Stable Low Latency Machines

Trying to do software performance testing on a noisy development machine can have challenges, especially when the code under test uses multiple cores and the operating system or other processes wishes to use some of the CPU cores. My Windows OS development setup was not quiet, enough so that I’m writing this. Dealing with noise and other latency adding processes makes the machine overall much more responsive and pleasant to use.

Windows Clean Up Scripts

Probably the noisiest thing about a Windows machine is just all the default services and background processes that are running. There are various scripts that strip down a default Windows 10 install for privacy focussed reasons and people have naturally combined these Windows 10 clean up scripts in different ways. This win10script that I forked on github does a good job of turning off many services that are not necessary and uninstalling various bits of bloatware. It’s also handy for installing all the programs you want via the chocolatey package manager on that new windows install.

The most controversial tweak I made is turning off the real time anti-virus scanning. That was an annoyance, needing to find the registry setting to edit as the scanning turns itself back on automatically otherwise. Development environments like Intellij even offer to add your software project directories to the scanning exclusion list, so it’s clearly annoying some people. I might have ignored it and not noticed it except it was often the top CPU consumer in an otherwise quiet system and more frustratingly it makes the Thunderbird email client really slow and stuttering even whilst typing new messages (and still pretty slow after finding the Thunderbird play-nice-with-antivirus option).

A non-service related tweak was to disable all the animations/fades/delays in the “adjust the appearance and performance of windows” options. Maybe overkill, but it’s nice not to wait for animations when trying to get familiar stuff done quickly. That’s a similar tension that is seen between animation heavy web UI component libraries like Material UI and more snappier ones such as Bulma.

simplewall

To control and reduce network traffic you could use something like glasswire but simplewall works just fine and blocks all outbound traffic unless you allow it (pop ups ask if you want to let the process start outbound traffic).

Process priority and CPU Affinity

Running the process being performance tested with high scheduler priority may help a little. It’s possible to get some more performance consistency by limiting the process to certain CPUs so cached data is unlikely to jump around to different L1/L2 CPU caches. By disallowing the process from using all the cores the operating system should have a better idea to use those unused cores for other processes that may interrupt the process under test.

After struggling with the windows cmd.exe shell commands, I’d probably try with powershell and Create-Process / Set-Affinity commands next time, but this one works well enough except you cannot Ctrl-C terminate the process (but can use Ctrl+Break):

start "Benchmark" /HIGH /AFFINITY 1F /WAIT /B path/to/executable

The affinity is a bit mask as a hexadecimal number, one bit per logical cpu core, e.g. bits 1—12 for a 12 core CPU.

Other Low Latency Experiences

Speeding up performance tests soon meant I wanted to remove any other sluggish tools on the system or to improve them.

The Cmder command line console is very likeable in terms of features and fast once going, but it took ~5 seconds to open a new tab, for the sake of features that I don’t use. One /f start up flag (see the windows terminal config) and it’s down to 1 second.

The new windows terminal is a nice modern GPU accelerated terminal that works fine with Cmder via a little config. It’ll be even better when I can open a new tab as Admin instead of having to start a new terminal as Admin.

The PowerToys project is mostly about small useful utilities, but the PowerToys Run certainly seems quicker than the normal start menu when you know what you want.

There could be a side rant on the bloat of Electron based tooling like VSCode (though it’s not that bad for what it does). I’ll certainly see how viable sublime text 4 will be (when it’s released) as a python/rust programming editor given how fast and low latency it is. 4Coder is super fast but for C++ only (including scripted in C/C++) at the moment and in Beta, still planning to add Rust support later.

Sublime Merge is certainly a low latency nice git client, but whether people can be tempted to use a client outside of their IDE or just use the command line, it’s hard to say.

Opening PDFs barely seems worth mentioning, but in the past Adobe has always been very slow and bloated. I’ve been using SumatraPDF for years now. Fast software should do the job (read PDFs) and nothing more.