Add io-profile: bpftrace-based IO + CPU profiling wrapper

Wraps any command and produces a standardized report with block IO
metrics, syscall tracking (fsync, O_DIRECT), CPU utilization, and
per-thread breakdown. Supports optional JSON output.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pykello

README.md

@@ -2,6 +2,8 @@
 
 Minimal-overhead I/O benchmarking tool using [libblkio](https://gitlab.com/libblkio/libblkio). Designed for benchmarking vhost-user-blk backends (e.g., ubiblk) with busy-loop polling and direct libblkio calls.
 
+Also includes `io-profile`, a bpftrace-based IO + CPU profiling wrapper that can wrap any command (including blkbench) to produce a system-level profile.
+
 ## Build
 
 Prerequisites: libblkio (installed with pkg-config support), GCC, pthreads.
@@ -128,6 +130,76 @@ blkbench: rw=randread, bs=4k, iodepth=32, numjobs=4, runtime=10s
   ios: total=3200000, errors=0, flushes=0
 ```
 
+## io-profile
+
+A reusable IO + CPU profiling wrapper. Runs any command and produces a standardized report with block IO metrics, syscall tracking, CPU utilization, and per-thread breakdown.
+
+Requires: `bpftrace` (root), `iostat`, `mpstat`, `awk`.
+
+### Usage
+
+```bash
+sudo ./io-profile [options] -- command [args...]
+```
+
+### Options
+
+| Arg | Default | Description |
+|-----|---------|-------------|
+| `-o, --output DIR` | `./io-profile-results` | Output directory for reports |
+| `-d, --device DEV` | auto-detect | Block device to monitor |
+| `-p, --pid PID` | | Only trace this PID and children |
+| `--json` | off | Also emit machine-readable JSON summary |
+| `-v, --verbose` | off | Show progress messages |
+
+### Examples
+
+Profile a blkbench run:
+```bash
+sudo ./io-profile --json -o results/ -- \
+  ./blkbench --driver io_uring --path /tmp/test-disk.raw --rw randread --bs 4k --iodepth 32 --runtime 10
+```
+
+Profile any command:
+```bash
+sudo ./io-profile -d nvme0n1 -- fio job.fio
+sudo ./io-profile -- dd if=/dev/zero of=/tmp/test bs=1M count=1000
+```
+
+### What it collects
+
+- **Block IO**: throughput, IOPS, queue depth distribution, block size distribution, IO latency percentiles, sequential vs random ratio, read/write split
+- **Syscalls**: fsync/fdatasync/sync_file_range counts and rates, O_DIRECT detection
+- **CPU**: utilization percentiles, iowait, user/system split, context switch rate
+- **Per-thread**: IOPS, read/write bytes, fsync count, sequential percentage per thread
+
+### Example output
+
+```
+=== IO Profile: ./blkbench --driver io_uring --path /tmp/test-disk.raw --rw randread ... ===
+Duration: 10.2s | Device: nvme0n1 | Kernel: 6.8.0-94-generic
+
+IO Summary:
+  Throughput:    Read 1250.3 MB/s | Write 0.0 MB/s
+  IOPS:          Read 320,012 | Write 0
+  IO Threads:    4
+  R/W Ratio:     100% read / 0% write
+  Sequential:    12%
+  fsync calls:   0 (0.0/s)
+  O_DIRECT:      Yes (4 opens)
+
+Histograms:
+  Queue Depth:   p25=28   p50=31   p75=32   p99=32   max=32
+  Block Size:    p25=4K   p50=4K   p75=4K   p99=4K   max=4K
+  IO Latency:    p25=8us  p50=12us p75=18us p99=45us max=850us
+
+CPU Summary:
+  CPU Usage:     p25=22% p50=25% p75=28% p99=35%
+  IOWait:        p25=0%  p50=0%  p75=1%  p99=2%
+  User/System:   25% user / 0% system
+  Ctx Switches:  12,340/s
+```
+
 ## Architecture
 
 - **Threading**: One thread per job, each with its own libblkio queue — no shared mutable state during the benchmark.