For more information, please refer to :ref:`DPDK Getting Started Guide <linux_gsg>`.
-If I want to change the number of TLB Hugepages allocated, how do I remove the original pages allocated?
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+If I want to change the number of hugepages allocated, how do I remove the original pages allocated?
+----------------------------------------------------------------------------------------------------
The number of pages allocated can be seen by executing the following command::
If you look in the directory, you will see ``n`` number of 2M pages files. If you specified 1024, you will see 1024 page files.
These are then placed in memory segments to get contiguous memory.
-If you need to change the number of pages, it is easier to first remove the pages. The tools/dpdk-setup.sh script provides an option to do this.
+If you need to change the number of pages, it is easier to first remove the pages. The usertools/dpdk-setup.sh script provides an option to do this.
See the "Quick Start Setup Script" section in the :ref:`DPDK Getting Started Guide <linux_gsg>` for more information.
-If I execute "l2fwd -c f -m 64 -n 3 -- -p 3", I get the following output, indicating that there are no socket 0 hugepages to allocate the mbuf and ring structures to?
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+If I execute "l2fwd -l 0-3 -m 64 -n 3 -- -p 3", I get the following output, indicating that there are no socket 0 hugepages to allocate the mbuf and ring structures to?
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------
I have set up a total of 1024 Hugepages (that is, allocated 512 2M pages to each NUMA node).
I am running a 32-bit DPDK application on a NUMA system, and sometimes the application initializes fine but cannot allocate memory. Why is that happening?
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-32-bit applications have limitations in terms of how much virtual memory is available, hence the number of hugepages they are able to allocate is also limited (1 GB per page size).
-If your system has a lot (>1 GB per page size) of hugepage memory, not all of it will be allocated.
+32-bit applications have limitations in terms of how much virtual memory is available, hence the number of hugepages they are able to allocate is also limited (1 GB size).
+If your system has a lot (>1 GB size) of hugepage memory, not all of it will be allocated.
Due to hugepages typically being allocated on a local NUMA node, the hugepages allocation the application gets during the initialization depends on which
NUMA node it is running on (the EAL does not affinitize cores until much later in the initialization process).
Sometimes, the Linux OS runs the DPDK application on a core that is located on a different NUMA node from DPDK master core and
therefore all the hugepages are allocated on the wrong socket.
-To avoid this scenario, either lower the amount of hugepage memory available to 1 GB per page size (or less), or run the application with taskset
+To avoid this scenario, either lower the amount of hugepage memory available to 1 GB size (or less), or run the application with taskset
affinitizing the application to a would-be master core.
For example, if your EAL coremask is 0xff0, the master core will usually be the first core in the coremask (0x10); this is what you have to supply to taskset::
- taskset 0x10 ./l2fwd -c 0xff0 -n 2
+ taskset 0x10 ./l2fwd -l 4-11 -n 2
+
+.. Note: Instead of '-c 0xff0' use the '-l 4-11' as a cleaner way to define lcores.
In this way, the hugepages have a greater chance of being allocated to the correct socket.
Additionally, a ``--socket-mem`` option could be used to ensure the availability of memory for each socket, so that if hugepages were allocated on
Similarly, the application can be tuned to have, on average, a low end-to-end latency at the cost of lower throughput.
To achieve higher throughput, the DPDK attempts to aggregate the cost of processing each packet individually by processing packets in bursts.
-Using the testpmd application as an example, the "burst" size can be set on the command line to a value of 16 (also the default value).
-This allows the application to request 16 packets at a time from the PMD.
-The testpmd application then immediately attempts to transmit all the packets that were received, in this case, all 16 packets.
+Using the testpmd application as an example, the "burst" size can be set on the command line to a value of 32 (also the default value).
+This allows the application to request 32 packets at a time from the PMD.
+The testpmd application then immediately attempts to transmit all the packets that were received, in this case, all 32 packets.
The packets are not transmitted until the tail pointer is updated on the corresponding TX queue of the network port.
This behavior is desirable when tuning for high throughput because the cost of tail pointer updates to both the RX and TX queues
-can be spread across 16 packets, effectively hiding the relatively slow MMIO cost of writing to the PCIe* device.
+can be spread across 32 packets, effectively hiding the relatively slow MMIO cost of writing to the PCIe* device.
-However, this is not very desirable when tuning for low latency, because the first packet that was received must also wait for the other 15 packets to be received.
-It cannot be transmitted until the other 15 packets have also been processed because the NIC will not know to transmit the packets until the TX tail pointer has been updated,
-which is not done until all 16 packets have been processed for transmission.
+However, this is not very desirable when tuning for low latency, because the first packet that was received must also wait for the other 31 packets to be received.
+It cannot be transmitted until the other 31 packets have also been processed because the NIC will not know to transmit the packets until the TX tail pointer has been updated,
+which is not done until all 32 packets have been processed for transmission.
To consistently achieve low latency even under heavy system load, the application developer should avoid processing packets in bunches.
The testpmd application can be configured from the command line to use a burst value of 1.
------------------------------------------------------------------
See the Primary and Secondary examples in the :ref:`multi-process sample application <multi_process_app>`.
+
+
+Why can't my application receive packets on my system with UEFI Secure Boot enabled?
+------------------------------------------------------------------------------------
+
+If UEFI secure boot is enabled, the Linux kernel may disallow the use of UIO on the system.
+Therefore, devices for use by DPDK should be bound to the ``vfio-pci`` kernel module rather than ``igb_uio`` or ``uio_pci_generic``.
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