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Make 'tools/wakeuptime' use stack maps
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This modifies 'tools/wakeuptime' to use the stack maps feature.
Rather than using manual, depth-limited stack walking with some
architecture-specific code, using stack maps makes the script
usable across different architectures. This also adds command
line arguments to let the user to set the minimum and maximum
amount of time in microseconds over which traces are stored.

Signed-off-by: Sandipan Das <[email protected]>
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@sandip4n
sandip4n committed Nov 16, 2017
1 parent 0342ef5 commit 2c2d46f
Showing 1 changed file with 74 additions and 76 deletions.
150 changes: 74 additions & 76 deletions tools/wakeuptime.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,12 +5,6 @@
#
# USAGE: wakeuptime [-h] [-u] [-p PID] [-v] [-f] [duration]
#
# The current implementation uses an unrolled loop for x86_64, and was written
# as a proof of concept. This implementation should be replaced in the future
# with an appropriate bpf_ call, when available.
#
# Currently limited to a stack trace depth of 21 (maxdepth + 1).
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
Expand All @@ -21,6 +15,25 @@
from time import sleep, strftime
import argparse
import signal
import errno
from sys import stderr

# arg validation
def positive_int(val):
try:
ival = int(val)
except ValueError:
raise argparse.ArgumentTypeError("must be an integer")

if ival < 0:
raise argparse.ArgumentTypeError("must be positive")
return ival

def positive_nonzero_int(val):
ival = positive_int(val)
if ival == 0:
raise argparse.ArgumentTypeError("must be nonzero")
return ival

# arguments
examples = """examples:
Expand All @@ -37,21 +50,33 @@
parser.add_argument("-u", "--useronly", action="store_true",
help="user threads only (no kernel threads)")
parser.add_argument("-p", "--pid",
type=positive_int,
help="trace this PID only")
parser.add_argument("-v", "--verbose", action="store_true",
help="show raw addresses")
parser.add_argument("-f", "--folded", action="store_true",
help="output folded format")
parser.add_argument("--stack-storage-size", default=1024,
type=positive_nonzero_int,
help="the number of unique stack traces that can be stored and "
"displayed (default 1024)")
parser.add_argument("duration", nargs="?", default=99999999,
type=positive_nonzero_int,
help="duration of trace, in seconds")
parser.add_argument("-m", "--min-block-time", default=1,
type=positive_nonzero_int,
help="the amount of time in microseconds over which we " +
"store traces (default 1)")
parser.add_argument("-M", "--max-block-time", default=(1 << 64) - 1,
type=positive_nonzero_int,
help="the amount of time in microseconds under which we " +
"store traces (default U64_MAX)")
args = parser.parse_args()
folded = args.folded
duration = int(args.duration)
debug = 0
maxdepth = 20 # and MAXDEPTH
if args.pid and args.useronly:
print("ERROR: use either -p or -u.")
exit()
parser.error("use either -p or -u.")

# signal handler
def signal_ignore(signal, frame):
Expand All @@ -62,38 +87,17 @@ def signal_ignore(signal, frame):
#include <uapi/linux/ptrace.h>
#include <linux/sched.h>
#define MAXDEPTH 20
#define MINBLOCK_US 1
#define MINBLOCK_US MINBLOCK_US_VALUEULL
#define MAXBLOCK_US MAXBLOCK_US_VALUEULL
struct key_t {
int w_k_stack_id;
char waker[TASK_COMM_LEN];
char target[TASK_COMM_LEN];
// Skip saving the ip
u64 ret[MAXDEPTH];
};
BPF_HASH(counts, struct key_t);
BPF_HASH(start, u32);
static u64 get_frame(u64 *bp) {
if (*bp) {
// The following stack walker is x86_64/arm64 specific
u64 ret = 0;
if (bpf_probe_read(&ret, sizeof(ret), (void *)(*bp+8)))
return 0;
if (bpf_probe_read(bp, sizeof(*bp), (void *)*bp))
return 0;
#ifdef __x86_64__
if (ret < __START_KERNEL_map)
#elif __aarch64__
if (ret < VA_START)
#else
#error "Unsupported architecture for stack walker"
#endif
return 0;
return ret;
}
return 0;
}
BPF_STACK_TRACE(stack_traces, STACK_STORAGE_SIZE)
int offcpu(struct pt_regs *ctx) {
u32 pid = bpf_get_current_pid_tgid();
Expand All @@ -118,41 +122,16 @@ def signal_ignore(signal, frame):
// calculate delta time
delta = bpf_ktime_get_ns() - *tsp;
delta = delta / 1000;
if (delta < MINBLOCK_US)
if ((delta < MINBLOCK_US) || (delta > MAXBLOCK_US))
return 0;
struct key_t key = {};
u64 zero = 0, *val, bp = 0;
int depth = 0;
u64 zero = 0, *val;
key.w_k_stack_id = stack_traces.get_stackid(ctx, BPF_F_REUSE_STACKID);
bpf_probe_read(&key.target, sizeof(key.target), p->comm);
bpf_get_current_comm(&key.waker, sizeof(key.waker));
bp = PT_REGS_FP(ctx);
// unrolled loop (MAXDEPTH):
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
if (!(key.ret[depth++] = get_frame(&bp))) goto out;
out:
val = counts.lookup_or_init(&key, &zero);
(*val) += delta;
return 0;
Expand All @@ -165,6 +144,12 @@ def signal_ignore(signal, frame):
else:
filter = '0'
bpf_text = bpf_text.replace('FILTER', filter)

# set stack storage size
bpf_text = bpf_text.replace('STACK_STORAGE_SIZE', str(args.stack_storage_size))
bpf_text = bpf_text.replace('MINBLOCK_US_VALUE', str(args.min_block_time))
bpf_text = bpf_text.replace('MAXBLOCK_US_VALUE', str(args.max_block_time))

if debug:
print(bpf_text)

Expand Down Expand Up @@ -195,30 +180,43 @@ def signal_ignore(signal, frame):

if not folded:
print()
missing_stacks = 0
has_enomem = False
counts = b.get_table("counts")
stack_traces = b.get_table("stack_traces")
for k, v in sorted(counts.items(), key=lambda counts: counts[1].value):
# handle get_stackid errors
# check for an ENOMEM error
if k.w_k_stack_id == -errno.ENOMEM:
missing_stacks += 1
continue

waker_kernel_stack = [] if k.w_k_stack_id < 1 else \
reversed(list(stack_traces.walk(k.w_k_stack_id))[1:])

if folded:
# print folded stack output
line = k.waker.decode() + ";"
for i in reversed(range(0, maxdepth)):
if k.ret[i] == 0:
continue
line = line + b.ksym(k.ret[i])
if i != 0:
line = line + ";"
print("%s;%s %d" % (line, k.target.decode(), v.value))
line = \
[k.waker.decode()] + \
[b.ksym(addr)
for addr in reversed(list(waker_kernel_stack))] + \
[k.target.decode()]
print("%s %d" % (";".join(line), v.value))
else:
# print default multi-line stack output
print(" %-16s %s" % ("target:", k.target.decode()))
for i in range(0, maxdepth):
if k.ret[i] == 0:
break
print(" %-16x %s" % (k.ret[i],
b.ksym(k.ret[i])))
for addr in waker_kernel_stack:
print(" %-16x %s" % (addr, b.ksym(addr)))
print(" %-16s %s" % ("waker:", k.waker.decode()))
print(" %d\n" % v.value)
counts.clear()

if missing_stacks > 0:
enomem_str = " Consider increasing --stack-storage-size."
print("WARNING: %d stack traces could not be displayed.%s" %
(missing_stacks, enomem_str),
file=stderr)

if not folded:
print("Detaching...")
exit()

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