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Name	Size	Permission	Date
lib	[ DIR ]	drwxr-xr-x	2025-11-05 21:34
argdist_example.txt	22.49 KB	-rw-r--r--	2023-12-08 15:36
bashreadline_example.txt	882 B	-rw-r--r--	2023-12-08 15:36
bindsnoop_example.txt	4.42 KB	-rw-r--r--	2023-12-08 15:36
biolatency_example.txt	23.46 KB	-rw-r--r--	2023-12-08 15:36
biolatpcts_example.txt	2.97 KB	-rw-r--r--	2023-12-08 15:36
biopattern_example.txt	1.37 KB	-rw-r--r--	2023-12-08 15:36
biosnoop_example.txt	3.47 KB	-rw-r--r--	2023-12-08 15:36
biotop_example.txt	9.11 KB	-rw-r--r--	2023-12-08 15:36
bitesize_example.txt	4.98 KB	-rw-r--r--	2023-12-08 15:36
bpflist_example.txt	2.13 KB	-rw-r--r--	2023-12-08 15:36
btrfsdist_example.txt	9.32 KB	-rw-r--r--	2023-12-08 15:36
btrfsslower_example.txt	6.65 KB	-rw-r--r--	2023-12-08 15:36
cachestat_example.txt	3.92 KB	-rw-r--r--	2023-12-08 15:36
cachetop_example.txt	3.83 KB	-rw-r--r--	2023-12-08 15:36
capable_example.txt	6.5 KB	-rw-r--r--	2023-12-08 15:36
cobjnew_example.txt	2.97 KB	-rw-r--r--	2023-12-08 15:36
compactsnoop_example.txt	9.92 KB	-rw-r--r--	2023-12-08 15:36
cpudist_example.txt	16.48 KB	-rw-r--r--	2023-12-08 15:36
cpuunclaimed_example.txt	15.2 KB	-rw-r--r--	2023-12-08 15:36
criticalstat_example.txt	4.81 KB	-rw-r--r--	2023-12-08 15:36
cthreads_example.txt	2.08 KB	-rw-r--r--	2023-12-08 15:36
dbslower_example.txt	3.89 KB	-rw-r--r--	2023-12-08 15:36
dbstat_example.txt	6.5 KB	-rw-r--r--	2023-12-08 15:36
dcsnoop_example.txt	4.27 KB	-rw-r--r--	2023-12-08 15:36
dcstat_example.txt	3.26 KB	-rw-r--r--	2023-12-08 15:36
deadlock_example.txt	16.25 KB	-rw-r--r--	2023-12-08 15:36
dirtop_example.txt	4.98 KB	-rw-r--r--	2023-12-08 15:36
drsnoop_example.txt	5 KB	-rw-r--r--	2023-12-08 15:36
execsnoop_example.txt	6.64 KB	-rw-r--r--	2023-12-08 15:36
exitsnoop_example.txt	6.22 KB	-rw-r--r--	2023-12-08 15:36
ext4dist_example.txt	8.78 KB	-rw-r--r--	2023-12-08 15:36
ext4slower_example.txt	11.07 KB	-rw-r--r--	2023-12-08 15:36
filegone_example.txt	743 B	-rw-r--r--	2023-12-08 15:36
filelife_example.txt	2.04 KB	-rw-r--r--	2023-12-08 15:36
fileslower_example.txt	5.58 KB	-rw-r--r--	2023-12-08 15:36
filetop_example.txt	6.8 KB	-rw-r--r--	2023-12-08 15:36
funccount_example.txt	13.29 KB	-rw-r--r--	2023-12-08 15:36
funcinterval_example.txt	15.28 KB	-rw-r--r--	2023-12-08 15:36
funclatency_example.txt	20.98 KB	-rw-r--r--	2023-12-08 15:36
funcslower_example.txt	6.63 KB	-rw-r--r--	2023-12-08 15:36
gethostlatency_example.txt	1.29 KB	-rw-r--r--	2023-12-08 15:36
hardirqs_example.txt	37.05 KB	-rw-r--r--	2023-12-08 15:36
inject_example.txt	6.67 KB	-rw-r--r--	2023-12-08 15:36
javacalls_example.txt	3.91 KB	-rw-r--r--	2023-12-08 15:36
javaflow_example.txt	5.88 KB	-rw-r--r--	2023-12-08 15:36
javagc_example.txt	3.78 KB	-rw-r--r--	2023-12-08 15:36
javaobjnew_example.txt	2.97 KB	-rw-r--r--	2023-12-08 15:36
javastat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
javathreads_example.txt	2.08 KB	-rw-r--r--	2023-12-08 15:36
killsnoop_example.txt	1.31 KB	-rw-r--r--	2023-12-08 15:36
klockstat_example.txt	8.34 KB	-rw-r--r--	2023-12-08 15:36
kvmexit_example.txt	11.63 KB	-rw-r--r--	2023-12-08 15:36
llcstat_example.txt	3.24 KB	-rw-r--r--	2023-12-08 15:36
mdflush_example.txt	1.74 KB	-rw-r--r--	2023-12-08 15:36
memleak_example.txt	10.02 KB	-rw-r--r--	2023-12-08 15:36
mountsnoop_example.txt	1.45 KB	-rw-r--r--	2023-12-08 15:36
mysqld_qslower_example.txt	2.3 KB	-rw-r--r--	2023-12-08 15:36
netqtop_example.txt	12.2 KB	-rw-r--r--	2023-12-08 15:36
nfsdist_example.txt	8.31 KB	-rw-r--r--	2023-12-08 15:36
nfsslower_example.txt	7.68 KB	-rw-r--r--	2023-12-08 15:36
nodegc_example.txt	3.78 KB	-rw-r--r--	2023-12-08 15:36
nodestat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
offcputime_example.txt	19.2 KB	-rw-r--r--	2023-12-08 15:36
offwaketime_example.txt	37.36 KB	-rw-r--r--	2023-12-08 15:36
oomkill_example.txt	1.88 KB	-rw-r--r--	2023-12-08 15:36
opensnoop_example.txt	10.33 KB	-rw-r--r--	2023-12-08 15:36
perlcalls_example.txt	3.91 KB	-rw-r--r--	2023-12-08 15:36
perlflow_example.txt	5.88 KB	-rw-r--r--	2023-12-08 15:36
perlstat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
phpcalls_example.txt	3.91 KB	-rw-r--r--	2023-12-08 15:36
phpflow_example.txt	5.88 KB	-rw-r--r--	2023-12-08 15:36
phpstat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
pidpersec_example.txt	677 B	-rw-r--r--	2023-12-08 15:36
ppchcalls_example.txt	6.93 KB	-rw-r--r--	2023-12-08 15:36
profile_example.txt	31.08 KB	-rw-r--r--	2023-12-08 15:36
pythoncalls_example.txt	3.91 KB	-rw-r--r--	2023-12-08 15:36
pythonflow_example.txt	5.88 KB	-rw-r--r--	2023-12-08 15:36
pythongc_example.txt	3.78 KB	-rw-r--r--	2023-12-08 15:36
pythonstat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
rdmaucma_example.txt	1.94 KB	-rw-r--r--	2023-12-08 15:36
readahead_example.txt	3.17 KB	-rw-r--r--	2023-12-08 15:36
reset-trace_example.txt	9.15 KB	-rw-r--r--	2023-12-08 15:36
rubycalls_example.txt	3.91 KB	-rw-r--r--	2023-12-08 15:36
rubyflow_example.txt	5.88 KB	-rw-r--r--	2023-12-08 15:36
rubygc_example.txt	3.78 KB	-rw-r--r--	2023-12-08 15:36
rubyobjnew_example.txt	2.97 KB	-rw-r--r--	2023-12-08 15:36
rubystat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
runqlat_example.txt	31.3 KB	-rw-r--r--	2023-12-08 15:36
runqlen_example.txt	11.85 KB	-rw-r--r--	2023-12-08 15:36
runqslower_example.txt	2.13 KB	-rw-r--r--	2023-12-08 15:36
shmsnoop_example.txt	2.73 KB	-rw-r--r--	2023-12-08 15:36
slabratetop_example.txt	5.22 KB	-rw-r--r--	2023-12-08 15:36
sofdsnoop_example.txt	3.14 KB	-rw-r--r--	2023-12-08 15:36
softirqs_example.txt	11.02 KB	-rw-r--r--	2023-12-08 15:36
solisten_example.txt	2.3 KB	-rw-r--r--	2023-12-08 15:36
sslsniff_example.txt	6.74 KB	-rw-r--r--	2023-12-08 15:36
stackcount_example.txt	21.45 KB	-rw-r--r--	2023-12-08 15:36
statsnoop_example.txt	3.02 KB	-rw-r--r--	2023-12-08 15:36
swapin.txt	2.57 KB	-rw-r--r--	2023-12-08 15:36
swapin_example.txt	1.39 KB	-rw-r--r--	2023-12-08 15:36
syncsnoop_example.txt	387 B	-rw-r--r--	2023-12-08 15:36
syscount_example.txt	6.27 KB	-rw-r--r--	2023-12-08 15:36
tclcalls_example.txt	3.91 KB	-rw-r--r--	2023-12-08 15:36
tclflow_example.txt	5.88 KB	-rw-r--r--	2023-12-08 15:36
tclobjnew_example.txt	2.97 KB	-rw-r--r--	2023-12-08 15:36
tclstat_example.txt	2.98 KB	-rw-r--r--	2023-12-08 15:36
tcpaccept_example.txt	2.76 KB	-rw-r--r--	2023-12-08 15:36
tcpcong_example.txt	33.31 KB	-rw-r--r--	2023-12-08 15:36
tcpconnect_example.txt	6.27 KB	-rw-r--r--	2023-12-08 15:36
tcpconnlat_example.txt	2.55 KB	-rw-r--r--	2023-12-08 15:36
tcpdrop_example.txt	1.95 KB	-rw-r--r--	2023-12-08 15:36
tcplife_example.txt	6.83 KB	-rw-r--r--	2023-12-08 15:36
tcpretrans_example.txt	3.85 KB	-rw-r--r--	2023-12-08 15:36
tcprtt_example.txt	9.83 KB	-rw-r--r--	2023-12-08 15:36
tcpstates_example.txt	2.84 KB	-rw-r--r--	2023-12-08 15:36
tcpsubnet_example.txt	5.37 KB	-rw-r--r--	2023-12-08 15:36
tcpsynbl_example.txt	1.15 KB	-rw-r--r--	2023-12-08 15:36
tcptop_example.txt	5.75 KB	-rw-r--r--	2023-12-08 15:36
tcptracer_example.txt	1.98 KB	-rw-r--r--	2023-12-08 15:36
threadsnoop_example.txt	1.07 KB	-rw-r--r--	2023-12-08 15:36
tplist_example.txt	4.4 KB	-rw-r--r--	2023-12-08 15:36
trace_example.txt	21.62 KB	-rw-r--r--	2023-12-08 15:36
ttysnoop_example.txt	3.24 KB	-rw-r--r--	2023-12-08 15:36
vfscount_example.txt	2.17 KB	-rw-r--r--	2023-12-08 15:36
vfsstat_example.txt	1.66 KB	-rw-r--r--	2023-12-08 15:36
virtiostat_example.txt	2.62 KB	-rw-r--r--	2023-12-08 15:36
wakeuptime_example.txt	33.25 KB	-rw-r--r--	2023-12-08 15:36
xfsdist_example.txt	6.77 KB	-rw-r--r--	2023-12-08 15:36
xfsslower_example.txt	6.91 KB	-rw-r--r--	2023-12-08 15:36
zfsdist_example.txt	9.52 KB	-rw-r--r--	2023-12-08 15:36
zfsslower_example.txt	7.37 KB	-rw-r--r--	2023-12-08 15:36

Rename

Demonstrations of dcstat, the Linux eBPF/bcc version.

dcstat shows directory entry cache (dcache) statistics. For example:

# ./dcstat 
TIME         REFS/s   SLOW/s   MISS/s     HIT%
08:11:47:      2059      141       97    95.29
08:11:48:     79974      151      106    99.87
08:11:49:    192874      146      102    99.95
08:11:50:      2051      144      100    95.12
08:11:51:     73373    17239    17194    76.57
08:11:52:     54685    25431    25387    53.58
08:11:53:     18127     8182     8137    55.12
08:11:54:     22517    10345    10301    54.25
08:11:55:      7524     2881     2836    62.31
08:11:56:      2067      141       97    95.31
08:11:57:      2115      145      101    95.22

The output shows the total references per second ("REFS/s"), the number that
took a slower code path to be processed ("SLOW/s"), the number of dcache misses
("MISS/s"), and the hit ratio as a percentage. By default, an interval of 1
second is used.

At 08:11:49, there were 192 thousand references, which almost entirely hit
from the dcache, with a hit ration of 99.95%. A little later, starting at
08:11:51, a workload began that walked many uncached files, reducing the hit
ratio to 53%, and more importantly, a miss rate of over 10 thousand per second.

Here's an interesting workload:

# ./dcstat 
TIME         REFS/s   SLOW/s   MISS/s     HIT%
08:15:53:    250683      141       97    99.96
08:15:54:    266115      145      101    99.96
08:15:55:    268428      141       97    99.96
08:15:56:    260389      143       99    99.96

It's a 99.96% hit ratio, and these are all negative hits: accessing a file that
does not exist. Here's the C program that generated the workload:

# cat -n badopen.c
     1	#include <sys/types.h>
     2	#include <sys/stat.h>
     3	#include <fcntl.h>
     4	
     5	int
     6	main(int argc, char *argv[])
     7	{
     8	    int fd;
     9	    while (1) {
    10	        fd = open("bad", O_RDONLY);
    11	    }
    12	    return 0;
    13	}

This is a simple workload generator than tries to open a missing file ("bad")
as quickly as possible.

Lets see what happens if the workload attempts to open a different filename
each time (which is also a missing file), using the following C code:

# cat -n badopen2.c
     1	#include <sys/types.h>
     2	#include <sys/stat.h>
     3	#include <fcntl.h>
     4	#include <stdio.h>
     5	
     6	int
     7	main(int argc, char *argv[])
     8	{
     9	    int fd, i = 0;
    10	    char buf[128] = {};
    11	
    12	    while (1) {
    13	        sprintf(buf, "bad%d", i++);
    14	        fd = open(buf, O_RDONLY);
    15	    }
    16	    return 0;
    17	}

Here's dcstat:

# ./dcstat 
TIME         REFS/s   SLOW/s   MISS/s     HIT%
08:18:52:    241131   237544   237505     1.51
08:18:53:    238210   236323   236278     0.82
08:18:54:    235259   233307   233261     0.85
08:18:55:    233144   231256   231214     0.83
08:18:56:    231981   230097   230053     0.83

dcstat also supports an optional interval and optional count. For example,
printing 5 second summaries 3 times:

# ./dcstat 5 3
TIME         REFS/s   SLOW/s   MISS/s     HIT%
08:20:03:      2085      143       99    95.23
08:20:08:      2077      143       98    95.24
08:20:14:      2071      144      100    95.15

USAGE message:

# ./dcstat -h
USAGE: ./dcstat [interval [count]]