1 2# BPF Compiler Collection (BCC) 3 4BCC is a toolkit for creating efficient kernel tracing and manipulation 5programs, and includes several useful tools and examples. It makes use of 6extended BPF (Berkeley Packet Filters), formally known as eBPF, a new feature 7that was first added to Linux 3.15. Much of what BCC uses requires Linux 4.1 8and above. 9 10eBPF was [described by](https://lkml.org/lkml/2015/4/14/232) Ingo Molnár as: 11 12> One of the more interesting features in this cycle is the ability to attach eBPF programs (user-defined, sandboxed bytecode executed by the kernel) to kprobes. This allows user-defined instrumentation on a live kernel image that can never crash, hang or interfere with the kernel negatively. 13 14BCC makes BPF programs easier to write, with kernel instrumentation in C 15(and includes a C wrapper around LLVM), and front-ends in Python and lua. 16It is suited for many tasks, including performance analysis and network 17traffic control. 18 19## Screenshot 20 21This example traces a disk I/O kernel function, and populates an in-kernel 22power-of-2 histogram of the I/O size. For efficiency, only the histogram 23summary is returned to user-level. 24 25```Shell 26# ./bitehist.py 27Tracing... Hit Ctrl-C to end. 28^C 29 kbytes : count distribution 30 0 -> 1 : 3 | | 31 2 -> 3 : 0 | | 32 4 -> 7 : 211 |********** | 33 8 -> 15 : 0 | | 34 16 -> 31 : 0 | | 35 32 -> 63 : 0 | | 36 64 -> 127 : 1 | | 37 128 -> 255 : 800 |**************************************| 38``` 39 40The above output shows a bimodal distribution, where the largest mode of 41800 I/O was between 128 and 255 Kbytes in size. 42 43See the source: [bitehist.py](examples/tracing/bitehist.py). What this traces, 44what this stores, and how the data is presented, can be entirely customized. 45This shows only some of many possible capabilities. 46 47## Installing 48 49See [INSTALL.md](INSTALL.md) for installation steps on your platform. 50 51## FAQ 52 53See [FAQ.txt](FAQ.txt) for the most common troubleshoot questions. 54 55## Reference guide 56 57See [docs/reference_guide.md](docs/reference_guide.md) for the reference guide to the bcc and bcc/BPF APIs. 58 59## Contents 60 61Some of these are single files that contain both C and Python, others have a 62pair of .c and .py files, and some are directories of files. 63 64### Tracing 65 66#### Examples: 67 68- examples/tracing/[bitehist.py](examples/tracing/bitehist.py): Block I/O size histogram. [Examples](examples/tracing/bitehist_example.txt). 69- examples/tracing/[disksnoop.py](examples/tracing/disksnoop.py): Trace block device I/O latency. [Examples](examples/tracing/disksnoop_example.txt). 70- examples/[hello_world.py](examples/hello_world.py): Prints "Hello, World!" for new processes. 71- examples/tracing/[mysqld_query.py](examples/tracing/mysqld_query.py): Trace MySQL server queries using USDT probes. [Examples](examples/tracing/mysqld_query_example.txt). 72- examples/tracing/[nodejs_http_server.py](examples/tracing/nodejs_http_server.py): Trace Node.js HTTP server requests using USDT probes. [Examples](examples/tracing/nodejs_http_server_example.txt). 73- examples/tracing/[stacksnoop](examples/tracing/stacksnoop.py): Trace a kernel function and print all kernel stack traces. [Examples](examples/tracing/stacksnoop_example.txt). 74- tools/[statsnoop](tools/statsnoop.py): Trace stat() syscalls. [Examples](tools/statsnoop_example.txt). 75- examples/tracing/[task_switch.py](examples/tracing/task_switch.py): Count task switches with from and to PIDs. 76- examples/tracing/[tcpv4connect.py](examples/tracing/tcpv4connect.py): Trace TCP IPv4 active connections. [Examples](examples/tracing/tcpv4connect_example.txt). 77- examples/tracing/[trace_fields.py](examples/tracing/trace_fields.py): Simple example of printing fields from traced events. 78- examples/tracing/[urandomread.py](examples/tracing/urandomread.py): A kernel tracepoint example, which traces random:urandom_read. [Examples](examples/tracing/urandomread_example.txt). 79- examples/tracing/[vfsreadlat.py](examples/tracing/vfsreadlat.py) examples/tracing/[vfsreadlat.c](examples/tracing/vfsreadlat.c): VFS read latency distribution. [Examples](examples/tracing/vfsreadlat_example.txt). 80- examples/tracing/[kvm_hypercall.py](examples/tracing/kvm_hypercall.py): Conditional static kernel tracepoints for KVM entry, exit and hypercall [Examples](examples/tracing/kvm_hypercall.txt). 81 82#### Tools: 83<center><a href="images/bcc_tracing_tools_2017.png"><img src="images/bcc_tracing_tools_2017.png" border=0 width=700></a></center> 84 85 86- tools/[argdist](tools/argdist.py): Display function parameter values as a histogram or frequency count. [Examples](tools/argdist_example.txt). 87- tools/[bashreadline](tools/bashreadline.py): Print entered bash commands system wide. [Examples](tools/bashreadline_example.txt). 88- tools/[biolatency](tools/biolatency.py): Summarize block device I/O latency as a histogram. [Examples](tools/biolatency_example.txt). 89- tools/[biotop](tools/biotop.py): Top for disks: Summarize block device I/O by process. [Examples](tools/biotop_example.txt). 90- tools/[biosnoop](tools/biosnoop.py): Trace block device I/O with PID and latency. [Examples](tools/biosnoop_example.txt). 91- tools/[bitesize](tools/bitesize.py): Show per process I/O size histogram. [Examples](tools/bitesize_example.txt). 92- tools/[bpflist](tools/bpflist.py): Display processes with active BPF programs and maps. [Examples](tools/bpflist_example.txt). 93- tools/[btrfsdist](tools/btrfsdist.py): Summarize btrfs operation latency distribution as a histogram. [Examples](tools/btrfsdist_example.txt). 94- tools/[btrfsslower](tools/btrfsslower.py): Trace slow btrfs operations. [Examples](tools/btrfsslower_example.txt). 95- tools/[capable](tools/capable.py): Trace security capability checks. [Examples](tools/capable_example.txt). 96- tools/[cachestat](tools/cachestat.py): Trace page cache hit/miss ratio. [Examples](tools/cachestat_example.txt). 97- tools/[cachetop](tools/cachetop.py): Trace page cache hit/miss ratio by processes. [Examples](tools/cachetop_example.txt). 98- tools/[cpudist](tools/cpudist.py): Summarize on- and off-CPU time per task as a histogram. [Examples](tools/cpudist_example.txt) 99- tools/[cpuunclaimed](tools/cpuunclaimed.py): Sample CPU run queues and calculate unclaimed idle CPU. [Examples](tools/cpuunclaimed_example.txt) 100- tools/[criticalstat](tools/criticalstat.py): Trace and report long atomic critical sections in the kernel. [Examples](tools/criticalstat_example.txt) 101- tools/[dbslower](tools/dbslower.py): Trace MySQL/PostgreSQL queries slower than a threshold. [Examples](tools/dbslower_example.txt). 102- tools/[dbstat](tools/dbstat.py): Summarize MySQL/PostgreSQL query latency as a histogram. [Examples](tools/dbstat_example.txt). 103- tools/[dcsnoop](tools/dcsnoop.py): Trace directory entry cache (dcache) lookups. [Examples](tools/dcsnoop_example.txt). 104- tools/[dcstat](tools/dcstat.py): Directory entry cache (dcache) stats. [Examples](tools/dcstat_example.txt). 105- tools/[deadlock_detector](tools/deadlock_detector.py): Detect potential deadlocks on a running process. [Examples](tools/deadlock_detector_example.txt). 106- tools/[execsnoop](tools/execsnoop.py): Trace new processes via exec() syscalls. [Examples](tools/execsnoop_example.txt). 107- tools/[ext4dist](tools/ext4dist.py): Summarize ext4 operation latency distribution as a histogram. [Examples](tools/ext4dist_example.txt). 108- tools/[ext4slower](tools/ext4slower.py): Trace slow ext4 operations. [Examples](tools/ext4slower_example.txt). 109- tools/[filelife](tools/filelife.py): Trace the lifespan of short-lived files. [Examples](tools/filelife_example.txt). 110- tools/[fileslower](tools/fileslower.py): Trace slow synchronous file reads and writes. [Examples](tools/fileslower_example.txt). 111- tools/[filetop](tools/filetop.py): File reads and writes by filename and process. Top for files. [Examples](tools/filetop_example.txt). 112- tools/[funccount](tools/funccount.py): Count kernel function calls. [Examples](tools/funccount_example.txt). 113- tools/[funclatency](tools/funclatency.py): Time functions and show their latency distribution. [Examples](tools/funclatency_example.txt). 114- tools/[funcslower](tools/funcslower.py): Trace slow kernel or user function calls. [Examples](tools/funcslower_example.txt). 115- tools/[gethostlatency](tools/gethostlatency.py): Show latency for getaddrinfo/gethostbyname[2] calls. [Examples](tools/gethostlatency_example.txt). 116- tools/[hardirqs](tools/hardirqs.py): Measure hard IRQ (hard interrupt) event time. [Examples](tools/hardirqs_example.txt). 117- tools/[inject](tools/inject.py): Targeted error injection with call chain and predicates [Examples](tools/inject_example.txt). 118- tools/[killsnoop](tools/killsnoop.py): Trace signals issued by the kill() syscall. [Examples](tools/killsnoop_example.txt). 119- tools/[llcstat](tools/llcstat.py): Summarize CPU cache references and misses by process. [Examples](tools/llcstat_example.txt). 120- tools/[mdflush](tools/mdflush.py): Trace md flush events. [Examples](tools/mdflush_example.txt). 121- tools/[mysqld_qslower](tools/mysqld_qslower.py): Trace MySQL server queries slower than a threshold. [Examples](tools/mysqld_qslower_example.txt). 122- tools/[memleak](tools/memleak.py): Display outstanding memory allocations to find memory leaks. [Examples](tools/memleak_example.txt). 123- tools/[nfsslower](tools/nfsslower.py): Trace slow NFS operations. [Examples](tools/nfsslower_example.txt). 124- tools/[nfsdist](tools/nfsdist.py): Summarize NFS operation latency distribution as a histogram. [Examples](tools/nfsdist_example.txt). 125- tools/[offcputime](tools/offcputime.py): Summarize off-CPU time by kernel stack trace. [Examples](tools/offcputime_example.txt). 126- tools/[offwaketime](tools/offwaketime.py): Summarize blocked time by kernel off-CPU stack and waker stack. [Examples](tools/offwaketime_example.txt). 127- tools/[oomkill](tools/oomkill.py): Trace the out-of-memory (OOM) killer. [Examples](tools/oomkill_example.txt). 128- tools/[opensnoop](tools/opensnoop.py): Trace open() syscalls. [Examples](tools/opensnoop_example.txt). 129- tools/[pidpersec](tools/pidpersec.py): Count new processes (via fork). [Examples](tools/pidpersec_example.txt). 130- tools/[profile](tools/profile.py): Profile CPU usage by sampling stack traces at a timed interval. [Examples](tools/profile_example.txt). 131- tools/[reset-trace](tools/reset-trace.sh): Reset the state of tracing. Maintenance tool only. [Examples](tools/reset-trace_example.txt). 132- tools/[runqlat](tools/runqlat.py): Run queue (scheduler) latency as a histogram. [Examples](tools/runqlat_example.txt). 133- tools/[runqlen](tools/runqlen.py): Run queue length as a histogram. [Examples](tools/runqlen_example.txt). 134- tools/[runqslower](tools/runqslower.py): Trace long process scheduling delays. [Examples](tools/runqslower_example.txt). 135- tools/[slabratetop](tools/slabratetop.py): Kernel SLAB/SLUB memory cache allocation rate top. [Examples](tools/slabratetop_example.txt). 136- tools/[softirqs](tools/softirqs.py): Measure soft IRQ (soft interrupt) event time. [Examples](tools/softirqs_example.txt). 137- tools/[solisten](tools/solisten.py): Trace TCP socket listen. [Examples](tools/solisten_example.txt). 138- tools/[sslsniff](tools/sslsniff.py): Sniff OpenSSL written and readed data. [Examples](tools/sslsniff_example.txt). 139- tools/[stackcount](tools/stackcount.py): Count kernel function calls and their stack traces. [Examples](tools/stackcount_example.txt). 140- tools/[syncsnoop](tools/syncsnoop.py): Trace sync() syscall. [Examples](tools/syncsnoop_example.txt). 141- tools/[syscount](tools/syscount.py): Summarize syscall counts and latencies. [Examples](tools/syscount_example.txt). 142- tools/[tcpaccept](tools/tcpaccept.py): Trace TCP passive connections (accept()). [Examples](tools/tcpaccept_example.txt). 143- tools/[tcpconnect](tools/tcpconnect.py): Trace TCP active connections (connect()). [Examples](tools/tcpconnect_example.txt). 144- tools/[tcpconnlat](tools/tcpconnlat.py): Trace TCP active connection latency (connect()). [Examples](tools/tcpconnlat_example.txt). 145- tools/[tcpdrop](tools/tcpdrop.py): Trace kernel-based TCP packet drops with details. [Examples](tools/tcpdrop_example.txt). 146- tools/[tcplife](tools/tcplife.py): Trace TCP sessions and summarize lifespan. [Examples](tools/tcplife_example.txt). 147- tools/[tcpretrans](tools/tcpretrans.py): Trace TCP retransmits and TLPs. [Examples](tools/tcpretrans_example.txt). 148- tools/[tcpstates](tools/tcpstates.py): Trace TCP session state changes with durations. [Examples](tools/tcpstates_example.txt). 149- tools/[tcpsubnet](tools/tcpsubnet.py): Summarize and aggregate TCP send by subnet. [Examples](tools/tcpsubnet_example.txt). 150- tools/[tcptop](tools/tcptop.py): Summarize TCP send/recv throughput by host. Top for TCP. [Examples](tools/tcptop_example.txt). 151- tools/[tcptracer](tools/tcptracer.py): Trace TCP established connections (connect(), accept(), close()). [Examples](tools/tcptracer_example.txt). 152- tools/[tplist](tools/tplist.py): Display kernel tracepoints or USDT probes and their formats. [Examples](tools/tplist_example.txt). 153- tools/[trace](tools/trace.py): Trace arbitrary functions, with filters. [Examples](tools/trace_example.txt). 154- tools/[ttysnoop](tools/ttysnoop.py): Watch live output from a tty or pts device. [Examples](tools/ttysnoop_example.txt). 155- tools/[ucalls](tools/lib/ucalls.py): Summarize method calls or Linux syscalls in high-level languages. [Examples](tools/lib/ucalls_example.txt). 156- tools/[uflow](tools/lib/uflow.py): Print a method flow graph in high-level languages. [Examples](tools/lib/uflow_example.txt). 157- tools/[ugc](tools/lib/ugc.py): Trace garbage collection events in high-level languages. [Examples](tools/lib/ugc_example.txt). 158- tools/[uobjnew](tools/lib/uobjnew.py): Summarize object allocation events by object type and number of bytes allocated. [Examples](tools/lib/uobjnew_example.txt). 159- tools/[ustat](tools/lib/ustat.py): Collect events such as GCs, thread creations, object allocations, exceptions and more in high-level languages. [Examples](tools/lib/ustat_example.txt). 160- tools/[uthreads](tools/lib/uthreads.py): Trace thread creation events in Java and raw pthreads. [Examples](tools/lib/uthreads_example.txt). 161- tools/[vfscount](tools/vfscount.py) tools/[vfscount.c](tools/vfscount.c): Count VFS calls. [Examples](tools/vfscount_example.txt). 162- tools/[vfsstat](tools/vfsstat.py) tools/[vfsstat.c](tools/vfsstat.c): Count some VFS calls, with column output. [Examples](tools/vfsstat_example.txt). 163- tools/[wakeuptime](tools/wakeuptime.py): Summarize sleep to wakeup time by waker kernel stack. [Examples](tools/wakeuptime_example.txt). 164- tools/[xfsdist](tools/xfsdist.py): Summarize XFS operation latency distribution as a histogram. [Examples](tools/xfsdist_example.txt). 165- tools/[xfsslower](tools/xfsslower.py): Trace slow XFS operations. [Examples](tools/xfsslower_example.txt). 166- tools/[zfsdist](tools/zfsdist.py): Summarize ZFS operation latency distribution as a histogram. [Examples](tools/zfsdist_example.txt). 167- tools/[zfsslower](tools/zfsslower.py): Trace slow ZFS operations. [Examples](tools/zfsslower_example.txt). 168 169### Networking 170 171Examples: 172 173- examples/networking/[distributed_bridge/](examples/networking/distributed_bridge): Distributed bridge example. 174- examples/networking/[http_filter/](examples/networking/http_filter): Simple HTTP filter example. 175- examples/networking/[simple_tc.py](examples/networking/simple_tc.py): Simple traffic control example. 176- examples/networking/[simulation.py](examples/networking/simulation.py): Simulation helper. 177- examples/networking/neighbor_sharing/[tc_neighbor_sharing.py](examples/networking/neighbor_sharing/tc_neighbor_sharing.py) examples/networking/neighbor_sharing/[tc_neighbor_sharing.c](examples/networking/neighbor_sharing/tc_neighbor_sharing.c): Per-IP classification and rate limiting. 178- examples/networking/[tunnel_monitor/](examples/networking/tunnel_monitor): Efficiently monitor traffic flows. [Example video](https://www.youtube.com/watch?v=yYy3Cwce02k). 179- examples/networking/vlan_learning/[vlan_learning.py](examples/networking/vlan_learning/vlan_learning.py) examples/[vlan_learning.c](examples/networking/vlan_learning/vlan_learning.c): Demux Ethernet traffic into worker veth+namespaces. 180 181### BPF Introspection: 182 183Tools that help to introspect BPF programs. 184 185- introspection/[bps.c](introspection/bps.c): List all BPF programs loaded into the kernel. 'ps' for BPF programs. [Examples](introspection/bps_example.txt). 186 187## Motivation 188 189BPF guarantees that the programs loaded into the kernel cannot crash, and 190cannot run forever, but yet BPF is general purpose enough to perform many 191arbitrary types of computation. Currently, it is possible to write a program in 192C that will compile into a valid BPF program, yet it is vastly easier to 193write a C program that will compile into invalid BPF (C is like that). The user 194won't know until trying to run the program whether it was valid or not. 195 196With a BPF-specific frontend, one should be able to write in a language and 197receive feedback from the compiler on the validity as it pertains to a BPF 198backend. This toolkit aims to provide a frontend that can only create valid BPF 199programs while still harnessing its full flexibility. 200 201Furthermore, current integrations with BPF have a kludgy workflow, sometimes 202involving compiling directly in a linux kernel source tree. This toolchain aims 203to minimize the time that a developer spends getting BPF compiled, and instead 204focus on the applications that can be written and the problems that can be 205solved with BPF. 206 207The features of this toolkit include: 208* End-to-end BPF workflow in a shared library 209 * A modified C language for BPF backends 210 * Integration with llvm-bpf backend for JIT 211 * Dynamic (un)loading of JITed programs 212 * Support for BPF kernel hooks: socket filters, tc classifiers, 213 tc actions, and kprobes 214* Bindings for Python 215* Examples for socket filters, tc classifiers, and kprobes 216* Self-contained tools for tracing a running system 217 218In the future, more bindings besides python will likely be supported. Feel free 219to add support for the language of your choice and send a pull request! 220 221## Tutorials 222 223- [docs/tutorial.md](docs/tutorial.md): Using bcc tools to solve performance, troubleshooting, and networking issues. 224- [docs/tutorial_bcc_python_developer.md](docs/tutorial_bcc_python_developer.md): Developing new bcc programs using the Python interface. 225 226### Networking 227 228At Red Hat Summit 2015, BCC was presented as part of a [session on BPF](http://www.devnation.org/#7784f1f7513e8542e4db519e79ff5eec). 229A multi-host vxlan environment is simulated and a BPF program used to monitor 230one of the physical interfaces. The BPF program keeps statistics on the inner 231and outer IP addresses traversing the interface, and the userspace component 232turns those statistics into a graph showing the traffic distribution at 233multiple granularities. See the code [here](examples/networking/tunnel_monitor). 234 235[](https://youtu.be/yYy3Cwce02k) 236 237## Contributing 238 239Already pumped up to commit some code? Here are some resources to join the 240discussions in the [IOVisor](https://www.iovisor.org/) community and see 241what you want to work on. 242 243* _Mailing List:_ http://lists.iovisor.org/mailman/listinfo/iovisor-dev 244* _IRC:_ #iovisor at irc.oftc.net 245* _BCC Issue Tracker:_ [Github Issues](https://github.com/iovisor/bcc/issues) 246* _A guide for contributing scripts:_ [CONTRIBUTING-SCRIPTS.md](CONTRIBUTING-SCRIPTS.md) 247 248## External links 249 250Looking for more information on BCC and how it's being used? You can find links to other BCC content on the web in [LINKS.md](LINKS.md). 251
){kind=link}