5.7 KiB
Testing enviornment setup
Install tools:
sudo apt update
sudo apt install -y hyperfine heaptrack valgrind
sudo apt install -y \
build-essential clang lld pkg-config \
linux-perf \
iperf3 netperf net-tools \
tcpdump ethtool iproute2 \
bpftrace bpfcc-tools \
strace ltrace \
sysstat procps \
git perl
Install framegraph(not shipped on debian):
git clone https://github.com/brendangregg/FlameGraph ~/FlameGraph
echo 'export PATH="$HOME/FlameGraph:$PATH"' >> ~/.bashrc
source ~/.bashrc
which flamegraph.pl
modify the Cargo.toml of verion 0.1.0:
[profile.release]
lto = true
codegen-units = 1
debug = 1
strip = "none"
panic = "abort"
Build with frame pointers to help profiling:
git clone https://github.com/DaZuo0122/oxidinetd.git
RUSTFLAGS="-C force-frame-pointers=yes" cargo build --release
profiling.conf:
127.0.0.1 9000 127.0.0.1 9001
Backend iperf3 server:
iperf3 -s -p 9001
forwarder:
./oi -c profiling.conf
triggers redirect:
iperf3 -c 127.0.0.1 -p 9000 -t 30 -P 1
iperf3 -c 127.0.0.1 -p 9000 -t 30 -P 8
verification:
sudo ss -tnp | egrep '(:9000|:9001)'
Testing
CPU hotspot:
sudo perf top -p $(pidof oi)
If you see lots of:
-
sys_read, sys_write, __x64_sys_sendto, tcp_sendmsg → syscall/copy overhead
-
futex, __lll_lock_wait → contention/locks
-
epoll_wait → executor wake behavior / too many idle polls
Hard numbers:
sudo perf stat -p $(pidof oi) -e \
cycles,instructions,cache-misses,branches,branch-misses,context-switches,cpu-migrations \
-- sleep 30
Big differences to watch:
-
context-switches much higher on oi → too many tasks/wakers / lock contention
-
instructions much higher on oi for same throughput → runtime overhead / copies
-
cache-misses higher → allocations / poor locality
Flamegraph
Record:
sudo perf record -F 199 -g -p $(pidof oi) -- sleep 30
sudo perf script | stackcollapse-perf.pl | flamegraph.pl > oi.svg
If the stack looks “flat / missing” (common with async + LTO), use dwarf unwinding:
sudo perf record -F 199 --call-graph dwarf,16384 -p $(pidof oi) -- sleep 30
sudo perf script | stackcollapse-perf.pl | flamegraph.pl > oi.svg
syscall-cost check:
sudo strace -ff -c -p $(pidof oi) -o /tmp/oi.strace
# run 15–30s under load, then Ctrl+C
tail -n +1 /tmp/oi.strace.*
If you see huge % time in read/write/sendmsg/recvmsg, you’re dominated by copying + syscalls.
ebpf stuffs
--skipped--
Smol-focused bottlenecks + the “fix list” A) If you’re syscall/copy bound
Best improvement candidates:
buffer reuse (no per-loop Vec allocation)
reduce tiny writes (coalesce)
zero-copy splice (Linux-only, biggest win but more complex)
For Linux zero-copy, you’d implement a splice(2)-based fast path (socket→pipe→socket). That’s how high-performance forwarders avoid double-copy.
B) If you’re executor/waker bound (common for async forwarders)
Symptoms:
perf shows a lot of runtime / wake / scheduling
perf stat shows more context switches than rinetd
Fixes:
don’t spawn 2 tasks per connection (one per direction) unless needed → do a single task that forwards both directions in one loop (state machine)
avoid any shared Mutex on hot path (logging/metrics)
keep per-conn state minimal
C) If you’re single-thread limited
smol can be extremely fast, but if you’re effectively running everything on one thread, throughput may cap earlier.
Fix direction:
move to smol::Executor + N threads (usually num_cpus)
or run multiple block_on() workers (careful: avoid accept() duplication)
outcome
CPU hotspot
testing commands:
iperf3 -c 127.0.0.1 -p 9000 -t 30 -P 1
sudo perf stat -p $(pidof oi) -e \
cycles,instructions,cache-misses,branches,branch-misses,context-switches,cpu-migrations \
-- sleep 30
perf report:
Performance counter stats for process id '207279':
98,571,874,480 cpu_atom/cycles/ (0.10%)
134,732,064,800 cpu_core/cycles/ (99.90%)
75,889,748,906 cpu_atom/instructions/ # 0.77 insn per cycle (0.10%)
159,098,987,713 cpu_core/instructions/ # 1.18 insn per cycle (99.90%)
30,443,258 cpu_atom/cache-misses/ (0.10%)
3,155,528 cpu_core/cache-misses/ (99.90%)
15,003,063,317 cpu_atom/branches/ (0.10%)
31,479,765,962 cpu_core/branches/ (99.90%)
149,091,165 cpu_atom/branch-misses/ # 0.99% of all branches (0.10%)
195,562,861 cpu_core/branch-misses/ # 0.62% of all branches (99.90%)
1,138 context-switches
37 cpu-migrations
33.004738330 seconds time elapsed
FlameGraph
testing commands:
sudo perf record -F 199 -g -p $(pidof oi) -- sleep 30
sudo perf script | stackcollapse-perf.pl | flamegraph.pl > oi.svg
outcome:
oi.svg
commands:
sudo perf record -F 199 --call-graph dwarf,16384 -p $(pidof oi) -- sleep 30
sudo perf script | stackcollapse-perf.pl | flamegraph.pl > oi_dwarf.svg
outcome:
oi_dwarf.svg
syscall-cost check
sudo strace -ff -c -p $(pidof oi) -o /tmp/oi.strace
# run 15–30s under load, then Ctrl+C
tail -n +1 /tmp/oi.strace.*