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biostacks.bpf.c
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biostacks.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 <bpf/bpf_core_read.h>
#include <bpf/bpf_tracing.h>
#include "biostacks.h"
#include "bits.bpf.h"
#include "maps.bpf.h"
#define MAX_ENTRIES 10240
const volatile bool targ_ms = false;
const volatile bool filter_dev = false;
const volatile __u32 targ_dev = -1;
struct request_queue___x {
struct gendisk *disk;
} __attribute__((preserve_access_index));
struct internal_rqinfo {
u64 start_ts;
struct rqinfo rqinfo;
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, MAX_ENTRIES);
__type(key, struct request *);
__type(value, struct internal_rqinfo);
__uint(map_flags, BPF_F_NO_PREALLOC);
} rqinfos SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, MAX_ENTRIES);
__type(key, struct rqinfo);
__type(value, struct hist);
__uint(map_flags, BPF_F_NO_PREALLOC);
} hists SEC(".maps");
static struct hist zero;
static __always_inline
int trace_start(void *ctx, struct request *rq, bool merge_bio)
{
struct internal_rqinfo *i_rqinfop = NULL, i_rqinfo = {};
struct request_queue___x *q = (void *)BPF_CORE_READ(rq, q);
struct gendisk *disk;
u32 dev;
if (bpf_core_field_exists(q->disk))
disk = BPF_CORE_READ(q, disk);
else
disk = BPF_CORE_READ(rq, rq_disk);
dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
BPF_CORE_READ(disk, first_minor)) : 0;
if (filter_dev && targ_dev != dev)
return 0;
if (merge_bio)
i_rqinfop = bpf_map_lookup_elem(&rqinfos, &rq);
if (!i_rqinfop)
i_rqinfop = &i_rqinfo;
i_rqinfop->start_ts = bpf_ktime_get_ns();
i_rqinfop->rqinfo.pid = bpf_get_current_pid_tgid();
i_rqinfop->rqinfo.kern_stack_size =
bpf_get_stack(ctx, i_rqinfop->rqinfo.kern_stack,
sizeof(i_rqinfop->rqinfo.kern_stack), 0);
bpf_get_current_comm(&i_rqinfop->rqinfo.comm,
sizeof(&i_rqinfop->rqinfo.comm));
i_rqinfop->rqinfo.dev = dev;
if (i_rqinfop == &i_rqinfo)
bpf_map_update_elem(&rqinfos, &rq, i_rqinfop, 0);
return 0;
}
SEC("fentry/blk_account_io_start")
int BPF_PROG(blk_account_io_start, struct request *rq)
{
return trace_start(ctx, rq, false);
}
SEC("kprobe/blk_account_io_merge_bio")
int BPF_KPROBE(blk_account_io_merge_bio, struct request *rq)
{
return trace_start(ctx, rq, true);
}
SEC("fentry/blk_account_io_done")
int BPF_PROG(blk_account_io_done, struct request *rq)
{
u64 slot, ts = bpf_ktime_get_ns();
struct internal_rqinfo *i_rqinfop;
struct hist *histp;
s64 delta;
i_rqinfop = bpf_map_lookup_elem(&rqinfos, &rq);
if (!i_rqinfop)
return 0;
delta = (s64)(ts - i_rqinfop->start_ts);
if (delta < 0)
goto cleanup;
histp = bpf_map_lookup_or_try_init(&hists, &i_rqinfop->rqinfo, &zero);
if (!histp)
goto cleanup;
if (targ_ms)
delta /= 1000000U;
else
delta /= 1000U;
slot = log2l(delta);
if (slot >= MAX_SLOTS)
slot = MAX_SLOTS - 1;
__sync_fetch_and_add(&histp->slots[slot], 1);
cleanup:
bpf_map_delete_elem(&rqinfos, &rq);
return 0;
}
char LICENSE[] SEC("license") = "GPL";