Hi all,
I wrote a script to dump out various stats about a bcache. It would be nice
eventually to put it into bcache-tools so that users don't have to go digging
through sysfs, but for now I'm really just wondering, does this program
interpret the sysfs files correctly?
I'm particularly anxious about 'cache used' since it's just reading out of
/sys/fs/bcache/*/cache*/priority_stats and multiplying by cache size...
...also I wonder what the negative dirty data count means?
$ bcache-status -s
--- bcache ---
Device /dev/bcache0 (253:0)
UUID c4157b48-5cdc-4554-8ce6-520dafdbac55
Block Size 4.00KiB
Bucket Size 512.00KiB
Congested? False
Read Congestion 2.0ms
Write Congestion 20.0ms
Total Cache Size 205.66GiB
Total Cache Used 26.74GiB (12%)
Total Cache Unused 178.92GiB (87%)
Dirty Data 0B (0%)
Evictable Cache 205.66GiB (100%)
Replacement Policy [lru] fifo random
Cache Mode writethrough [writeback] writearound none
Total Hits 263809 (56%)
Total Misses 199136
Total Bypass Hits 9079 (100%)
Total Bypass Misses 0
Total Bypassed 2.70GiB
--- Backing Device ---
Device /dev/sdb1 (8:17)
Size 698.64GiB
Cache Mode writethrough [writeback] writearound none
Readahead 0
Sequential Cutoff 4.00MiB
Merge sequential? True
State dirty
Writeback? True
Dirty Data -2.10MiB
Total Hits 263809 (56%)
Total Misses 199136
Total Bypass Hits 9079 (100%)
Total Bypass Misses 0
Total Bypassed 2.60GiB
--- Cache Device ---
Device /dev/sda4 (8:4)
Size 205.66GiB
Block Size 4.00KiB
Bucket Size 512.00KiB
Replacement Policy [lru] fifo random
Discard? False
I/O Errors 0
Metadata Written 1.10GiB
Data Written 25.30GiB
Buckets 421190
Cache Used 26.74GiB (12%)
Cache Unused 178.92GiB (87%)
--D
#!/usr/bin/env python3
# Dumb script to dump (some) of bcache status
# Copyright 2013 Darrick J. Wong. All rights reserved.
# This program is licensed under GPLv2.
import os
import sys
MAX_KEY_LENGTH = 28
def file_to_lines(fname):
try:
with open(fname, "r") as fd:
return fd.readlines()
except:
return []
def file_to_line(fname):
ret = file_to_lines(fname)
if len(ret) > 0:
return ret[0].strip()
return ''
def str_to_bool(x):
if x == '1':
return True
return False
def format_sectors(x):
'''Pretty print a sector count.'''
sectors = int(x)
asectors = abs(sectors)
if asectors == 0:
return '0B'
elif asectors < 2048:
return '%.2fKiB' % (sectors / 2)
elif asectors < 2097152:
return '%.2fMiB' % (sectors / 2048)
elif asectors < 2147483648:
return '%.2fGiB' % (sectors / 2097152)
else:
return '%.2fTiB' % (sectors / 2147483648)
def interpret_sectors(x):
'''Interpret a pretty-printed disk size.'''
factors = {
'k': 1 << 10,
'M': 1 << 20,
'G': 1 << 30,
'T': 1 << 40,
'P': 1 << 50,
'E': 1 << 60,
'Z': 1 << 70,
'Y': 1 << 80,
}
factor = 1
if x[-1] in factors:
factor = factors[x[-1]]
x = x[:-1]
return int(float(x) * factor / 512)
def pretty_size(x):
return format_sectors(interpret_sectors(x))
def dump_bdev(bdev_path):
'''Dump a backing device stats.'''
global MAX_KEY_LENGTH, devnum_map
attrs = [
('../dev', 'Device', lambda x: '%s (%s)' % (devnum_map.get(x, '?'), x)),
('../size', 'Size', format_sectors),
('cache_mode', 'Cache Mode', None),
('readahead', 'Readahead', None),
('sequential_cutoff', 'Sequential Cutoff', pretty_size),
('sequential_merge', 'Merge sequential?', str_to_bool),
('state', 'State', None),
('writeback_running', 'Writeback?', str_to_bool),
('dirty_data', 'Dirty Data', pretty_size),
]
print('--- Backing Device ---')
for (sysfs_name, display_name, conversion_func) in attrs:
val = file_to_line('%s/%s' % (bdev_path, sysfs_name))
if conversion_func is not None:
val = conversion_func(val)
if display_name is None:
display_name = sysfs_name
print(' %-*s%s' % (MAX_KEY_LENGTH - 2, display_name, val))
def dump_cachedev(cachedev_path):
'''Dump a cachding device stats.'''
def fmt_cachesize(val):
return '%s\t(%d%%)' % (format_sectors(val), float(val) / cache_size * 100)
global MAX_KEY_LENGTH, devnum_map
attrs = [
('../dev', 'Device', lambda x: '%s (%s)' % (devnum_map.get(x, '?'), x)),
('../size', 'Size', format_sectors),
('block_size', 'Block Size', pretty_size),
('bucket_size', 'Bucket Size', pretty_size),
('cache_replacement_policy', 'Replacement Policy', None),
('discard', 'Discard?', str_to_bool),
('io_errors', 'I/O Errors', None),
('metadata_written', 'Metadata Written', pretty_size),
('written', 'Data Written', pretty_size),
('nbuckets', 'Buckets', None),
(None, 'Cache Used', lambda x: fmt_cachesize(used_sectors)),
(None, 'Cache Unused', lambda x: fmt_cachesize(unused_sectors)),
]
stats = get_cache_priority_stats(cachedev_path)
cache_size = int(file_to_line('%s/../size' % cachedev_path))
unused_sectors = float(stats['Unused'][:-1]) * cache_size / 100
used_sectors = cache_size - unused_sectors
print('--- Cache Device ---')
for (sysfs_name, display_name, conversion_func) in attrs:
if sysfs_name is not None:
val = file_to_line('%s/%s' % (cachedev_path, sysfs_name))
if conversion_func is not None:
val = conversion_func(val)
if display_name is None:
display_name = sysfs_name
print(' %-*s%s' % (MAX_KEY_LENGTH - 2, display_name, val))
def hits_to_str(hits_str, misses_str):
'''Render a hits/misses ratio as a string.'''
hits = int(hits_str)
misses = int(misses_str)
ret = '%d' % hits
if hits + misses != 0:
ret = '%s\t(%.d%%)' % (ret, 100 * hits / (hits + misses))
return ret
def dump_stats(sysfs_path, indent_str, stats):
'''Dump stats on a bcache device.'''
stat_types = [
('five_minute', 'Last 5min'),
('hour', 'Last Hour'),
('day', 'Last Day'),
('total', 'Total'),
]
attrs = ['bypassed', 'cache_bypass_hits', 'cache_bypass_misses', 'cache_hits', 'cache_misses']
display = [
('Hits', lambda: hits_to_str(stat_data['cache_hits'], stat_data['cache_misses'])),
('Misses', lambda: stat_data['cache_misses']),
('Bypass Hits', lambda: hits_to_str(stat_data['cache_bypass_hits'], stat_data['cache_bypass_misses'])),
('Bypass Misses', lambda: stat_data['cache_bypass_misses']),
('Bypassed', lambda: pretty_size(stat_data['bypassed'])),
]
for (sysfs_name, stat_display_name) in stat_types:
if len(stats) > 0 and sysfs_name not in stats:
continue
stat_data = {}
for attr in attrs:
val = file_to_line('%s/stats_%s/%s' % (sysfs_path, sysfs_name, attr))
stat_data[attr] = val
for (display_name, str_func) in display:
d = '%s%s %s' % (indent_str, stat_display_name, display_name)
print('%-*s%s' % (MAX_KEY_LENGTH, d, str_func()))
def get_cache_priority_stats(cache):
'''Retrieve priority stats from a cache.'''
attrs = {}
for line in file_to_lines('%s/priority_stats' % cache):
x = line.split()
key = x[0]
value = x[1]
attrs[key[:-1]] = value
return attrs
def dump_bcache(bcache_sysfs_path, stats, print_subdevices, device):
'''Dump bcache stats'''
global devnum_map
def fmt_cachesize(val):
return '%s\t(%d%%)' % (format_sectors(val), 100.0 * val / cache_sectors)
attrs = [
(None, 'Device', lambda x: '%s (%s)' % (devnum_map.get(device, '?'), device)),
(None, 'UUID', lambda x: os.path.basename(bcache_sysfs_path)),
('block_size', 'Block Size', pretty_size),
('bucket_size', 'Bucket Size', pretty_size),
('congested', 'Congested?', str_to_bool),
('congested_read_threshold_us', 'Read Congestion', lambda x: '%.1fms' % (int(x) / 1000)),
('congested_write_threshold_us', 'Write Congestion', lambda x: '%.1fms' % (int(x) / 1000)),
(None, 'Total Cache Size', lambda x: format_sectors(cache_sectors)),
(None, 'Total Cache Used', lambda x: fmt_cachesize(cache_used_sectors)),
(None, 'Total Cache Unused', lambda x: fmt_cachesize(cache_unused_sectors)),
('dirty_data', 'Dirty Data', lambda x: fmt_cachesize(interpret_sectors(x))),
('cache_available_percent', 'Evictable Cache', lambda x: '%s\t(%s%%)' % (format_sectors(float(x) * cache_sectors / 100), x)),
(None, 'Replacement Policy', lambda x: replacement_policies.pop() if len(replacement_policies) == 1 else '(Unknown)'),
(None, 'Cache Mode', lambda x: cache_modes.pop() if len(cache_modes) == 1 else '(Unknown)'),
]
# Calculate aggregate data
cache_sectors = 0
cache_unused_sectors = 0
cache_modes = set()
replacement_policies = set()
for obj in os.listdir(bcache_sysfs_path):
if not os.path.isdir('%s/%s' % (bcache_sysfs_path, obj)):
continue
if obj.startswith('cache'):
cache_size = int(file_to_line('%s/%s/../size' % (bcache_sysfs_path, obj)))
cache_sectors += cache_size
cstats = get_cache_priority_stats('%s/%s' % (bcache_sysfs_path, obj))
unused_size = float(cstats['Unused'][:-1]) * cache_size / 100
cache_unused_sectors += unused_size
replacement_policies.add(file_to_line('%s/%s/cache_replacement_policy' % (bcache_sysfs_path, obj)))
elif obj.startswith('bdev'):
cache_modes.add(file_to_line('%s/%s/cache_mode' % (bcache_sysfs_path, obj)))
cache_used_sectors = cache_sectors - cache_unused_sectors
# Dump basic stats
print("--- bcache ---")
for (sysfs_name, display_name, conversion_func) in attrs:
if sysfs_name is not None:
val = file_to_line('%s/%s' % (bcache_sysfs_path, sysfs_name))
else:
val = None
if conversion_func is not None:
val = conversion_func(val)
if display_name is None:
display_name = sysfs_name
print('%-*s%s' % (MAX_KEY_LENGTH, display_name, val))
dump_stats(bcache_sysfs_path, '', stats)
# Dump sub-device stats
if not print_subdevices:
return
for obj in os.listdir(bcache_sysfs_path):
if not os.path.isdir('%s/%s' % (bcache_sysfs_path, obj)):
continue
if obj.startswith('bdev'):
dump_bdev('%s/%s' % (bcache_sysfs_path, obj))
dump_stats('%s/%s' % (bcache_sysfs_path, obj), ' ', stats)
elif obj.startswith('cache'):
dump_cachedev('%s/%s' % (bcache_sysfs_path, obj))
def map_uuid_to_device():
'''Map bcache UUIDs to device files.'''
global SYSFS_BLOCK_PATH
ret = {}
for bdev in os.listdir(SYSFS_BLOCK_PATH):
link = '%s%s/bcache/cache' % (SYSFS_BLOCK_PATH, bdev)
if not os.path.islink(link):
continue
basename = os.path.basename(os.readlink(link))
ret[basename] = file_to_line('%s%s/dev' % (SYSFS_BLOCK_PATH, bdev))
return ret
def map_devnum_to_device():
'''Map device numbers to device files.'''
global DEV_BLOCK_PATH
ret = {}
for bdev in os.listdir(DEV_BLOCK_PATH):
ret[bdev] = os.path.realpath('%s%s' % (DEV_BLOCK_PATH, bdev))
return ret
def print_help():
print('Usage: %s [OPTIONS]' % sys.argv[0])
print('Options:')
print(' -f Print the last five minutes of stats.')
print(' -d Print the last hour of stats.')
print(' -h Print the last day of stats.')
print(' -t Print total stats.')
print(' -a Print all stats.')
print(' -r Reset stats after printing them.')
print(' -s Print subdevice status.')
print(' -g Invoke GC before printing status.')
print('By default, print only the total stats.')
def main():
'''Main function'''
global SYSFS_BCACHE_PATH
global uuid_map, devnum_map
stats = set()
reset_stats = False
print_subdevices = False
run_gc = False
for arg in sys.argv[1:]:
if arg == '--help':
print_help()
return 0
elif arg == '-f':
stats.add('five_minute')
elif arg == '-h':
stats.add('hour')
elif arg == '-d':
stats.add('day')
elif arg == '-t':
stats.add('total')
elif arg == '-a':
stats.add('five_minute')
stats.add('hour')
stats.add('day')
stats.add('total')
elif arg == '-r':
reset_stats = True
elif arg == '-s':
print_subdevices = True
elif arg == '-g':
run_gc = True
else:
print_help()
return 0
if len(stats) == 0:
stats.add('total')
uuid_map = map_uuid_to_device()
devnum_map = map_devnum_to_device()
for cache in os.listdir(SYSFS_BCACHE_PATH):
if not os.path.isdir('%s%s' % (SYSFS_BCACHE_PATH, cache)):
continue
if run_gc:
with open('%s%s/internal/trigger_gc' % (SYSFS_BCACHE_PATH, cache), 'w') as fd:
fd.write('1\n')
dump_bcache('%s%s' % (SYSFS_BCACHE_PATH, cache), stats, print_subdevices, uuid_map.get(cache, '?'))
if reset_stats:
with open('%s%s/clear_stats' % (SYSFS_BCACHE_PATH, cache), 'w') as fd:
fd.write('1\n')
SYSFS_BCACHE_PATH = '/sys/fs/bcache/'
SYSFS_BLOCK_PATH = '/sys/block/'
DEV_BLOCK_PATH = '/dev/block/'
if __name__ == '__main__':
main()
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