Darwin debugging for the Linux developer

These technical notes are meant to explain to a Linux developer what are the equivalents to debug certain things over Darwin.
Key differences from Linux
Linux tool
macOS equivalent
Purpose
strace
dtruss (1), 
strace-macos
System call tracing
perf
sample, 
spindump, 
Instruments (2)
Performance profiling
ss
netstat -nv
Socket statistics
iostat
iostat -Id
Disk I/O statistics
lsof
lsof
Open file listings
/proc
vmmap, 
heap, 
lsof
Process/memory information
blktrace
fs_usage -wf filesys
Trace real-time IO activity
(1): 
dtruss is unavailable on systems with System Integrity Protection enabled (SIP). Lix CI machines have SIP enabled.
(2): 
Instruments is a graphical application that requires a remote desktop and cannot be used over SSH.
Getting flamegraphs out of 
sample
Combine https://github.com/brc7/flamegraph-sample/blob/master/stackcollapse-sample.py with https://speedscope.app/.
Inspecting memory allocations
heap can give a list of allocations sorted by sizes when it can recognize the type in-memory (doesn't always work for everything).
iostat tips
iostat -Id on macOS will return as the first row the cumulative data SINCE the first boot.
xfrs := IO operations per second.
Listing file descriptors
/proc doesn't exist on macOS, therefore, 
lsof is the only thing that can list file descriptors and let you understand the relationships.
Tracing network activity
fs_usage -wf network can trace real-time network activity on file descriptors.
Checking Internet quality
networkQuality -v will dump an Apple-infrastructure Internet connection check for bandwidth and latency.