Bcachefs cache hit ratio

bcachefs_hit_ratio.py

#!/usr/bin/env python3
import os
import glob
import sys

# Base directory for the bcachefs instance.
BASE_DIR = '/sys/fs/bcachefs/' + sys.argv[1]

def format_bytes(num_bytes):
    """
    Convert a number of bytes into a human-readable string using binary units.
    """
    num = float(num_bytes)
    for unit in ['B', 'KiB', 'MiB', 'GiB', 'TiB']:
        if num < 1024:
            return f"{num:.2f} {unit}"
        num /= 1024
    return f"{num:.2f} PiB"

def parse_io_done(file_path):
    """
    Parse an io_done file.
    The file is expected to have two sections ("read:" and "write:")
    followed by lines with "key : value" pairs.
    
    Returns a dict with keys "read" and "write", each mapping to a dict of counters.
    """
    results = {"read": {}, "write": {}}
    current_section = None
    try:
        with open(file_path, "r") as f:
            for line in f:
                line = line.strip()
                if not line:
                    continue
                # Detect section headers.
                if line.lower() in ("read:", "write:"):
                    current_section = line[:-1].lower()  # remove trailing colon
                    continue

                if current_section is None:
                    continue

                # Expect lines like "metric : value"
                if ':' in line:
                    key_part, value_part = line.split(":", 1)
                    key = key_part.strip()
                    try:
                        value = int(value_part.strip())
                    except ValueError:
                        value = 0
                    results[current_section][key] = value
    except Exception as e:
        print(f"Error reading {file_path}: {e}")
    return results

def main():
    # In your system, the devices appear as dev-* directories.
    dev_paths = glob.glob(os.path.join(BASE_DIR, "dev-*"))
    if not dev_paths:
        print("No dev-* directories found!")
        return

    # We'll build a nested structure to hold our aggregated metrics.
    # The structure is:
    #
    # group_data = {
    #    <group>: {
    #         "read": {
    #              "totals": { metric: sum_value, ... },
    #              "devices": {
    #                     <device_label>: { metric: value, ... },
    #                     ...
    #              }
    #         },
    #         "write": { similar structure }
    #    },
    #    ...
    # }
    group_data = {}
    overall = {"read": 0, "write": 0}

    for dev_path in dev_paths:
        # Each dev-* directory must have a label file.
        label_file = os.path.join(dev_path, "label")
        if not os.path.isfile(label_file):
            continue
        try:
            with open(label_file, "r") as f:
                content = f.read().strip()
                # Expect a label like "ssd.ssd1"
                parts = content.split('.')
                if len(parts) >= 2:
                    group = parts[0].strip()
                    dev_label = parts[1].strip()
                else:
                    group = content.strip()
                    dev_label = content.strip()
        except Exception as e:
            print(f"Error reading {label_file}: {e}")
            continue

        # Look for an io_done file in the same directory.
        io_file = os.path.join(dev_path, "io_done")
        if not os.path.isfile(io_file):
            # If no io_done, skip this device.
            continue

        io_data = parse_io_done(io_file)

        # Initialize the group if not already present.
        if group not in group_data:
            group_data[group] = {
                "read": {"totals": {}, "devices": {}},
                "write": {"totals": {}, "devices": {}}
            }
        # Register this device under the group for both read and write.
        for section in ("read", "write"):
            if dev_label not in group_data[group][section]["devices"]:
                group_data[group][section]["devices"][dev_label] = {}

        # Process each section (read and write).
        for section in ("read", "write"):
            for metric, value in io_data.get(section, {}).items():
                # Update group totals.
                group_totals = group_data[group][section]["totals"]
                group_totals[metric] = group_totals.get(metric, 0) + value

                # Update per-device breakdown.
                dev_metrics = group_data[group][section]["devices"][dev_label]
                dev_metrics[metric] = dev_metrics.get(metric, 0) + value

    # Compute overall totals for read and write across all groups.
    for group in group_data:
        for section in ("read", "write"):
            section_total = sum(group_data[group][section]["totals"].values())
            overall[section] += section_total

    # Now print the aggregated results.
    print("=== bcachefs I/O Metrics Grouped by Device Group ===\n")
    for group in sorted(group_data.keys()):
        print(f"Group: {group}")
        for section in ("read", "write"):
            section_total = sum(group_data[group][section]["totals"].values())
            overall_section_total = overall[section]
            percent_overall = (section_total / overall_section_total * 100) if overall_section_total > 0 else 0
            print(f"  {section.capitalize()} I/O: {format_bytes(section_total)} ({percent_overall:.2f}% overall)")

            totals = group_data[group][section]["totals"]
            for metric in sorted(totals.keys()):
                metric_total = totals[metric]
                # Build a breakdown string by device for this metric.
                breakdown_entries = []
                for dev_label, metrics in sorted(group_data[group][section]["devices"].items()):
                    dev_value = metrics.get(metric, 0)
                    pct = (dev_value / metric_total * 100) if metric_total > 0 else 0
                    breakdown_entries.append(f"{pct:.2f}% by {dev_label}")
                breakdown_str = ", ".join(breakdown_entries)
                print(f"      {metric:<12}: {format_bytes(metric_total)} ({breakdown_str})")
            print()  # blank line after section
        print()  # blank line after group

if __name__ == "__main__":
    main()

Remember to adjust your BASE_DIR in line 6!

Thanks! I changed a little.

--- a/bcachefs_hit_ratio.py	2025-02-04 13:22:07.600998325 +0300
+++ b/bcachefs_hit_ratio.py	2025-02-04 13:21:03.164592981 +0300
@@ -1,9 +1,10 @@
 #!/usr/bin/env python3
 import os
 import glob
+import sys
 
 # Base directory for the bcachefs instance.
-BASE_DIR = "/sys/fs/bcachefs/20b15bfd-e996-4f45-8ab6-07b15bd9bae7"
+BASE_DIR = '/sys/fs/bcachefs/' + sys.argv[1]
 
 def format_bytes(num_bytes):
     """

Thanks! I changed a little.

Thanks! I updated the gist