Establish baseline performance

In this section you will start by setting up a baseline configuration before using advanced techniques to tune the performance of network workloads.

Optimal baseline configuration before tuning

This includes:

• Aligning the IOMMU settings with default Ubuntu settings
• Setting up a default configuration
• Disabling access logging
• Setting up an optimal thread count

Align the IOMMU settings with default Ubuntu settings

1. To change the IOMMU settings, use a text editor to modify the grub file by adding or updating the GRUB_CMDLINE_LINUX configuration:

    

        
        
sudo vi /etc/default/grub

    

Depending on what’s in your grub file you will need to add or update GRUB_CMDLINE_LINUX:

    

        
        
GRUB_CMDLINE_LINUX="iommu.strict=1 iommu.passthrough=0"

    

2. Update GRUB and reboot your system to apply the default settings.

    

        
        
sudo update-grub && sudo reboot

    

3. Verify that the default settings have been successfully applied:

    

        
        
sudo dmesg | grep iommu

    

You should see that under the default configuration, iommu.strict is enabled, and iommu.passthrough is disabled:

    

        
        [    0.877401] iommu: Default domain type: Translated (set via kernel command line)
[    0.877404] iommu: DMA domain TLB invalidation policy: strict mode (set via kernel command line)
...

        
    

Establish a baseline configuration on Arm Neoverse bare-metal instances

1. To set the remaining CPU cores on your instance to be offline, run:

    

        
        
for no in {8..191}; do sudo bash -c "echo 0 > /sys/devices/system/cpu/cpu${no}/online"; done

    

2. Use the following commands to verify that cores 0-7 are online and the remaining cores are offline.

    

        
        
lscpu

    

The output should look like:

    

        
        Architecture:                aarch64
  CPU op-mode(s):            64-bit
  Byte Order:                Little Endian
CPU(s):                      192
  On-line CPU(s) list:       0-7
  Off-line CPU(s) list:      8-191
Vendor ID:                   ARM
  Model name:                Neoverse-V2
...

        
    

3. Now shutdown and restart Tomcat on your Arm Neoverse bare-metal instance as shown:

    

        
        
~/apache-tomcat-11.0.10/bin/shutdown.sh 2>/dev/null
ulimit -n 65535 && ~/apache-tomcat-11.0.10/bin/startup.sh

    

4. On your x86_64 bare-metal instance, run wrk2 as shown:

    

        
        
ulimit -n 65535 && wrk -c1280 -t128 -R500000 -d60 http://${tomcat_ip}:8080/examples/servlets/servlet/HelloWorldExample

    

Replace {tomcat_ip} in the command above with the IP address of your Arm-based instance where the Tomcat server is running.

The result with this baseline configuration should look like:

    

        
          Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    16.76s     6.59s   27.56s    56.98%
    Req/Sec     1.97k   165.05     2.33k    89.90%
  14680146 requests in 1.00m, 7.62GB read
  Socket errors: connect 1264, read 0, write 0, timeout 1748
Requests/sec: 244449.62
Transfer/sec:    129.90MB

        
    

Disable Access logging

To disable access logging, use a text editor to modify the server.xml file by commenting out or removing the org.apache.catalina.valves.AccessLogValve configuration.

The file is at:

    

        
        
vi ~/apache-tomcat-11.0.10/conf/server.xml

    

Either comment out or delete the configuration shown at the end of the file:

    

        
        
<!-- 
    <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
        prefix="localhost_access_log" suffix=".txt"
        pattern="%h %l %u %t &quot;%r&quot; %s %b" />
-->

    

1. Shutdown and restart Tomcat on your Arm Neoverse bare-metal instance as shown:

    

        
        
~/apache-tomcat-11.0.10/bin/shutdown.sh 2>/dev/null
ulimit -n 65535 && ~/apache-tomcat-11.0.10/bin/startup.sh

    

2. Run wrk2 on the x86_64 bare-metal instance:

    

        
        
ulimit -n 65535 && wrk -c1280 -t128 -R500000 -d60 http://${tomcat_ip}:8080/examples/servlets/servlet/HelloWorldExample

    

The result with access logging disabled should look like:

    

        
        
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    16.16s     6.45s   28.26s    57.85%
    Req/Sec     2.16k     5.91     2.17k    77.50%
  16291136 requests in 1.00m, 8.45GB read
  Socket errors: connect 0, read 0, write 0, timeout 75
Requests/sec: 271675.12
Transfer/sec:    144.36MB

    

Set up optimal thread counts

To minimize resource contention between threads and overhead from thread context switching, the number of CPU-intensive threads in Tomcat should be aligned with the number of CPU cores.

1. When using wrk to perform pressure testing on Tomcat, use top to identify the CPU-intensive threads :

    

        
        
top -H -p$(pgrep java)

    

The output from top will look like:

    

        
        
top - 08:57:29 up 20 min,  1 user,  load average: 4.17, 2.35, 1.22
Threads: 231 total,   8 running, 223 sleeping,   0 stopped,   0 zombie
%Cpu(s): 31.7 us, 20.2 sy,  0.0 ni, 31.0 id,  0.0 wa,  0.0 hi, 17.2 si,  0.0 st
MiB Mem : 386127.8 total, 380676.0 free,   4040.7 used,   2801.1 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used. 382087.0 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
   4677 ubuntu    20   0   36.0g   1.4g  24452 R  89.0   0.4   1:18.71 http-nio-8080-P
   4685 ubuntu    20   0   36.0g   1.4g  24452 R   4.7   0.4   0:04.42 http-nio-8080-A
   4893 ubuntu    20   0   36.0g   1.4g  24452 S   3.3   0.4   0:00.60 http-nio-8080-e
   4963 ubuntu    20   0   36.0g   1.4g  24452 S   3.3   0.4   0:00.66 http-nio-8080-e
   4924 ubuntu    20   0   36.0g   1.4g  24452 S   3.0   0.4   0:00.59 http-nio-8080-e
   4955 ubuntu    20   0   36.0g   1.4g  24452 S   3.0   0.4   0:00.60 http-nio-8080-e
   5061 ubuntu    20   0   36.0g   1.4g  24452 S   3.0   0.4   0:00.61 http-nio-8080-e
   4895 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.58 http-nio-8080-e
   4907 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.59 http-nio-8080-e
   4940 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.58 http-nio-8080-e
   4946 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.59 http-nio-8080-e
   4956 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.65 http-nio-8080-e
   4959 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.59 http-nio-8080-e
   4960 ubuntu    20   0   36.0g   1.4g  24452 R   2.7   0.4   0:00.60 http-nio-8080-e
   4962 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.57 http-nio-8080-e
   4982 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.63 http-nio-8080-e
   4983 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.58 http-nio-8080-e
   4996 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.60 http-nio-8080-e
   5033 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.59 http-nio-8080-e
   5036 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.66 http-nio-8080-e
   5056 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.61 http-nio-8080-e
   5065 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.56 http-nio-8080-e
   5068 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.61 http-nio-8080-e
   5070 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.60 http-nio-8080-e
   5071 ubuntu    20   0   36.0g   1.4g  24452 S   2.7   0.4   0:00.61 http-nio-8080-e
...

    

You can observe from the output that http-nio-8080-e and http-nio-8080-P threads are CPU-intensive. As the http-nio-8080-P thread is fixed at 1 in current version of Tomcat, and the current number of CPU cores is 8, the http-nio-8080-e thread count should be configured to 7.

To configure the http-nio-8080-e thread count, use a text editor to modify the server.xml file and update the <Connector port="8080" protocol="HTTP/1.1" configuration.

The file is at:

    

        
        
vi ~/apache-tomcat-11.0.10/conf/server.xml

    

Replace the existing Connector setting as shown:

    

        
        
<!-- Before -->
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />

    

With the updated setting:

    

        
        
<!-- After -->
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443"
               minSpareThreads="7"
               maxThreads="7"
               maxKeepAliveRequests="500000"
               maxConnections="100000"
    />

    

Save the changes to server.xml.

2. Now shutdown and restart Tomcat on your Arm Neoverse bare-metal instance as shown:

    

        
        
~/apache-tomcat-11.0.10/bin/shutdown.sh 2>/dev/null
ulimit -n 65535 && ~/apache-tomcat-11.0.10/bin/startup.sh

    

3. Run wrk2 on thex86_64 bare-metal instance:

    

        
        
ulimit -n 65535 && wrk -c1280 -t128 -R500000 -d60 http://${tomcat_ip}:8080/examples/servlets/servlet/HelloWorldExample

    

The result with the optimal thread count settings should look like:

    

        
          Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    10.26s     4.55s   19.81s    62.51%
    Req/Sec     2.86k    89.49     3.51k    77.06%
  21458421 requests in 1.00m, 11.13GB read
Requests/sec: 357835.75
Transfer/sec:    190.08MB

        
    

Now that you have established some baseline settings you can proceed to further tuning your setup.