90 lines
1.9 KiB
C
90 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2020 Wenbo Zhang
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#include <vmlinux.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#include "readahead.h"
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#include "bits.bpf.h"
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#define MAX_ENTRIES 10240
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, MAX_ENTRIES);
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__type(key, u32);
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__type(value, u64);
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__uint(map_flags, BPF_F_NO_PREALLOC);
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} in_readahead SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, MAX_ENTRIES);
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__type(key, struct page *);
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__type(value, u64);
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__uint(map_flags, BPF_F_NO_PREALLOC);
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} birth SEC(".maps");
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struct hist hist = {};
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SEC("fentry/do_page_cache_ra")
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int BPF_PROG(do_page_cache_ra)
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{
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u32 pid = bpf_get_current_pid_tgid();
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u64 one = 1;
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bpf_map_update_elem(&in_readahead, &pid, &one, 0);
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return 0;
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}
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SEC("fexit/__page_cache_alloc")
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int BPF_PROG(page_cache_alloc_ret, gfp_t gfp, struct page *ret)
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{
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u32 pid = bpf_get_current_pid_tgid();
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u64 ts;
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if (!bpf_map_lookup_elem(&in_readahead, &pid))
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return 0;
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ts = bpf_ktime_get_ns();
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bpf_map_update_elem(&birth, &ret, &ts, 0);
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__sync_fetch_and_add(&hist.unused, 1);
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__sync_fetch_and_add(&hist.total, 1);
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return 0;
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}
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SEC("fexit/do_page_cache_ra")
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int BPF_PROG(do_page_cache_ra_ret)
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{
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u32 pid = bpf_get_current_pid_tgid();
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bpf_map_delete_elem(&in_readahead, &pid);
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return 0;
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}
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SEC("fentry/mark_page_accessed")
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int BPF_PROG(mark_page_accessed, struct page *page)
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{
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u64 *tsp, slot, ts = bpf_ktime_get_ns();
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s64 delta;
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tsp = bpf_map_lookup_elem(&birth, &page);
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if (!tsp)
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return 0;
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delta = (s64)(ts - *tsp);
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if (delta < 0)
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goto update_and_cleanup;
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slot = log2l(delta / 1000000U);
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if (slot >= MAX_SLOTS)
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slot = MAX_SLOTS - 1;
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__sync_fetch_and_add(&hist.slots[slot], 1);
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update_and_cleanup:
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__sync_fetch_and_add(&hist.unused, -1);
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bpf_map_delete_elem(&birth, &page);
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return 0;
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}
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char LICENSE[] SEC("license") = "GPL";
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