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softirqs: Migrate to kernel tracepoints instead of kprobes (iovisor#1091
) This commit migrates softirqs to use kernel tracepoints instead of kprobes. Because tracepoints only provide the vector number and not the function name, we use a conversion table, which is borrowed from kernel/softirq.c, to translate the vector number to a display name. This table is expected to be fairly stable. Notably, new names have not been added since approximately 2009, and the last rename (without adding or removing a name) was in 2014. Resolves iovisor#1031.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,146 @@ | ||
| #!/usr/bin/python | ||
| # @lint-avoid-python-3-compatibility-imports | ||
| # | ||
| # softirqs Summarize soft IRQ (interrupt) event time. | ||
| # For Linux, uses BCC, eBPF. | ||
| # | ||
| # USAGE: softirqs [-h] [-T] [-N] [-d] [interval] [count] | ||
| # | ||
| # Copyright (c) 2015 Brendan Gregg. | ||
| # Licensed under the Apache License, Version 2.0 (the "License") | ||
| # | ||
| # 20-Oct-2015 Brendan Gregg Created this. | ||
|
|
||
| from __future__ import print_function | ||
| from bcc import BPF | ||
| from time import sleep, strftime | ||
| import argparse | ||
|
|
||
| # arguments | ||
| examples = """examples: | ||
| ./softirqs # sum soft irq event time | ||
| ./softirqs -d # show soft irq event time as histograms | ||
| ./softirqs 1 10 # print 1 second summaries, 10 times | ||
| ./softirqs -NT 1 # 1s summaries, nanoseconds, and timestamps | ||
| """ | ||
| parser = argparse.ArgumentParser( | ||
| description="Summarize soft irq event time as histograms", | ||
| formatter_class=argparse.RawDescriptionHelpFormatter, | ||
| epilog=examples) | ||
| parser.add_argument("-T", "--timestamp", action="store_true", | ||
| help="include timestamp on output") | ||
| parser.add_argument("-N", "--nanoseconds", action="store_true", | ||
| help="output in nanoseconds") | ||
| parser.add_argument("-d", "--dist", action="store_true", | ||
| help="show distributions as histograms") | ||
| parser.add_argument("interval", nargs="?", default=99999999, | ||
| help="output interval, in seconds") | ||
| parser.add_argument("count", nargs="?", default=99999999, | ||
| help="number of outputs") | ||
| args = parser.parse_args() | ||
| countdown = int(args.count) | ||
| if args.nanoseconds: | ||
| factor = 1 | ||
| label = "nsecs" | ||
| else: | ||
| factor = 1000 | ||
| label = "usecs" | ||
| debug = 0 | ||
|
|
||
| # define BPF program | ||
| bpf_text = """ | ||
| #include <uapi/linux/ptrace.h> | ||
| typedef struct irq_key { | ||
| u64 ip; | ||
| u64 slot; | ||
| } irq_key_t; | ||
| BPF_HASH(start, u32); | ||
| BPF_HASH(iptr, u32); | ||
| BPF_HISTOGRAM(dist, irq_key_t); | ||
| // time IRQ | ||
| int trace_start(struct pt_regs *ctx) | ||
| { | ||
| u32 pid = bpf_get_current_pid_tgid(); | ||
| u64 ip = PT_REGS_IP(ctx), ts = bpf_ktime_get_ns(); | ||
| start.update(&pid, &ts); | ||
| iptr.update(&pid, &ip); | ||
| return 0; | ||
| } | ||
| int trace_completion(struct pt_regs *ctx) | ||
| { | ||
| u64 *tsp, delta, ip, *ipp; | ||
| u32 pid = bpf_get_current_pid_tgid(); | ||
| // fetch timestamp and calculate delta | ||
| tsp = start.lookup(&pid); | ||
| ipp = iptr.lookup(&pid); | ||
| if (tsp == 0 || ipp == 0) { | ||
| return 0; // missed start | ||
| } | ||
| delta = bpf_ktime_get_ns() - *tsp; | ||
| ip = *ipp; | ||
| // store as sum or histogram | ||
| STORE | ||
| start.delete(&pid); | ||
| iptr.delete(&pid); | ||
| return 0; | ||
| } | ||
| """ | ||
|
|
||
| # code substitutions | ||
| if args.dist: | ||
| bpf_text = bpf_text.replace('STORE', | ||
| 'irq_key_t key = {.ip = ip, .slot = bpf_log2l(delta)};' + | ||
| 'dist.increment(key);') | ||
| else: | ||
| bpf_text = bpf_text.replace('STORE', | ||
| 'irq_key_t key = {.ip = ip, .slot = 0 /* ignore */};' + | ||
| 'u64 zero = 0, *vp = dist.lookup_or_init(&key, &zero);' + | ||
| '(*vp) += delta;') | ||
| if debug: | ||
| print(bpf_text) | ||
|
|
||
| # load BPF program | ||
| b = BPF(text=bpf_text) | ||
|
|
||
| # this should really use irq:softirq_entry/exit tracepoints; for now the | ||
| # soft irq functions are individually traced (search your kernel for | ||
| # open_softirq() calls, and adjust the following list as needed). | ||
| for softirqfunc in ("blk_iopoll_softirq", "blk_done_softirq", | ||
| "rcu_process_callbacks", "run_rebalance_domains", "tasklet_action", | ||
| "tasklet_hi_action", "run_timer_softirq", "net_tx_action", | ||
| "net_rx_action"): | ||
| b.attach_kprobe(event=softirqfunc, fn_name="trace_start") | ||
| b.attach_kretprobe(event=softirqfunc, fn_name="trace_completion") | ||
|
|
||
| print("Tracing soft irq event time... Hit Ctrl-C to end.") | ||
|
|
||
| # output | ||
| exiting = 0 if args.interval else 1 | ||
| dist = b.get_table("dist") | ||
| while (1): | ||
| try: | ||
| sleep(int(args.interval)) | ||
| except KeyboardInterrupt: | ||
| exiting = 1 | ||
|
|
||
| print() | ||
| if args.timestamp: | ||
| print("%-8s\n" % strftime("%H:%M:%S"), end="") | ||
|
|
||
| if args.dist: | ||
| dist.print_log2_hist(label, "softirq", section_print_fn=b.ksym) | ||
| else: | ||
| print("%-26s %11s" % ("SOFTIRQ", "TOTAL_" + label)) | ||
| for k, v in sorted(dist.items(), key=lambda dist: dist[1].value): | ||
| print("%-26s %11d" % (b.ksym(k.ip), v.value / factor)) | ||
| dist.clear() | ||
|
|
||
| countdown -= 1 | ||
| if exiting or countdown == 0: | ||
| exit() |
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