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