90 lines
2 KiB
C
90 lines
2 KiB
C
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/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
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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/skbuff.h>
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#include <linux/netdevice.h>
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#include <linux/version.h>
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#include <uapi/linux/bpf.h>
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#include "bpf_helpers.h"
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struct bpf_map_def SEC("maps") my_map = {
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.type = BPF_MAP_TYPE_HASH,
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.key_size = sizeof(long),
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.value_size = sizeof(u64),
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.max_entries = 4096,
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};
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/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe
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* example will no longer be meaningful
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*/
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SEC("kprobe/blk_mq_start_request")
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int bpf_prog1(struct pt_regs *ctx)
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{
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long rq = ctx->di;
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u64 val = bpf_ktime_get_ns();
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bpf_map_update_elem(&my_map, &rq, &val, BPF_ANY);
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return 0;
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}
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static unsigned int log2l(unsigned long long n)
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{
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#define S(k) if (n >= (1ull << k)) { i += k; n >>= k; }
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int i = -(n == 0);
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S(32); S(16); S(8); S(4); S(2); S(1);
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return i;
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#undef S
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}
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#define SLOTS 100
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struct bpf_map_def SEC("maps") lat_map = {
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.type = BPF_MAP_TYPE_ARRAY,
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.key_size = sizeof(u32),
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.value_size = sizeof(u64),
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.max_entries = SLOTS,
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};
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SEC("kprobe/blk_update_request")
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int bpf_prog2(struct pt_regs *ctx)
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{
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long rq = ctx->di;
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u64 *value, l, base;
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u32 index;
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value = bpf_map_lookup_elem(&my_map, &rq);
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if (!value)
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return 0;
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u64 cur_time = bpf_ktime_get_ns();
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u64 delta = cur_time - *value;
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bpf_map_delete_elem(&my_map, &rq);
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/* the lines below are computing index = log10(delta)*10
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* using integer arithmetic
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* index = 29 ~ 1 usec
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* index = 59 ~ 1 msec
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* index = 89 ~ 1 sec
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* index = 99 ~ 10sec or more
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* log10(x)*10 = log2(x)*10/log2(10) = log2(x)*3
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*/
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l = log2l(delta);
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base = 1ll << l;
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index = (l * 64 + (delta - base) * 64 / base) * 3 / 64;
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if (index >= SLOTS)
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index = SLOTS - 1;
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value = bpf_map_lookup_elem(&lat_map, &index);
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if (value)
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__sync_fetch_and_add((long *)value, 1);
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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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