Merge pull request iovisor#627 from brendangregg/master

merge most .c and .py examples

README.md

@@ -38,10 +38,9 @@ Tracing... Hit Ctrl-C to end.
 The above output shows a bimodal distribution, where the largest mode of
 800 I/O was between 128 and 255 Kbytes in size.
 
-See the source: [bitehist.c](examples/tracing/bitehist.c) and
-[bitehist.py](examples/tracing/bitehist.py). What this traces, what this stores, and how
-the data is presented, can be entirely customized. This shows only some of
-many possible capabilities.
+See the source: [bitehist.py](examples/tracing/bitehist.py). What this traces,
+what this stores, and how the data is presented, can be entirely customized.
+This shows only some of many possible capabilities.
 
 ## Installing
 
@@ -60,9 +59,11 @@ pair of .c and .py files, and some are directories of files.
 
 Examples:
 
-- examples/tracing/[bitehist.py](examples/tracing/bitehist.py) examples/tracing/[bitehist.c](examples/tracing/bitehist.c): Block I/O size histogram. [Examples](examples/tracing/bitehist_example.txt).
-- examples/tracing/[disksnoop.py](examples/tracing/disksnoop.py) examples/tracing/[disksnoop.c](examples/tracing/disksnoop.c): Trace block device I/O latency. [Examples](examples/tracing/disksnoop_example.txt).
+- examples/tracing/[bitehist.py](examples/tracing/bitehist.py): Block I/O size histogram. [Examples](examples/tracing/bitehist_example.txt).
+- examples/tracing/[disksnoop.py](examples/tracing/disksnoop.py): Trace block device I/O latency. [Examples](examples/tracing/disksnoop_example.txt).
 - examples/[hello_world.py](examples/hello_world.py): Prints "Hello, World!" for new processes.
+- examples/tracing/[nodejs_http_server.py](examples/tracing/nodejs_http_server.py): Trace Node.js HTTP server requests using USDT probes.
+- examples/tracing/[task_switch.py](examples/tracing/task_switch.py): Count task switches with from and to PIDs.
 - examples/tracing/[tcpv4connect.py](examples/tracing/tcpv4connect.py): Trace TCP IPv4 active connections. [Examples](examples/tracing/tcpv4connect_example.txt).
 - examples/tracing/[trace_fields.py](examples/tracing/trace_fields.py): Simple example of printing fields from traced events.
 - examples/tracing/[urandomread.py](examples/tracing/urandomread.py): A kernel tracepoint example, which traces random:urandom_read. [Examples](examples/tracing/urandomread_example.txt).
@@ -188,7 +189,7 @@ The BPF program always takes at least one argument, which is a pointer to the
 context for this type of program. Different program types have different calling
 conventions, but for this one we don't care so `void *` is fine.
 ```python
-BPF(text='void kprobe__sys_clone(void *ctx) { bpf_trace_printk("Hello, World!\\n"); }').trace_print()
+BPF(text='int kprobe__sys_clone(void *ctx) { bpf_trace_printk("Hello, World!\\n"); return 0; }').trace_print()
 ```
 
 For this example, we will call the program every time `fork()` is called by a

examples/hello_world.py

@@ -8,4 +8,4 @@
 
 from bcc import BPF
 
-BPF(text='void kprobe__sys_clone(void *ctx) { bpf_trace_printk("Hello, World!\\n"); }').trace_print()
+BPF(text='int kprobe__sys_clone(void *ctx) { bpf_trace_printk("Hello, World!\\n"); return 0; }').trace_print()

examples/tracing/bitehist.py

@@ -1,7 +1,7 @@
 #!/usr/bin/python
 #
 # bitehist.py Block I/O size histogram.
-# For Linux, uses BCC, eBPF. See .c file.
+# For Linux, uses BCC, eBPF. Embedded C.
 #
 # Written as a basic example of using a histogram to show a distribution.
 #
@@ -17,7 +17,18 @@
 from time import sleep
 
 # load BPF program
-b = BPF(src_file = "bitehist.c")
+b = BPF(text="""
+#include <uapi/linux/ptrace.h>
+#include <linux/blkdev.h>
+
+BPF_HISTOGRAM(dist);
+
+int kprobe__blk_account_io_completion(struct pt_regs *ctx, struct request *req)
+{
+ dist.increment(bpf_log2l(req->__data_len / 1024));
+ return 0;
+}
+""")
 
 # header
 print("Tracing... Hit Ctrl-C to end.")

examples/tracing/disksnoop.py

@@ -1,7 +1,7 @@
 #!/usr/bin/python
 #
 # disksnoop.py Trace block device I/O: basic version of iosnoop.
-# For Linux, uses BCC, eBPF. See .c file.
+# For Linux, uses BCC, eBPF. Embedded C.
 #
 # Written as a basic example of tracing latency.
 #
@@ -16,7 +16,32 @@
 REQ_WRITE = 1 # from include/linux/blk_types.h
 
 # load BPF program
-b = BPF(src_file="disksnoop.c")
+b = BPF(text="""
+#include <uapi/linux/ptrace.h>
+#include <linux/blkdev.h>
+
+BPF_HASH(start, struct request *);
+
+void trace_start(struct pt_regs *ctx, struct request *req) {
+ // stash start timestamp by request ptr
+ u64 ts = bpf_ktime_get_ns();
+
+ start.update(&req, &ts);
+}
+
+void trace_completion(struct pt_regs *ctx, struct request *req) {
+ u64 *tsp, delta;
+
+ tsp = start.lookup(&req);
+ if (tsp != 0) {
+ delta = bpf_ktime_get_ns() - *tsp;
+ bpf_trace_printk("%d %x %d\\n", req->__data_len,
+ req->cmd_flags, delta / 1000);
+ start.delete(&req);
+ }
+}
+""")
+
 b.attach_kprobe(event="blk_start_request", fn_name="trace_start")
 b.attach_kprobe(event="blk_mq_start_request", fn_name="trace_start")
 b.attach_kprobe(event="blk_account_io_completion", fn_name="trace_completion")

examples/tracing/task_switch.py

@@ -5,7 +5,28 @@
 from bcc import BPF
 from time import sleep
 
-b = BPF(src_file="task_switch.c")
+b = BPF(text="""
+#include <uapi/linux/ptrace.h>
+#include <linux/sched.h>
+
+struct key_t {
+ u32 prev_pid;
+ u32 curr_pid;
+};
+// map_type, key_type, leaf_type, table_name, num_entry
+BPF_TABLE("hash", struct key_t, u64, stats, 1024);
+int count_sched(struct pt_regs *ctx, struct task_struct *prev) {
+ struct key_t key = {};
+ u64 zero = 0, *val;
+
+ key.curr_pid = bpf_get_current_pid_tgid();
+ key.prev_pid = prev->pid;
+
+ val = stats.lookup_or_init(&key, &zero);
+ (*val)++;
+ return 0;
+}
+""")
 b.attach_kprobe(event="finish_task_switch", fn_name="count_sched")
 
 # generate many schedule events