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drsnoop.bpf.c
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drsnoop.bpf.c
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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2020 Wenbo Zhang
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include "drsnoop.h"
const volatile pid_t targ_pid = 0;
const volatile pid_t targ_tgid = 0;
const volatile __u64 vm_zone_stat_kaddr = 0;
struct piddata {
u64 ts;
u64 nr_free_pages;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 8192);
__type(key, u32);
__type(value, struct piddata);
} start SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__uint(key_size, sizeof(u32));
__uint(value_size, sizeof(u32));
} events SEC(".maps");
SEC("tp_btf/mm_vmscan_direct_reclaim_begin")
int handle__mm_vmscan_direct_reclaim_begin(u64 *ctx)
{
u64 *vm_zone_stat_kaddrp = (u64*)vm_zone_stat_kaddr;
u64 id = bpf_get_current_pid_tgid();
struct piddata piddata = {};
u32 tgid = id >> 32;
u32 pid = id;
if (targ_tgid && targ_tgid != tgid)
return 0;
if (targ_pid && targ_pid != pid)
return 0;
piddata.ts = bpf_ktime_get_ns();
if (vm_zone_stat_kaddrp) {
bpf_probe_read_kernel(&piddata.nr_free_pages,
sizeof(*vm_zone_stat_kaddrp),
&vm_zone_stat_kaddrp[NR_FREE_PAGES]);
}
bpf_map_update_elem(&start, &pid, &piddata, 0);
return 0;
}
SEC("tp_btf/mm_vmscan_direct_reclaim_end")
int handle__mm_vmscan_direct_reclaim_end(u64 *ctx)
{
u64 id = bpf_get_current_pid_tgid();
/* TP_PROTO(unsigned long nr_reclaimed) */
u64 nr_reclaimed = ctx[0];
struct piddata *piddatap;
struct event event = {};
u32 tgid = id >> 32;
u32 pid = id;
u64 delta_ns;
if (targ_tgid && targ_tgid != tgid)
return 0;
if (targ_pid && targ_pid != pid)
return 0;
/* fetch timestamp and calculate delta */
piddatap = bpf_map_lookup_elem(&start, &pid);
if (!piddatap)
return 0; /* missed entry */
delta_ns = bpf_ktime_get_ns() - piddatap->ts;
event.pid = pid;
event.nr_reclaimed = nr_reclaimed;
event.delta_ns = delta_ns;
event.nr_free_pages = piddatap->nr_free_pages;
bpf_get_current_comm(&event.task, TASK_COMM_LEN);
/* output */
bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU,
&event, sizeof(event));
bpf_map_delete_elem(&start, &pid);
return 0;
}
char LICENSE[] SEC("license") = "GPL";