forked from Minki/linux
e3edfdec04
the first microbenchmark does
fd=open("/proc/self/comm");
for() {
write(fd, "test");
}
and on 4 cpus in parallel:
writes per sec
base (no tracepoints, no kprobes) 930k
with kprobe at __set_task_comm() 420k
with tracepoint at task:task_rename 730k
For kprobe + full bpf program manully fetches oldcomm, newcomm via bpf_probe_read.
For tracepint bpf program does nothing, since arguments are copied by tracepoint.
2nd microbenchmark does:
fd=open("/dev/urandom");
for() {
read(fd, buf);
}
and on 4 cpus in parallel:
reads per sec
base (no tracepoints, no kprobes) 300k
with kprobe at urandom_read() 279k
with tracepoint at random:urandom_read 290k
bpf progs attached to kprobe and tracepoint are noop.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
42 lines
1.0 KiB
C
42 lines
1.0 KiB
C
/* Copyright (c) 2016 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <linux/version.h>
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#include <linux/ptrace.h>
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#include <uapi/linux/bpf.h>
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#include "bpf_helpers.h"
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#define _(P) ({typeof(P) val = 0; bpf_probe_read(&val, sizeof(val), &P); val;})
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SEC("kprobe/__set_task_comm")
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int prog(struct pt_regs *ctx)
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{
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struct signal_struct *signal;
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struct task_struct *tsk;
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char oldcomm[16] = {};
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char newcomm[16] = {};
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u16 oom_score_adj;
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u32 pid;
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tsk = (void *)PT_REGS_PARM1(ctx);
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pid = _(tsk->pid);
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bpf_probe_read(oldcomm, sizeof(oldcomm), &tsk->comm);
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bpf_probe_read(newcomm, sizeof(newcomm), (void *)PT_REGS_PARM2(ctx));
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signal = _(tsk->signal);
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oom_score_adj = _(signal->oom_score_adj);
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return 0;
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}
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SEC("kprobe/urandom_read")
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int prog2(struct pt_regs *ctx)
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{
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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u32 _version SEC("version") = LINUX_VERSION_CODE;
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