- tools/[biotop](tools/biotop.py): Top for disks: Summarize block device I/O by process. [Examples](tools/biotop_example.txt).
- tools/[biosnoop](tools/biosnoop.py): Trace block device I/O with PID and latency. [Examples](tools/biosnoop_example.txt).
- tools/[bitesize](tools/bitesize.py): Show per process I/O size histogram. [Examples](tools/bitesize_example.txt).
+- tools/[btrfsslower](tools/btrfsslower.py): Trace slow btrfs operations. [Examples](tools/btrfsslower_example.txt).
- tools/[cachestat](tools/cachestat.py): Trace page cache hit/miss ratio. [Examples](tools/cachestat_example.txt).
- tools/[dcsnoop](tools/dcsnoop.py): Trace directory entry cache (dcache) lookups. [Examples](tools/dcsnoop_example.txt).
- tools/[dcstat](tools/dcstat.py): Directory entry cache (dcache) stats. [Examples](tools/dcstat_example.txt).
--- /dev/null
+.TH btrfsslower 8 "2016-02-15" "USER COMMANDS"
+.SH NAME
+btrfsslower \- Trace slow btrfs file operations, with per-event details.
+.SH SYNOPSIS
+.B btrfsslower [\-h] [\-j] [\-p PID] [min_ms]
+.SH DESCRIPTION
+This tool traces common btrfs file operations: reads, writes, opens, and
+syncs. It measures the time spent in these operations, and prints details
+for each that exceeded a threshold.
+
+WARNING: See the OVERHEAD section.
+
+By default, a minimum millisecond threshold of 10 is used. If a threshold of 0
+is used, all events are printed (warning: verbose).
+
+Since this works by tracing the btrfs_file_operations interface functions, it
+will need updating to match any changes to these functions.
+
+Since this uses BPF, only the root user can use this tool.
+.SH REQUIREMENTS
+CONFIG_BPF and bcc.
+.SH OPTIONS
+\-p PID
+Trace this PID only.
+.TP
+min_ms
+Minimum I/O latency (duration) to trace, in milliseconds. Default is 10 ms.
+.SH EXAMPLES
+.TP
+Trace synchronous file reads and writes slower than 10 ms:
+#
+.B btrfsslower
+.TP
+Trace slower than 1 ms:
+#
+.B btrfsslower 1
+.TP
+Trace slower than 1 ms, and output just the fields in parsable format (csv):
+#
+.B btrfsslower \-j 1
+.TP
+Trace all file reads and writes (warning: the output will be verbose):
+#
+.B btrfsslower 0
+.TP
+Trace slower than 1 ms, for PID 181 only:
+#
+.B btrfsslower \-p 181 1
+.SH FIELDS
+.TP
+TIME(s)
+Time of I/O completion since the first I/O seen, in seconds.
+.TP
+COMM
+Process name.
+.TP
+PID
+Process ID.
+.TP
+T
+Type of operation. R == read, W == write, O == open, S == fsync.
+.TP
+OFF_KB
+File offset for the I/O, in Kbytes.
+.TP
+BYTES
+Size of I/O, in bytes.
+.TP
+LAT(ms)
+Latency (duration) of I/O, measured from when it was issued by VFS to the
+filesystem, to when it completed. This time is inclusive of block device I/O,
+file system CPU cycles, file system locks, run queue latency, etc. It's a more
+accurate measure of the latency suffered by applications performing file
+system I/O, than to measure this down at the block device interface.
+.TP
+FILENAME
+A cached kernel file name (comes from dentry->d_iname).
+.TP
+ENDTIME_us
+Completion timestamp, microseconds (\-j only).
+.TP
+OFFSET_b
+File offset, bytes (\-j only).
+.TP
+LATENCY_us
+Latency (duration) of the I/O, in microseconds (\-j only).
+.SH OVERHEAD
+This adds low-overhead instrumentation to btrfs writes and fsyncs, as well
+as all system reads and opens (due to the current implementation of the
+btrfs_file_operations interface). Particularly, all reads and writes from
+the file system cache will incur extra overhead while tracing. Such reads and
+writes can be very frequent (depending on the workload; eg, 1M/sec), at which
+point the overhead of this tool may become noticeable.
+Measure and quantify before use. If this
+continues to be a problem, consider switching to a tool that prints in-kernel
+summaries only, such as btrfsdist(8).
+.PP
+Note that the overhead of this tool should be less than fileslower(8), as
+this tool targets btrfs functions only, and not all file read/write paths
+(which can include socket I/O).
+.SH SOURCE
+This is from bcc.
+.IP
+https://github.com/iovisor/bcc
+.PP
+Also look in the bcc distribution for a companion _examples.txt file containing
+example usage, output, and commentary for this tool.
+.SH OS
+Linux
+.SH STABILITY
+Unstable - in development.
+.SH AUTHOR
+Brendan Gregg
+.SH SEE ALSO
+btrfsdist(8), biosnoop(8), funccount(8), fileslower(8)
--- /dev/null
+#!/usr/bin/python
+# @lint-avoid-python-3-compatibility-imports
+#
+# btrfsslower Trace slow btrfs operations.
+# For Linux, uses BCC, eBPF.
+#
+# USAGE: btrfsslower [-h] [-j] [-p PID] [min_ms]
+#
+# This script traces common btrfs file operations: reads, writes, opens, and
+# syncs. It measures the time spent in these operations, and prints details
+# for each that exceeded a threshold.
+#
+# WARNING: This adds low-overhead instrumentation to these btrfs operations,
+# including reads and writes from the file system cache. Such reads and writes
+# can be very frequent (depending on the workload; eg, 1M/sec), at which
+# point the overhead of this tool (even if it prints no "slower" events) can
+# begin to become significant.
+#
+# By default, a minimum millisecond threshold of 10 is used.
+#
+# Copyright 2016 Netflix, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License")
+#
+# 15-Feb-2016 Brendan Gregg Created this.
+
+from __future__ import print_function
+from bcc import BPF
+import argparse
+from time import strftime
+import ctypes as ct
+
+# symbols
+kallsyms = "/proc/kallsyms"
+
+# arguments
+examples = """examples:
+ ./btrfsslower # trace operations slower than 10 ms (default)
+ ./btrfsslower 1 # trace operations slower than 1 ms
+ ./btrfsslower -j 1 # ... 1 ms, parsable output (csv)
+ ./btrfsslower 0 # trace all operations (warning: verbose)
+ ./btrfsslower -p 185 # trace PID 185 only
+"""
+parser = argparse.ArgumentParser(
+ description="Trace common btrfs file operations slower than a threshold",
+ formatter_class=argparse.RawDescriptionHelpFormatter,
+ epilog=examples)
+parser.add_argument("-j", "--csv", action="store_true",
+ help="just print fields: comma-separated values")
+parser.add_argument("-p", "--pid",
+ help="trace this PID only")
+parser.add_argument("min_ms", nargs="?", default='10',
+ help="minimum I/O duration to trace, in ms (default 10)")
+args = parser.parse_args()
+min_ms = int(args.min_ms)
+pid = args.pid
+csv = args.csv
+debug = 0
+
+# define BPF program
+bpf_text = """
+#include <uapi/linux/ptrace.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/dcache.h>
+
+// XXX: switch these to char's when supported
+#define TRACE_READ 0
+#define TRACE_WRITE 1
+#define TRACE_OPEN 2
+#define TRACE_FSYNC 3
+
+struct val_t {
+ u64 ts;
+ u64 offset;
+ struct file *fp;
+};
+
+struct data_t {
+ // XXX: switch some to u32's when supported
+ u64 ts_us;
+ u64 type;
+ u64 size;
+ u64 offset;
+ u64 delta_us;
+ u64 pid;
+ char task[TASK_COMM_LEN];
+ char file[DNAME_INLINE_LEN];
+};
+
+BPF_HASH(entryinfo, pid_t, struct val_t);
+BPF_PERF_OUTPUT(events);
+
+//
+// Store timestamp and size on entry
+//
+
+// The current btrfs (Linux 4.5) uses generic_file_read_iter() instead of it's
+// own read function. So we need to trace that and then filter on btrfs, which
+// I do by checking file->f_op.
+int trace_read_entry(struct pt_regs *ctx, struct kiocb *iocb)
+{
+ u32 pid;
+ pid = bpf_get_current_pid_tgid();
+ if (FILTER_PID)
+ return 0;
+
+ // btrfs filter on file->f_op == btrfs_file_operations
+ struct file *fp = iocb->ki_filp;
+ if ((u64)fp->f_op != BTRFS_FILE_OPERATIONS)
+ return 0;
+
+ // store filep and timestamp by pid
+ struct val_t val = {};
+ val.ts = bpf_ktime_get_ns();
+ val.fp = fp;
+ val.offset = iocb->ki_pos;
+ if (val.fp)
+ entryinfo.update(&pid, &val);
+
+ return 0;
+}
+
+// btrfs_file_write_iter():
+int trace_write_entry(struct pt_regs *ctx, struct kiocb *iocb)
+{
+ u32 pid;
+ pid = bpf_get_current_pid_tgid();
+ if (FILTER_PID)
+ return 0;
+
+ // store filep and timestamp by pid
+ struct val_t val = {};
+ val.ts = bpf_ktime_get_ns();
+ val.fp = iocb->ki_filp;
+ val.offset = iocb->ki_pos;
+ if (val.fp)
+ entryinfo.update(&pid, &val);
+
+ return 0;
+}
+
+// The current btrfs (Linux 4.5) uses generic_file_open(), instead of it's own
+// function. Same as with reads. Trace the generic path and filter:
+int trace_open_entry(struct pt_regs *ctx, struct inode *inode,
+ struct file *file)
+{
+ u32 pid;
+ pid = bpf_get_current_pid_tgid();
+ if (FILTER_PID)
+ return 0;
+
+ // btrfs filter on file->f_op == btrfs_file_operations
+ if ((u64)file->f_op != BTRFS_FILE_OPERATIONS)
+ return 0;
+
+ // store filep and timestamp by pid
+ struct val_t val = {};
+ val.ts = bpf_ktime_get_ns();
+ val.fp = file;
+ val.offset = 0;
+ if (val.fp)
+ entryinfo.update(&pid, &val);
+
+ return 0;
+}
+
+// btrfs_sync_file():
+int trace_fsync_entry(struct pt_regs *ctx, struct file *file)
+{
+ u32 pid;
+ pid = bpf_get_current_pid_tgid();
+ if (FILTER_PID)
+ return 0;
+
+ // store filep and timestamp by pid
+ struct val_t val = {};
+ val.ts = bpf_ktime_get_ns();
+ val.fp = file;
+ val.offset = 0;
+ if (val.fp)
+ entryinfo.update(&pid, &val);
+
+ return 0;
+}
+
+//
+// Output
+//
+
+static int trace_return(struct pt_regs *ctx, int type)
+{
+ struct val_t *valp;
+ u32 pid = bpf_get_current_pid_tgid();
+
+ valp = entryinfo.lookup(&pid);
+ if (valp == 0) {
+ // missed tracing issue or filtered
+ return 0;
+ }
+
+ // calculate delta
+ u64 ts = bpf_ktime_get_ns();
+ u64 delta_us = (ts - valp->ts) / 1000;
+ entryinfo.delete(&pid);
+ if (FILTER_US)
+ return 0;
+
+ // workaround (rewriter should handle file to d_iname in one step):
+ struct dentry *de = NULL;
+ bpf_probe_read(&de, sizeof(de), &valp->fp->f_path.dentry);
+
+ // populate output struct
+ u32 size = ctx->ax;
+ struct data_t data = {.type = type, .size = size, .delta_us = delta_us,
+ .pid = pid};
+ data.ts_us = ts / 1000;
+ data.offset = valp->offset;
+ bpf_probe_read(&data.file, sizeof(data.file), de->d_iname);
+ bpf_get_current_comm(&data.task, sizeof(data.task));
+
+ events.perf_submit(ctx, &data, sizeof(data));
+
+ return 0;
+}
+
+int trace_read_return(struct pt_regs *ctx)
+{
+ return trace_return(ctx, TRACE_READ);
+}
+
+int trace_write_return(struct pt_regs *ctx)
+{
+ return trace_return(ctx, TRACE_WRITE);
+}
+
+int trace_open_return(struct pt_regs *ctx)
+{
+ return trace_return(ctx, TRACE_OPEN);
+}
+
+int trace_fsync_return(struct pt_regs *ctx)
+{
+ return trace_return(ctx, TRACE_FSYNC);
+}
+
+"""
+
+# code replacements
+with open(kallsyms) as syms:
+ ops = ''
+ for line in syms:
+ a = line.rstrip().split()
+ (addr, name) = (a[0], a[2])
+ if name == "btrfs_file_operations":
+ ops = "0x" + addr
+ break
+ if ops == '':
+ print("ERROR: no btrfs_file_operations in /proc/kallsyms. Exiting.")
+ exit()
+ bpf_text = bpf_text.replace('BTRFS_FILE_OPERATIONS', ops)
+if min_ms == 0:
+ bpf_text = bpf_text.replace('FILTER_US', '0')
+else:
+ bpf_text = bpf_text.replace('FILTER_US',
+ 'delta_us <= %s' % str(min_ms * 1000))
+if args.pid:
+ bpf_text = bpf_text.replace('FILTER_PID', 'pid != %s' % pid)
+else:
+ bpf_text = bpf_text.replace('FILTER_PID', '0')
+if debug:
+ print(bpf_text)
+
+# kernel->user event data: struct data_t
+DNAME_INLINE_LEN = 32 # linux/dcache.h
+TASK_COMM_LEN = 16 # linux/sched.h
+class Data(ct.Structure):
+ _fields_ = [
+ ("ts_us", ct.c_ulonglong),
+ ("type", ct.c_ulonglong),
+ ("size", ct.c_ulonglong),
+ ("offset", ct.c_ulonglong),
+ ("delta_us", ct.c_ulonglong),
+ ("pid", ct.c_ulonglong),
+ ("task", ct.c_char * TASK_COMM_LEN),
+ ("file", ct.c_char * DNAME_INLINE_LEN)
+ ]
+
+# process event
+def print_event(cpu, data, size):
+ event = ct.cast(data, ct.POINTER(Data)).contents
+
+ type = 'R'
+ if event.type == 1:
+ type = 'W'
+ elif event.type == 2:
+ type = 'O'
+ elif event.type == 3:
+ type = 'S'
+
+ if (csv):
+ print("%d,%s,%d,%s,%d,%d,%d,%s" % (
+ event.ts_us, event.task, event.pid, type, event.size,
+ event.offset, event.delta_us, event.file))
+ return
+ print("%-8s %-14.14s %-6s %1s %-7s %-8d %7.2f %s" % (strftime("%H:%M:%S"),
+ event.task, event.pid, type, event.size, event.offset / 1024,
+ float(event.delta_us) / 1000, event.file))
+
+# initialize BPF
+b = BPF(text=bpf_text)
+
+# Common file functions. See earlier comment about generic_*().
+b.attach_kprobe(event="generic_file_read_iter", fn_name="trace_read_entry")
+b.attach_kprobe(event="btrfs_file_write_iter", fn_name="trace_write_entry")
+b.attach_kprobe(event="generic_file_open", fn_name="trace_open_entry")
+b.attach_kprobe(event="btrfs_sync_file", fn_name="trace_fsync_entry")
+b.attach_kretprobe(event="generic_file_read_iter", fn_name="trace_read_return")
+b.attach_kretprobe(event="btrfs_file_write_iter", fn_name="trace_write_return")
+b.attach_kretprobe(event="generic_file_open", fn_name="trace_open_return")
+b.attach_kretprobe(event="btrfs_sync_file", fn_name="trace_fsync_return")
+
+# header
+if (csv):
+ print("ENDTIME_us,TASK,PID,TYPE,BYTES,OFFSET_b,LATENCY_us,FILE")
+else:
+ if min_ms == 0:
+ print("Tracing btrfs operations")
+ else:
+ print("Tracing btrfs operations slower than %d ms" % min_ms)
+ print("%-8s %-14s %-6s %1s %-7s %-8s %7s %s" % ("TIME", "COMM", "PID", "T",
+ "BYTES", "OFF_KB", "LAT(ms)", "FILENAME"))
+
+# read events
+b["events"].open_perf_buffer(print_event)
+while 1:
+ b.kprobe_poll()
--- /dev/null
+Demonstrations of btrfsslower, the Linux eBPF/bcc version.
+
+
+btrfsslower shows btrfs reads, writes, opens, and fsyncs, slower than a
+threshold. For example:
+
+# ./btrfsslower
+Tracing btrfs operations slower than 10 ms
+TIME COMM PID T BYTES OFF_KB LAT(ms) FILENAME
+01:22:03 randread.pl 13602 R 8192 391384 10.40 data1
+01:22:03 randread.pl 13602 R 8192 92632 10.41 data1
+01:22:06 randread.pl 13602 R 8192 199800 17.33 data1
+01:22:06 randread.pl 13602 R 8192 415160 17.21 data1
+01:22:07 randread.pl 13602 R 8192 729984 11.93 data1
+01:22:09 randread.pl 13602 R 8192 342784 11.90 data1
+[...]
+
+This shows several reads from a "randread.pl" program, each 8 Kbytes in size,
+and from a "data1" file. These all had over 10 ms latency.
+
+This "latency" is measured from when the operation was issued from the VFS
+interface to the file system, to when it completed. This spans everything:
+block device I/O (disk I/O), file system CPU cycles, file system locks, run
+queue latency, etc. This is a better measure of the latency suffered by
+applications reading from the file system than measuring this down at the
+block device interface.
+
+Note that this only traces the common file system operations previously
+listed: other file system operations (eg, inode operations including
+getattr()) are not traced.
+
+
+The threshold can be provided as an argument. Eg, I/O slower than 1 ms:
+
+# ./btrfsslower 1
+Tracing btrfs operations slower than 1 ms
+TIME COMM PID T BYTES OFF_KB LAT(ms) FILENAME
+03:26:54 randread.pl 30578 R 8192 214864 1.87 data1
+03:26:54 randread.pl 30578 R 8192 267600 1.48 data1
+03:26:54 randread.pl 30578 R 8192 704200 1.30 data1
+03:26:54 randread.pl 30578 R 8192 492352 3.09 data1
+03:26:55 randread.pl 30578 R 8192 319448 1.34 data1
+03:26:55 randread.pl 30578 R 8192 676032 1.88 data1
+03:26:55 randread.pl 30578 R 8192 646712 2.24 data1
+03:26:55 randread.pl 30578 R 8192 124376 1.02 data1
+03:26:55 randread.pl 30578 R 8192 223064 2.64 data1
+03:26:55 randread.pl 30578 R 8192 521280 1.55 data1
+03:26:55 randread.pl 30578 R 8192 272992 2.48 data1
+03:26:55 randread.pl 30578 R 8192 450112 2.67 data1
+03:26:55 randread.pl 30578 R 8192 361808 1.78 data1
+03:26:55 randread.pl 30578 R 8192 41088 1.46 data1
+03:26:55 randread.pl 30578 R 8192 756576 1.67 data1
+03:26:55 randread.pl 30578 R 8192 711776 2.74 data1
+03:26:55 randread.pl 30578 R 8192 129472 1.34 data1
+03:26:55 randread.pl 30578 R 8192 526928 1.82 data1
+03:26:56 randread.pl 30578 R 8192 312768 1.44 data1
+03:26:56 randread.pl 30578 R 8192 34720 1.14 data1
+03:26:56 randread.pl 30578 R 8192 258376 1.13 data1
+03:26:56 randread.pl 30578 R 8192 308456 1.44 data1
+03:26:56 randread.pl 30578 R 8192 759656 1.27 data1
+03:26:56 randread.pl 30578 R 8192 387424 3.24 data1
+03:26:56 randread.pl 30578 R 8192 168864 3.38 data1
+03:26:56 randread.pl 30578 R 8192 699296 1.38 data1
+03:26:56 randread.pl 30578 R 8192 405688 2.37 data1
+03:26:56 randread.pl 30578 R 8192 559064 1.18 data1
+03:26:56 randread.pl 30578 R 8192 264808 1.13 data1
+03:26:56 randread.pl 30578 R 8192 369240 2.20 data1
+[...]
+
+There's now much more output (this spans less than 3 seconds, the previous output
+spanned 6 seconds), as the lower threshold is catching more I/O.
+
+
+A threshold of 0 will trace all operations. Warning: the output will be
+verbose, as it will include all file system cache hits.
+
+# ./btrfsslower 0
+Tracing btrfs operations
+TIME COMM PID T BYTES OFF_KB LAT(ms) FILENAME
+03:28:17 bash 32597 O 0 0 0.00 date.txt
+03:28:17 date 32597 W 29 0 0.02 date.txt
+03:28:23 cksum 32743 O 0 0 0.00 date.txt
+03:28:23 cksum 32743 R 29 0 0.01 date.txt
+03:28:23 cksum 32743 R 0 0 0.00 date.txt
+
+While tracing, the following commands were run in another window:
+
+# date > date.txt
+# cksum date.txt
+
+The output of btrfsslower now includes open operations ("O"), and writes ("W").
+The first read from cksum(1) returned 29 bytes, and the second returned 0:
+causing cksum(1) to stop reading.
+
+
+A -j option will print just the fields (parsable output, csv):
+
+# ./btrfsslower -j 1
+ENDTIME_us,TASK,PID,TYPE,BYTES,OFFSET_b,LATENCY_us,FILE
+8930665366,randread.pl,2717,R,8192,230391808,4312,data1
+8930670746,randread.pl,2717,R,8192,347832320,1296,data1
+8930675995,randread.pl,2717,R,8192,409812992,4207,data1
+8930680213,randread.pl,2717,R,8192,498204672,3104,data1
+8930685970,randread.pl,2717,R,8192,553164800,1843,data1
+8930687568,randread.pl,2717,R,8192,339492864,1475,data1
+8930694108,randread.pl,2717,R,8192,500711424,6276,data1
+8930697139,randread.pl,2717,R,8192,485801984,2180,data1
+8930705755,randread.pl,2717,R,8192,376922112,7535,data1
+8930711340,randread.pl,2717,R,8192,380084224,3314,data1
+8930740964,randread.pl,2717,R,8192,226091008,24762,data1
+8930743169,randread.pl,2717,R,8192,361570304,1809,data1
+8930748789,randread.pl,2717,R,8192,346931200,1530,data1
+8930763514,randread.pl,2717,R,8192,59719680,13938,data1
+8930764870,randread.pl,2717,R,8192,406511616,1313,data1
+8930774327,randread.pl,2717,R,8192,661430272,7361,data1
+8930780360,randread.pl,2717,R,8192,406904832,2220,data1
+8930785736,randread.pl,2717,R,8192,523419648,2005,data1
+8930794560,randread.pl,2717,R,8192,342974464,8388,data1
+[...]
+
+This may be useful for visualizing with another tool, for example, for
+producing a scatter plot of ENDTIME vs LATENCY, to look for time-based
+patterns.
+
+
+USAGE message:
+
+# ./btrfsslower -h
+usage: btrfsslower [-h] [-j] [-p PID] [min_ms]
+
+Trace common btrfs file operations slower than a threshold
+
+positional arguments:
+ min_ms minimum I/O duration to trace, in ms (default 10)
+
+optional arguments:
+ -h, --help show this help message and exit
+ -j, --csv just print fields: comma-separated values
+ -p PID, --pid PID trace this PID only
+
+examples:
+ ./btrfsslower # trace operations slower than 10 ms (default)
+ ./btrfsslower 1 # trace operations slower than 1 ms
+ ./btrfsslower -j 1 # ... 1 ms, parsable output (csv)
+ ./btrfsslower 0 # trace all operations (warning: verbose)
+ ./btrfsslower -p 185 # trace PID 185 only
projects / platform / upstream / bcc.git / commitdiff