.
+From FreeBSD's perspective, kqueue is the alternative way, but not implemented yet.
EAL initializes the mapping between event file descriptors and interrupt vectors, while each device initializes the mapping
between interrupt vectors and queues. In this way, EAL actually is unaware of the interrupt cause on the specific vector.
callback. Care must be taken not to close the device from the interrupt handler
context. It is necessary to reschedule such closing operation.
-Blacklisting
-~~~~~~~~~~~~
+Block list
+~~~~~~~~~~
-The EAL PCI device blacklist functionality can be used to mark certain NIC ports as blacklisted,
+The EAL PCI device block list functionality can be used to mark certain NIC ports as unavailable,
so they are ignored by the DPDK.
-The ports to be blacklisted are identified using the PCIe* description (Domain:Bus:Device.Function).
+The ports to be blocked are identified using the PCIe* description (Domain:Bus:Device.Function).
Misc Functions
~~~~~~~~~~~~~~
Locks and atomic operations are per-architecture (i686 and x86_64).
+IOVA Mode Detection
+~~~~~~~~~~~~~~~~~~~
+
+IOVA Mode is selected by considering what the current usable Devices on the
+system require and/or support.
+
+On FreeBSD, RTE_IOVA_PA is always the default. On Linux, the IOVA mode is
+detected based on a 2-step heuristic detailed below.
+
+For the first step, EAL asks each bus its requirement in terms of IOVA mode
+and decides on a preferred IOVA mode.
+
+- if all buses report RTE_IOVA_PA, then the preferred IOVA mode is RTE_IOVA_PA,
+- if all buses report RTE_IOVA_VA, then the preferred IOVA mode is RTE_IOVA_VA,
+- if all buses report RTE_IOVA_DC, no bus expressed a preference, then the
+ preferred mode is RTE_IOVA_DC,
+- if the buses disagree (at least one wants RTE_IOVA_PA and at least one wants
+ RTE_IOVA_VA), then the preferred IOVA mode is RTE_IOVA_DC (see below with the
+ check on Physical Addresses availability),
+
+If the buses have expressed no preference on which IOVA mode to pick, then a
+default is selected using the following logic:
+
+- if physical addresses are not available, RTE_IOVA_VA mode is used
+- if /sys/kernel/iommu_groups is not empty, RTE_IOVA_VA mode is used
+- otherwise, RTE_IOVA_PA mode is used
+
+In the case when the buses had disagreed on their preferred IOVA mode, part of
+the buses won't work because of this decision.
+
+The second step checks if the preferred mode complies with the Physical
+Addresses availability since those are only available to root user in recent
+kernels. Namely, if the preferred mode is RTE_IOVA_PA but there is no access to
+Physical Addresses, then EAL init fails early, since later probing of the
+devices would fail anyway.
+
+.. note::
+
+ The RTE_IOVA_VA mode is preferred as the default in most cases for the
+ following reasons:
+
+ - All drivers are expected to work in RTE_IOVA_VA mode, irrespective of
+ physical address availability.
+ - By default, the mempool, first asks for IOVA-contiguous memory using
+ ``RTE_MEMZONE_IOVA_CONTIG``. This is slow in RTE_IOVA_PA mode and it may
+ affect the application boot time.
+ - It is easy to enable large amount of IOVA-contiguous memory use cases
+ with IOVA in VA mode.
+
+ It is expected that all PCI drivers work in both RTE_IOVA_PA and
+ RTE_IOVA_VA modes.
+
+ If a PCI driver does not support RTE_IOVA_PA mode, the
+ ``RTE_PCI_DRV_NEED_IOVA_AS_VA`` flag is used to dictate that this PCI
+ driver can only work in RTE_IOVA_VA mode.
+
+ When the KNI kernel module is detected, RTE_IOVA_PA mode is preferred as a
+ performance penalty is expected in RTE_IOVA_VA mode.
+
IOVA Mode Configuration
~~~~~~~~~~~~~~~~~~~~~~~
To facilitate forcing the IOVA mode to a specific value the EAL command line option ``--iova-mode`` can
be used to select either physical addressing('pa') or virtual addressing('va').
+.. _max_simd_bitwidth:
+
+
+Max SIMD bitwidth
+~~~~~~~~~~~~~~~~~
+
+The EAL provides a single setting to limit the max SIMD bitwidth used by DPDK,
+which is used in determining the vector path, if any, chosen by a component.
+The value can be set at runtime by an application using the
+'rte_vect_set_max_simd_bitwidth(uint16_t bitwidth)' function,
+which should only be called once at initialization, before EAL init.
+The value can be overridden by the user using the EAL command-line option '--force-max-simd-bitwidth'.
+
+When choosing a vector path, along with checking the CPU feature support,
+the value of the max SIMD bitwidth must also be checked, and can be retrieved using the
+'rte_vect_get_max_simd_bitwidth()' function.
+The value should be compared against the enum values for accepted max SIMD bitwidths:
+
+.. code-block:: c
+
+ enum rte_vect_max_simd {
+ RTE_VECT_SIMD_DISABLED = 64,
+ RTE_VECT_SIMD_128 = 128,
+ RTE_VECT_SIMD_256 = 256,
+ RTE_VECT_SIMD_512 = 512,
+ RTE_VECT_SIMD_MAX = INT16_MAX + 1,
+ };
+
+ if (rte_vect_get_max_simd_bitwidth() >= RTE_VECT_SIMD_512)
+ /* Take AVX-512 vector path */
+ else if (rte_vect_get_max_simd_bitwidth() >= RTE_VECT_SIMD_256)
+ /* Take AVX2 vector path */
+
+
Memory Segments and Memory Zones (memzone)
------------------------------------------
non-EAL pthread support
~~~~~~~~~~~~~~~~~~~~~~~
-It is possible to use the DPDK execution context with any user pthread (aka. Non-EAL pthreads).
-In a non-EAL pthread, the *_lcore_id* is always LCORE_ID_ANY which identifies that it is not an EAL thread with a valid, unique, *_lcore_id*.
-Some libraries will use an alternative unique ID (e.g. TID), some will not be impacted at all, and some will work but with limitations (e.g. timer and mempool libraries).
+It is possible to use the DPDK execution context with any user pthread (aka. non-EAL pthreads).
+There are two kinds of non-EAL pthreads:
+
+- a registered non-EAL pthread with a valid *_lcore_id* that was successfully assigned by calling ``rte_thread_register()``,
+- a non registered non-EAL pthread with a LCORE_ID_ANY,
+
+For non registered non-EAL pthread (with a LCORE_ID_ANY *_lcore_id*), some libraries will use an alternative unique ID (e.g. TID), some will not be impacted at all, and some will work but with limitations (e.g. timer and mempool libraries).
All these impacts are mentioned in :ref:`known_issue_label` section.
- with affinity restricted to 2-4, the Control Threads will end up on
CPU 4.
- with affinity restricted to 2-3, the Control Threads will end up on
- CPU 2 (master lcore, which is the default when no CPU is available).
+ CPU 2 (main lcore, which is the default when no CPU is available).
.. _known_issue_label:
+ rte_mempool
The rte_mempool uses a per-lcore cache inside the mempool.
- For non-EAL pthreads, ``rte_lcore_id()`` will not return a valid number.
- So for now, when rte_mempool is used with non-EAL pthreads, the put/get operations will bypass the default mempool cache and there is a performance penalty because of this bypass.
- Only user-owned external caches can be used in a non-EAL context in conjunction with ``rte_mempool_generic_put()`` and ``rte_mempool_generic_get()`` that accept an explicit cache parameter.
+ For unregistered non-EAL pthreads, ``rte_lcore_id()`` will not return a valid number.
+ So for now, when rte_mempool is used with unregistered non-EAL pthreads, the put/get operations will bypass the default mempool cache and there is a performance penalty because of this bypass.
+ Only user-owned external caches can be used in an unregistered non-EAL context in conjunction with ``rte_mempool_generic_put()`` and ``rte_mempool_generic_get()`` that accept an explicit cache parameter.
+ rte_ring
rte_ring supports multi-producer enqueue and multi-consumer dequeue.
- However, it is non-preemptive, this has a knock on effect of making rte_mempool non-preemptable.
+ However, it is non-preemptive, this has a knock on effect of making rte_mempool non-preemptible.
.. note::
5. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR.
+ Alternatively, applications can use the lock-free stack mempool handler. When
+ considering this handler, note that:
+
+ - It is currently limited to the aarch64 and x86_64 platforms, because it uses
+ an instruction (16-byte compare-and-swap) that is not yet available on other
+ platforms.
+ - It has worse average-case performance than the non-preemptive rte_ring, but
+ software caching (e.g. the mempool cache) can mitigate this by reducing the
+ number of stack accesses.
+
+ rte_timer
- Running ``rte_timer_manage()`` on a non-EAL pthread is not allowed. However, resetting/stopping the timer from a non-EAL pthread is allowed.
+ Running ``rte_timer_manage()`` on an unregistered non-EAL pthread is not allowed. However, resetting/stopping the timer from a non-EAL pthread is allowed.
+ rte_log
- In non-EAL pthreads, there is no per thread loglevel and logtype, global loglevels are used.
+ In unregistered non-EAL pthreads, there is no per thread loglevel and logtype, global loglevels are used.
+ misc
- The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in a non-EAL pthread.
+ The debug statistics of rte_ring, rte_mempool and rte_timer are not supported in an unregistered non-EAL pthread.
cgroup control
~~~~~~~~~~~~~~
echo 100000 > pkt_io/cpu.cfs_period_us
echo 50000 > pkt_io/cpu.cfs_quota_us
+.. _malloc:
Malloc
------
Refer to the rte_malloc() function description in the *DPDK API Reference*
manual for more information.
-Cookies
-~~~~~~~
-
-When CONFIG_RTE_MALLOC_DEBUG is enabled, the allocated memory contains
-overwrite protection fields to help identify buffer overflows.
Alignment and NUMA Constraints
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Malloc heap is a doubly-linked list, where each element keeps track of its
previous and next elements. Due to the fact that hugepage memory can come and
-go, neighbouring malloc elements may not necessarily be adjacent in memory.
+go, neighboring malloc elements may not necessarily be adjacent in memory.
Also, since a malloc element may span multiple pages, its contents may not
necessarily be IOVA-contiguous either - each malloc element is only guaranteed
to be virtually contiguous.
In that case, the pad header is used to locate the actual malloc element
header for the block.
+* dirty - this flag is only meaningful when ``state`` is ``FREE``.
+ It indicates that the content of the element is not fully zero-filled.
+ Memory from such blocks must be cleared when requested via ``rte_zmalloc*()``.
+ Dirty elements only appear with ``--huge-unlink=never``.
+
* pad - this holds the length of the padding present at the start of the block.
In the case of a normal block header, it is added to the address of the end
of the header to give the address of the start of the data area, i.e. the
git.droids-corp.org / dpdk.git / blobdiff