ruby-allocator-count.py

#!/usr/bin/python
# to try this you'll need to edit in the name of your ruby binary and install bcc-tools
# bcc installation instructions are at https://github.com/iovisor/bcc/blob/master/INSTALL.md

from __future__ import print_function
from bcc import BPF
from time import sleep
import os

# load BPF program
b = BPF(text="""
#include <uapi/linux/ptrace.h>

BPF_HASH(counts, size_t);

int count(struct pt_regs *ctx) {
    u64 zero = 0, *val;
    u64 key = 1;
    size_t ptr = PT_REGS_PARM1(ctx);
    val = counts.lookup_or_init(&ptr, &zero);
    (*val)++;
    return 0;
};
""")

b.attach_uprobe(name="/home/bork/.rbenv/versions/2.4.0/bin/ruby", sym="newobj_slowpath", fn_name="count")

# header
print("Tracing newobj_slowpath()... Hit Ctrl-C to end.")


counts = b.get_table("counts")

while True:
    sleep(1)
    os.system('clear')
    print("%20s | %s" % ("CLASS POINTER", "COUNT"))
    print("%20s | %s" % ("", ""))
    top = list(reversed(sorted([(counts.get(key).value, key.value) for key in counts.keys()])))
    top = top[:10]
    for (count, ptr) in top:
        print("%20s | %s" % (ptr, count))
    counts.clear()

This can be written more compactly

for count, ptr in islice(sorted(counts.items(), reversed=True)), 10)