Gazelle User Guide


Gazelle is a high-performance user-mode protocol stack. It directly reads and writes NIC packets in user mode based on DPDK and transmit the packets through shared hugepage memory, and uses the LwIP protocol stack. Gazelle greatly improves the network I/O throughput of applications and accelerates the network for the databases, such as MySQL and Redis.

  • High Performance Zero-copy and lock-free packets that can be flexibly scaled out and scheduled adaptively.
  • Universality Compatible with POSIX without modification, and applicable to different types of applications.

In the single-process scenario where the NIC supports multiple queues, is used to shorten the packet path. In other scenarios, the ltran process is used to distribute packets to each thread.


Configure the Yum source of openEuler and run theyum command to install Gazelle.

yum install dpdk
yum install libconfig
yum install numactl
yum install libboundscheck
yum install libpcap
yum install gazelle

NOTE: dpdk >= 21.11-2

How to Use

To configure the operating environment and use Gazelle to accelerate applications, perform the following steps:

1. Installing the .ko File as the root User

Install the .ko files based on the site requirements to enable the virtual network ports and bind NICs to the user-mode driver. To enable the virtual network port function, use rte_kni.ko.

modprobe rte_kni carrier="on"

Bind the NIC from the kernel driver to the user-mode driver. Choose one of the following .ko files based on the site requirements.

#If the IOMMU is available
modprobe vfio-pci

#If the IOMMU is not available and the VFIO supports the no-IOMMU mode
modprobe vfio enable_unsafe_noiommu_mode=1
modprobe vfio-pci

#Other cases
modprobe igb_uio

NOTE: You can check whether the IOMMU is enabled based on the BIOS configuration.

2. Binding the NIC Using DPDK

Bind the NIC to the driver selected in Step 1 to provide an interface for the user-mode NIC driver to access the NIC resources.

#Using vfio-pci
dpdk-devbind -b vfio-pci enp3s0 

#Using igb_uio
dpdk-devbind -b igb_uio enp3s0

3. Configuring Memory Huge Pages

Gazelle uses hugepage memory to improve efficiency. You can configure any size for the memory huge pages reserved by the system using the root permissions. Each memory huge page requires a file descriptor. If the memory is large, you are advised to use 1 GB huge pages to avoid occupying too many file descriptors. Select a page size based on the site requirements and configure sufficient memory huge pages. Run the following commands to configure huge pages:

#Configuring 1024 2 MB huge pages on node0. The total memory is 2 GB.
echo 1024 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages

#Configuring 5 1 GB huge pages on node0. The total memory is 5 GB.
echo 5 > /sys/devices/system/node/node0/hugepages/hugepages-1048576kB/nr_hugepages

NOTE: Run the cat command to query the actual number of reserved pages. If the continuous memory is insufficient, the number may be less than expected.

4. Mounting Memory Huge Pages

Create two directories for the lstack and ltran processes to access the memory huge pages. Run the following commands:

mkdir -p /mnt/hugepages-ltran
mkdir -p /mnt/hugepages-lstack
chmod -R 700 /mnt/hugepages-ltran
chmod -R 700 /mnt/hugepages-lstack

mount -t hugetlbfs nodev /mnt/hugepages-ltran -o pagesize=2M
mount -t hugetlbfs nodev /mnt/hugepages-lstack -o pagesize=2M

NOTE: The huge pages mounted to /mnt/hugepages-ltran and /mnt/hugepages-lstack must be in the same page size.

5. Enabling Gazelle for an Application

Enable Gazelle for an application using either of the following methods as required.

  • Recompile the application and replace the sockets interface.
#Add the Makefile of Gazelle to the application makefile.
-include /etc/gazelle/lstack.Makefile

#Add the LSTACK_LIBS variable when compiling the source code.
gcc test.c -o test ${LSTACK_LIBS}
  • Use the LD_PRELOAD environment variable to load the Gazelle library. Use the GAZELLE_BIND_PROCNAME environment variable to specify the process name, and LD_PRELOAD to specify the Gazelle library path.
GAZELLE_BIND_PROCNAME=test LD_PRELOAD=/usr/lib64/ ./test

6. Configuring Gazelle

  • The lstack.conf file is used to specify the startup parameters of lstack. The default path is /etc/gazelle/lstack.conf. The parameters in the configuration file are as follows:
dpdk_args–socket-mem (mandatory)
–huge-dir (mandatory)
–proc-type (mandatory)
DPDK initialization parameter. For details, see the DPDK description.
–map-perfect is an extended feature. It is used to prevent the DPDK from occupying excessive address space and ensure that extra address space is available for lstack.
The -d option is used to load the specified .so library file.
listen_shadow0/1Whether to use the shadow file descriptor for listening. This function is enabled when there is a single listen thread and multiple protocol stack threads.
use_ltran0/1Whether to use ltran.
num_cpus“0,2,4 …”IDs of the CPUs bound to the lstack threads. The number of IDs is the number of lstack threads (less than or equal to the number of NIC queues). You can select CPUs by NUMA nodes.
num_wakeup“1,3,5 …”IDs of the CPUs bound to the wakeup threads. The number of IDs is the number of wakeup threads, which is the same as the number of lstack threads. Select CPUs of the same NUMA nodes of the num_cpus parameter respectively. If this parameter is not set, the wakeup thread is not used.
low_power_mode0/1Whether to enable the low-power mode. This parameter is not supported currently.
kni_switch0/1Whether to enable the rte_kni module. The default value is 0. This module can be enabled only when ltran is not used.
host_addr“192.168.xx.xx”IP address of the protocol stack, which is also the IP address of the application.
mask_addr“255.255.xx.xx”Subnet mask.
gateway_addr“192.168.xx.1”Gateway address.
devices“aa:bb:cc:dd:ee:ff”MAC address for NIC communication. The value must be the same as that of bond_macs in the ltran.conf file.

lstack.conf example:

dpdk_args=["--socket-mem", "2048,0,0,0", "--huge-dir", "/mnt/hugepages-lstack", "--proc-type", "primary", "--legacy-mem", "--map-perfect"]




  • The ltran.conf file is used to specify ltran startup parameters. The default path is /etc/gazelle/ltran.conf. To enable ltran, set use_ltran=1 in the lstack.conf file. The configuration parameters are as follows:
forward_kit“dpdk”Specified transceiver module of an NIC.
This field is reserved and is not used currently.
–socket-mem (mandatory)
–huge-dir (mandatory)
–proc-TYPE (mandatory)
–legacy-mem (mandatory)
–map-perfect (mandatory)
DPDK initialization parameter. For details, see the DPDK description.
–map-perfect is an extended feature. It is used to prevent the DPDK from occupying excessive address space and ensure that extra address space is available for lstack.
The -d option is used to load the specified .so library file.
kni_switch0/1Whether to enable the rte_kni module. The default value is 0.
dispatch_max_clientsnMaximum number of clients supported by ltran.
The total number of lstack protocol stack threads cannot exceed 32.
dispatch_subnet192.168.xx.xxSubnet mask, which is the subnet segment of the IP addresses that can be identified by ltran. The value is an example. Set the subnet based on the site requirements.
dispatch_subnet_lengthnLength of the Subnet that can be identified by ltran. For example, if the value of length is 4, the value ranges from to
bond_modenBond mode. Currently, only Active Backup(Mode1) is supported. The value is 1.
bond_miimonnBond link monitoring time. The unit is millisecond. The value ranges from 1 to 2^64 - 1 - (1000 x 1000).
bond_ports“0x01”DPDK NIC to be used. The value 0x01 indicates the first NIC.
bond_macs“aa:bb:cc:dd:ee:ff”MAC address of the bound NIC, which must be the same as the MAC address of the KNI.
bond_mtunMaximum transmission unit. The default and maximum value is 1500. The minimum value is 68.

ltran.conf example:

forward_kit_args="-l 0,1 --socket-mem 1024,0,0,0 --huge-dir /mnt/hugepages-ltran --proc-type primary --legacy-mem --map-perfect --syslog daemon"





7. Starting an Application

  • Start the ltran process. If there is only one process and the NIC supports multiple queues, the NIC multi-queue is used to distribute packets to each thread. You do not need to start the ltran process. Set the value of use_ltran in the lstack.conf file to 0. If you do not use -config-file to specify a configuration file when starting ltran, the default configuration file path /etc/gazelle/ltran.conf is used.
ltran --config-file ./ltran.conf
  • Start the application. If the environment variable LSTACK_CONF_PATH is not used to specify the configuration file before the application is started, the default configuration file path /etc/gazelle/lstack.conf is used.
export LSTACK_CONF_PATH=./lstack.conf
LD_PRELOAD=/usr/lib64/  GAZELLE_BIND_PROCNAME=redis-server redis-server redis.conf

8. APIs

Gazelle wraps the POSIX interfaces of the application. The code of the application does not need to be modified.

9. Commissioning Commands

  • If the ltran mode is not used, the gazellectl ltran xxx and gazellectl lstack show {ip | pid} -r commands are not supported.
Usage: gazellectl [-h | help]
  or:  gazellectl ltran  {quit | show | set} [LTRAN_OPTIONS] [time]
  or:  gazellectl lstack {show | set} {ip | pid} [LSTACK_OPTIONS] [time]

  quit            ltran process exit

  where  LTRAN_OPTIONS :=
                  show ltran all statistics
  -r, rate        show ltran statistics per second
  -i, instance    show ltran instance register info
  -b, burst       show ltran NIC packet len per second
  -l, latency     show ltran latency
  loglevel        {error | info | debug} set ltran loglevel

  where  LSTACK_OPTIONS :=
                  show lstack all statistics
  -r, rate        show lstack statistics per second
  -s, snmp        show lstack snmp
  -c, connetct    show lstack connect
  -l, latency     show lstack latency
  loglevel        {error | info | debug} set lstack loglevel
  lowpower        {0 | 1} set lowpower enable
  [time]          measure latency time default 1S

10. Precautions

1. Location of the DPDK Configuration File

For the root user, the configuration file is stored in the /var/run/dpdk directory after the DPDK is started. For a non-root user, the path of the DPDK configuration file is determined by the environment variable XDG_RUNTIME_DIR.

  • If XDG_RUNTIME_DIR is not set, the DPDK configuration file is stored in /tmp/dpdk.
  • If XDG_RUNTIME_DIR is set, the DPDK configuration file is stored in the path specified by XDG_RUNTIME_DIR.
  • Note that XDG_RUNTIME_DIR is set by default on some servers.


Restrictions of Gazelle are as follows:

Function Restrictions

  • Blocking accept() or connect() is not supported.
  • A maximum of 1500 TCP connections are supported.
  • Currently, only TCP, ICMP, ARP, and IPv4 are supported.
  • When a peer end pings Gazelle, the specified packet length must be less than or equal to 14,000 bytes.
  • Transparent huge pages are not supported.
  • ltran does not support the hybrid bonding of multiple types of NICs.
  • The active/standby mode (bond1 mode) of ltran supports active/standby switchover only when a fault occurs at the link layer (for example, the network cable is disconnected), but does not support active/standby switchover when a fault occurs at the physical layer (for example, the NIC is powered off or removed).
  • VM NICs do not support multiple queues.

Operation Constraints

  • By default, the command lines and configuration files provided by Gazelle requires root permissions. Privilege escalation and changing of file owner are required for non-root users.
  • To bind the NIC from user-mode driver back to the kernel driver, you must exit Gazelle first.
  • Memory huge pages cannot be remounted to subdirectories created in the mount point.
  • The minimum huge page memory required by ltran is 1 GB.
  • The minimum hugepage memory of each application instance protocol stack thread is 800 MB.
  • Gazelle supports only 64-bit OSs.
  • The -march=native option is used when building the x86 version of Gazelle to optimize Gazelle based on the CPU instruction set of the build environment (Intel® Xeon® Gold 5118 CPU @ 2.30GHz). Therefore, the CPU of the operating environment must support the SSE4.2, AVX, AVX2, and AVX-512 instruction set extensions.
  • The maximum number of IP fragments is 10 (the maximum ping packet length is 14,790 bytes). TCP does not use IP fragments.
  • You are advised to set the rp_filter parameter of the NIC to 1 using the sysctl command. Otherwise, the Gazelle protocol stack may not be used as expected. Instead, the kernel protocol stack is used.
  • If ltran is not used, the KNI cannot be configured to be used only for local communication. In addition, you need to configure the NetworkManager not to manage the KNI network adapter before starting Gazelle.
  • The IP address and MAC address of the virtual KNI must be the same as those in the lstack.conf file.


You need to evaluate the use of Gazelle based on application scenarios.

Shared Memory

  • Current situation: The memory huge pages are mounted to the /mnt/hugepages-lstack directory. During process initialization, files are created in the /mnt/hugepages-lstack directory. Each file corresponds to a huge page, and the mmap function is performed on the files. After receiving the registration information of lstask, ltran also perform the mmap function on the file in the directory based on the huge page memory configuration information to implement shared huge page memory. The procedure also applies to the files in the /mnt/hugepages-ltran directory.
  • Current mitigation measures The huge page file permission is 600. Only the owner can access the files. The default owner is the root user. Other users can be configured. Huge page files are locked by DPDK and cannot be directly written or mapped.
  • Caution Malicious processes belonging to the same user imitate the DPDK implementation logic to share huge page memory using huge page files and perform write operations to damage the huge page memory. As a result, the Gazelle program crashes. It is recommended that the processes of a user belong to the same trust domain.

Traffic Limit Gazelle does not limit the traffic. Users can send packets at the maximum NIC line rate to the network, which may congest the network.

Process Spoofing If two lstack processes A and B are legitimately registered with ltran, A can impersonate B to send spoofing messages to ltran and modify the ltran forwarding control information. As a result, the communication of B becomes abnormal, and information leakage occurs when packets for B are sent to A. Ensure that all lstack processes are trusted.

Bug Catching

Buggy Content

Bug Description

Submit As Issue

It's a little complicated....

I'd like to ask someone.


Just a small problem.

I can fix it online!

Bug Type
Specifications and Common Mistakes

● Misspellings or punctuation mistakes;

● Incorrect links, empty cells, or wrong formats;

● Chinese characters in English context;

● Minor inconsistencies between the UI and descriptions;

● Low writing fluency that does not affect understanding;

● Incorrect version numbers, including software package names and version numbers on the UI.


● Incorrect or missing key steps;

● Missing prerequisites or precautions;

● Ambiguous figures, tables, or texts;

● Unclear logic, such as missing classifications, items, and steps.


● Technical principles, function descriptions, or specifications inconsistent with those of the software;

● Incorrect schematic or architecture diagrams;

● Incorrect commands or command parameters;

● Incorrect code;

● Commands inconsistent with the functions;

● Wrong screenshots.

Risk Warnings

● Lack of risk warnings for operations that may damage the system or important data.

Content Compliance

● Contents that may violate applicable laws and regulations or geo-cultural context-sensitive words and expressions;

● Copyright infringement.

How satisfied are you with this document

Not satisfied at all
Very satisfied
Click to create an issue. An issue template will be automatically generated based on your feedback.