ktstr 0.4.23

Test harness for Linux process schedulers
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219

//! BTF offsets for `struct sched_domain` tree walking and the
//! `CONFIG_SCHEDSTATS` load-balancing stats fields it carries.
//!
//! `rq->sd` is a per-CPU pointer to the lowest-level domain; the
//! domain tree is walked via `sd->parent` until NULL. Runtime fields
//! (`balance_interval`, `nr_balance_failed`, `max_newidle_lb_cost`)
//! are unconditional. `newidle_call` / `newidle_success` /
//! `newidle_ratio` were added together in 6.19 (proportional newidle
//! balance — kernel commit 33cf66d88306) and are absent on older
//! kernels, so the resolver returns them as optional. Load-balancing
//! stats fields (`lb_count`, `alb_pushed`, `ttwu_wake_remote`, etc.)
//! are gated on `CONFIG_SCHEDSTATS` and resolved into an optional
//! [`SchedDomainStatsOffsets`].

use anyhow::Result;
use btf_rs::Btf;

use super::{find_struct, member_byte_offset};

/// Byte offsets for walking the `struct sched_domain` tree from guest memory.
///
/// `rq->sd` is a per-CPU pointer to the lowest-level domain. The domain
/// tree is walked via `sd->parent` until NULL. Resolution returns `Err`
/// when the `sd` field is missing from `struct rq` or when `struct
/// sched_domain` is absent from BTF.
///
/// Runtime fields (`balance_interval`, `nr_balance_failed`,
/// `max_newidle_lb_cost`) are always present on `struct sched_domain`.
/// `newidle_call`, `newidle_success`, and `newidle_ratio` were added
/// together in 6.19 and are absent on older kernels, so they are
/// resolved as optional.
/// Load balancing stats (`lb_count`, `alb_pushed`, `ttwu_wake_remote`,
/// etc.) are guarded by `CONFIG_SCHEDSTATS` and resolved separately
/// into an optional [`SchedDomainStatsOffsets`].
#[derive(Debug, Clone)]
pub struct SchedDomainOffsets {
    /// Offset of `sd` (pointer) within `struct rq`.
    pub rq_sd: usize,
    /// Offset of `parent` (pointer) within `struct sched_domain`.
    pub sd_parent: usize,
    /// Offset of `level` (int) within `struct sched_domain`.
    pub sd_level: usize,
    /// Offset of `name` (char *) within `struct sched_domain`.
    pub sd_name: usize,
    /// Offset of `flags` (int) within `struct sched_domain`.
    pub sd_flags: usize,
    /// Offset of `span_weight` (unsigned int) within `struct sched_domain`.
    pub sd_span_weight: usize,

    // -- Runtime fields --
    /// Offset of `balance_interval` (unsigned int) within `struct sched_domain`.
    pub sd_balance_interval: usize,
    /// Offset of `nr_balance_failed` (unsigned int) within `struct sched_domain`.
    pub sd_nr_balance_failed: usize,
    /// Offset of `newidle_call` (unsigned int) within `struct sched_domain`.
    /// None on pre-6.19 kernels where this field had not yet been added.
    pub sd_newidle_call: Option<usize>,
    /// Offset of `newidle_success` (unsigned int) within `struct sched_domain`.
    /// None on pre-6.19 kernels where this field had not yet been added.
    pub sd_newidle_success: Option<usize>,
    /// Offset of `newidle_ratio` (unsigned int) within `struct sched_domain`.
    /// None on pre-6.19 kernels where this field had not yet been added.
    pub sd_newidle_ratio: Option<usize>,
    /// Offset of `max_newidle_lb_cost` (u64) within `struct sched_domain`.
    pub sd_max_newidle_lb_cost: usize,

    /// CONFIG_SCHEDSTATS load balancing stats offsets. None when
    /// CONFIG_SCHEDSTATS is not enabled.
    pub stats_offsets: Option<SchedDomainStatsOffsets>,
}

/// Byte offsets for CONFIG_SCHEDSTATS fields on `struct sched_domain`.
///
/// Array fields are `unsigned int field[CPU_MAX_IDLE_TYPES]` where
/// `CPU_MAX_IDLE_TYPES = 3`. The offset is to element 0; element i
/// is at `offset + i * 4`.
#[derive(Debug, Clone)]
pub struct SchedDomainStatsOffsets {
    // Array fields indexed by cpu_idle_type.
    /// Offset of `lb_count[0]` within `struct sched_domain`.
    pub sd_lb_count: usize,
    /// Offset of `lb_failed[0]` within `struct sched_domain`.
    pub sd_lb_failed: usize,
    /// Offset of `lb_balanced[0]` within `struct sched_domain`.
    pub sd_lb_balanced: usize,
    /// Offset of `lb_imbalance_load[0]` within `struct sched_domain`.
    pub sd_lb_imbalance_load: usize,
    /// Offset of `lb_imbalance_util[0]` within `struct sched_domain`.
    pub sd_lb_imbalance_util: usize,
    /// Offset of `lb_imbalance_task[0]` within `struct sched_domain`.
    pub sd_lb_imbalance_task: usize,
    /// Offset of `lb_imbalance_misfit[0]` within `struct sched_domain`.
    pub sd_lb_imbalance_misfit: usize,
    /// Offset of `lb_gained[0]` within `struct sched_domain`.
    pub sd_lb_gained: usize,
    /// Offset of `lb_hot_gained[0]` within `struct sched_domain`.
    pub sd_lb_hot_gained: usize,
    /// Offset of `lb_nobusyg[0]` within `struct sched_domain`.
    pub sd_lb_nobusyg: usize,
    /// Offset of `lb_nobusyq[0]` within `struct sched_domain`.
    pub sd_lb_nobusyq: usize,

    // Scalar fields.
    /// Offset of `alb_count` within `struct sched_domain`.
    pub sd_alb_count: usize,
    /// Offset of `alb_failed` within `struct sched_domain`.
    pub sd_alb_failed: usize,
    /// Offset of `alb_pushed` within `struct sched_domain`.
    pub sd_alb_pushed: usize,
    /// Offset of `sbe_count` within `struct sched_domain`.
    pub sd_sbe_count: usize,
    /// Offset of `sbe_balanced` within `struct sched_domain`.
    pub sd_sbe_balanced: usize,
    /// Offset of `sbe_pushed` within `struct sched_domain`.
    pub sd_sbe_pushed: usize,
    /// Offset of `sbf_count` within `struct sched_domain`.
    pub sd_sbf_count: usize,
    /// Offset of `sbf_balanced` within `struct sched_domain`.
    pub sd_sbf_balanced: usize,
    /// Offset of `sbf_pushed` within `struct sched_domain`.
    pub sd_sbf_pushed: usize,
    /// Offset of `ttwu_wake_remote` within `struct sched_domain`.
    pub sd_ttwu_wake_remote: usize,
    /// Offset of `ttwu_move_affine` within `struct sched_domain`.
    pub sd_ttwu_move_affine: usize,
    /// Offset of `ttwu_move_balance` within `struct sched_domain`.
    pub sd_ttwu_move_balance: usize,
}

/// Number of idle types for array-indexed sched_domain stats fields.
/// `CPU_MAX_IDLE_TYPES = 3`: CPU_NOT_IDLE, CPU_IDLE, CPU_NEWLY_IDLE.
pub const CPU_MAX_IDLE_TYPES: usize = 3;

/// Resolve BTF offsets for sched_domain tree walking and stats.
/// Returns Err if `rq.sd` is missing or `struct sched_domain` is absent.
/// CONFIG_SCHEDSTATS fields are resolved separately and stored in
/// `stats_offsets` (None when CONFIG_SCHEDSTATS is off).
pub(super) fn resolve_sched_domain_offsets(
    btf: &Btf,
    rq_struct: &btf_rs::Struct,
) -> Result<SchedDomainOffsets> {
    let rq_sd = member_byte_offset(btf, rq_struct, "sd")?;

    let (sd_struct, _) = find_struct(btf, "sched_domain")?;
    let sd_parent = member_byte_offset(btf, &sd_struct, "parent")?;
    let sd_level = member_byte_offset(btf, &sd_struct, "level")?;
    let sd_name = member_byte_offset(btf, &sd_struct, "name")?;
    let sd_flags = member_byte_offset(btf, &sd_struct, "flags")?;
    let sd_span_weight = member_byte_offset(btf, &sd_struct, "span_weight")?;

    // Runtime fields.
    let sd_balance_interval = member_byte_offset(btf, &sd_struct, "balance_interval")?;
    let sd_nr_balance_failed = member_byte_offset(btf, &sd_struct, "nr_balance_failed")?;
    let sd_max_newidle_lb_cost = member_byte_offset(btf, &sd_struct, "max_newidle_lb_cost")?;

    // newidle_call/newidle_success/newidle_ratio were added together
    // in 6.19 and are absent on older kernels. Resolve all-or-nothing:
    // if any is missing, set all to None.
    let (sd_newidle_call, sd_newidle_success, sd_newidle_ratio) = match (
        member_byte_offset(btf, &sd_struct, "newidle_call").ok(),
        member_byte_offset(btf, &sd_struct, "newidle_success").ok(),
        member_byte_offset(btf, &sd_struct, "newidle_ratio").ok(),
    ) {
        (Some(c), Some(s), Some(r)) => (Some(c), Some(s), Some(r)),
        _ => (None, None, None),
    };

    // CONFIG_SCHEDSTATS fields (optional).
    let stats_offsets = resolve_sched_domain_stats_offsets(btf, &sd_struct).ok();

    Ok(SchedDomainOffsets {
        rq_sd,
        sd_parent,
        sd_level,
        sd_name,
        sd_flags,
        sd_span_weight,
        sd_balance_interval,
        sd_nr_balance_failed,
        sd_newidle_call,
        sd_newidle_success,
        sd_newidle_ratio,
        sd_max_newidle_lb_cost,
        stats_offsets,
    })
}

/// Resolve CONFIG_SCHEDSTATS field offsets on struct sched_domain.
/// Returns Err if any required field is missing.
fn resolve_sched_domain_stats_offsets(
    btf: &Btf,
    sd_struct: &btf_rs::Struct,
) -> Result<SchedDomainStatsOffsets> {
    Ok(SchedDomainStatsOffsets {
        sd_lb_count: member_byte_offset(btf, sd_struct, "lb_count")?,
        sd_lb_failed: member_byte_offset(btf, sd_struct, "lb_failed")?,
        sd_lb_balanced: member_byte_offset(btf, sd_struct, "lb_balanced")?,
        sd_lb_imbalance_load: member_byte_offset(btf, sd_struct, "lb_imbalance_load")?,
        sd_lb_imbalance_util: member_byte_offset(btf, sd_struct, "lb_imbalance_util")?,
        sd_lb_imbalance_task: member_byte_offset(btf, sd_struct, "lb_imbalance_task")?,
        sd_lb_imbalance_misfit: member_byte_offset(btf, sd_struct, "lb_imbalance_misfit")?,
        sd_lb_gained: member_byte_offset(btf, sd_struct, "lb_gained")?,
        sd_lb_hot_gained: member_byte_offset(btf, sd_struct, "lb_hot_gained")?,
        sd_lb_nobusyg: member_byte_offset(btf, sd_struct, "lb_nobusyg")?,
        sd_lb_nobusyq: member_byte_offset(btf, sd_struct, "lb_nobusyq")?,
        sd_alb_count: member_byte_offset(btf, sd_struct, "alb_count")?,
        sd_alb_failed: member_byte_offset(btf, sd_struct, "alb_failed")?,
        sd_alb_pushed: member_byte_offset(btf, sd_struct, "alb_pushed")?,
        sd_sbe_count: member_byte_offset(btf, sd_struct, "sbe_count")?,
        sd_sbe_balanced: member_byte_offset(btf, sd_struct, "sbe_balanced")?,
        sd_sbe_pushed: member_byte_offset(btf, sd_struct, "sbe_pushed")?,
        sd_sbf_count: member_byte_offset(btf, sd_struct, "sbf_count")?,
        sd_sbf_balanced: member_byte_offset(btf, sd_struct, "sbf_balanced")?,
        sd_sbf_pushed: member_byte_offset(btf, sd_struct, "sbf_pushed")?,
        sd_ttwu_wake_remote: member_byte_offset(btf, sd_struct, "ttwu_wake_remote")?,
        sd_ttwu_move_affine: member_byte_offset(btf, sd_struct, "ttwu_move_affine")?,
        sd_ttwu_move_balance: member_byte_offset(btf, sd_struct, "ttwu_move_balance")?,
    })
}