cgroups_rs/
cpu.rs

1// Copyright (c) 2018 Levente Kurusa
2// Copyright (c) 2020 Ant Group
3//
4// SPDX-License-Identifier: Apache-2.0 or MIT
5//
6
7//! This module contains the implementation of the `cpu` cgroup subsystem.
8//!
9//! See the Kernel's documentation for more information about this subsystem, found at:
10//!  [Documentation/scheduler/sched-design-CFS.txt](https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt)
11//!  paragraph 7 ("GROUP SCHEDULER EXTENSIONS TO CFS").
12use std::fs::File;
13use std::io::{Read, Write};
14use std::path::PathBuf;
15
16use crate::error::ErrorKind::*;
17use crate::error::*;
18use crate::{parse_max_value, read_i64_from, read_u64_from};
19
20use crate::{
21    ControllIdentifier, ControllerInternal, Controllers, CpuResources, CustomizedAttribute,
22    MaxValue, Resources, Subsystem,
23};
24
25/// A controller that allows controlling the `cpu` subsystem of a Cgroup.
26///
27/// In essence, it allows gathering information about how much the tasks inside the control group
28/// are using the CPU and creating rules that limit their usage. Note that this crate does not yet
29/// support managing realtime tasks.
30#[derive(Debug, Clone)]
31pub struct CpuController {
32    base: PathBuf,
33    path: PathBuf,
34    v2: bool,
35}
36
37/// The current state of the control group and its processes.
38#[derive(Debug)]
39#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
40pub struct Cpu {
41    /// Reports CPU time statistics.
42    ///
43    /// Corresponds the `cpu.stat` file in `cpu` control group.
44    pub stat: String,
45}
46
47/// The current state of the control group and its processes.
48#[derive(Debug)]
49struct CfsQuotaAndPeriod {
50    quota: MaxValue,
51    period: u64,
52}
53
54impl ControllerInternal for CpuController {
55    fn control_type(&self) -> Controllers {
56        Controllers::Cpu
57    }
58
59    fn get_path(&self) -> &PathBuf {
60        &self.path
61    }
62
63    fn get_path_mut(&mut self) -> &mut PathBuf {
64        &mut self.path
65    }
66
67    fn get_base(&self) -> &PathBuf {
68        &self.base
69    }
70
71    fn is_v2(&self) -> bool {
72        self.v2
73    }
74
75    fn apply(&self, res: &Resources) -> Result<()> {
76        // get the resources that apply to this controller
77        let res: &CpuResources = &res.cpu;
78
79        update_and_test!(self, set_shares, res.shares, shares);
80        update_and_test!(self, set_cfs_period, res.period, cfs_period);
81        update_and_test!(self, set_cfs_quota, res.quota, cfs_quota);
82
83        res.attrs.iter().for_each(|(k, v)| {
84            let _ = self.set(k, v);
85        });
86
87        // TODO: rt properties (CONFIG_RT_GROUP_SCHED) are not yet supported
88
89        Ok(())
90    }
91}
92
93impl ControllIdentifier for CpuController {
94    fn controller_type() -> Controllers {
95        Controllers::Cpu
96    }
97}
98
99impl<'a> From<&'a Subsystem> for &'a CpuController {
100    fn from(sub: &'a Subsystem) -> &'a CpuController {
101        unsafe {
102            match sub {
103                Subsystem::Cpu(c) => c,
104                _ => {
105                    assert_eq!(1, 0);
106                    let v = std::mem::MaybeUninit::uninit();
107                    v.assume_init()
108                }
109            }
110        }
111    }
112}
113
114impl CpuController {
115    /// Contructs a new `CpuController` with `root` serving as the root of the control group.
116    pub fn new(root: PathBuf, v2: bool) -> Self {
117        Self {
118            base: root.clone(),
119            path: root,
120            v2,
121        }
122    }
123
124    /// Returns CPU time statistics based on the processes in the control group.
125    pub fn cpu(&self) -> Cpu {
126        Cpu {
127            stat: self
128                .open_path("cpu.stat", false)
129                .and_then(|mut file| {
130                    let mut s = String::new();
131                    let res = file.read_to_string(&mut s);
132                    match res {
133                        Ok(_) => Ok(s),
134                        Err(e) => Err(Error::with_cause(ReadFailed("cpu.stat".to_string()), e)),
135                    }
136                })
137                .unwrap_or_default(),
138        }
139    }
140
141    /// Configures the CPU bandwidth (in relative relation to other control groups and this control
142    /// group's parent).
143    ///
144    /// For example, setting control group `A`'s `shares` to `100`, and control group `B`'s
145    /// `shares` to `200` ensures that control group `B` receives twice as much as CPU bandwidth.
146    /// (Assuming both `A` and `B` are of the same parent)
147    pub fn set_shares(&self, shares: u64) -> Result<()> {
148        let mut file_name = "cpu.shares";
149        if self.v2 {
150            file_name = "cpu.weight";
151        }
152        // NOTE: .CpuShares is not used here. Conversion is the caller's responsibility.
153        self.open_path(file_name, true).and_then(|mut file| {
154            file.write_all(shares.to_string().as_ref()).map_err(|e| {
155                Error::with_cause(WriteFailed(file_name.to_string(), shares.to_string()), e)
156            })
157        })
158    }
159
160    /// Retrieve the CPU bandwidth that this control group (relative to other control groups and
161    /// this control group's parent) can use.
162    pub fn shares(&self) -> Result<u64> {
163        let mut file = "cpu.shares";
164        if self.v2 {
165            file = "cpu.weight";
166        }
167        self.open_path(file, false).and_then(read_u64_from)
168    }
169
170    /// Specify a period (when using the CFS scheduler) of time in microseconds for how often this
171    /// control group's access to the CPU should be reallocated.
172    pub fn set_cfs_period(&self, us: u64) -> Result<()> {
173        if self.v2 {
174            return self.set_cfs_quota_and_period(None, Some(us));
175        }
176        self.open_path("cpu.cfs_period_us", true)
177            .and_then(|mut file| {
178                file.write_all(us.to_string().as_ref()).map_err(|e| {
179                    Error::with_cause(
180                        WriteFailed("cpu.cfs_period_us".to_string(), us.to_string()),
181                        e,
182                    )
183                })
184            })
185    }
186
187    /// Retrieve the period of time of how often this cgroup's access to the CPU should be
188    /// reallocated in microseconds.
189    pub fn cfs_period(&self) -> Result<u64> {
190        if self.v2 {
191            let current_value = self
192                .open_path("cpu.max", false)
193                .and_then(parse_cfs_quota_and_period)?;
194            return Ok(current_value.period);
195        }
196        self.open_path("cpu.cfs_period_us", false)
197            .and_then(read_u64_from)
198    }
199
200    /// Specify a quota (when using the CFS scheduler) of time in microseconds for which all tasks
201    /// in this control group can run during one period (see: `set_cfs_period()`).
202    pub fn set_cfs_quota(&self, us: i64) -> Result<()> {
203        if self.v2 {
204            return self.set_cfs_quota_and_period(Some(us), None);
205        }
206        self.open_path("cpu.cfs_quota_us", true)
207            .and_then(|mut file| {
208                file.write_all(us.to_string().as_ref()).map_err(|e| {
209                    Error::with_cause(
210                        WriteFailed("cpu.cfs_quota_us".to_string(), us.to_string()),
211                        e,
212                    )
213                })
214            })
215    }
216
217    /// Retrieve the quota of time for which all tasks in this cgroup can run during one period, in
218    /// microseconds.
219    pub fn cfs_quota(&self) -> Result<i64> {
220        if self.v2 {
221            let current_value = self
222                .open_path("cpu.max", false)
223                .and_then(parse_cfs_quota_and_period)?;
224            return Ok(current_value.quota.to_i64());
225        }
226
227        self.open_path("cpu.cfs_quota_us", false)
228            .and_then(read_i64_from)
229    }
230
231    pub fn set_cfs_quota_and_period(&self, quota: Option<i64>, period: Option<u64>) -> Result<()> {
232        if !self.v2 {
233            if let Some(q) = quota {
234                self.set_cfs_quota(q)?;
235            }
236            if let Some(p) = period {
237                self.set_cfs_period(p)?;
238            }
239            return Ok(());
240        }
241
242        // https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
243
244        // cpu.max
245        // A read-write two value file which exists on non-root cgroups. The default is “max 100000”.
246        // The maximum bandwidth limit. It’s in the following format:
247        // $MAX $PERIOD
248        // which indicates that the group may consume upto $MAX in each $PERIOD duration.
249        // “max” for $MAX indicates no limit. If only one number is written, $MAX is updated.
250
251        let current_value = self
252            .open_path("cpu.max", false)
253            .and_then(parse_cfs_quota_and_period)?;
254
255        let new_quota = if let Some(q) = quota {
256            if q > 0 {
257                q.to_string()
258            } else {
259                "max".to_string()
260            }
261        } else {
262            current_value.quota.to_string()
263        };
264
265        let new_period = if let Some(p) = period {
266            p.to_string()
267        } else {
268            current_value.period.to_string()
269        };
270
271        let line = format!("{} {}", new_quota, new_period);
272        self.open_path("cpu.max", true).and_then(|mut file| {
273            file.write_all(line.as_ref())
274                .map_err(|e| Error::with_cause(WriteFailed("cpu.max".to_string(), line), e))
275        })
276    }
277
278    pub fn set_rt_runtime(&self, us: i64) -> Result<()> {
279        self.open_path("cpu.rt_runtime_us", true)
280            .and_then(|mut file| {
281                file.write_all(us.to_string().as_ref()).map_err(|e| {
282                    Error::with_cause(
283                        WriteFailed("cpu.rt_runtime_us".to_string(), us.to_string()),
284                        e,
285                    )
286                })
287            })
288    }
289
290    pub fn set_rt_period_us(&self, us: u64) -> Result<()> {
291        self.open_path("cpu.rt_period_us", true)
292            .and_then(|mut file| {
293                file.write_all(us.to_string().as_ref()).map_err(|e| {
294                    Error::with_cause(
295                        WriteFailed("cpu.rt_period_us".to_string(), us.to_string()),
296                        e,
297                    )
298                })
299            })
300    }
301}
302
303impl CustomizedAttribute for CpuController {}
304
305fn parse_cfs_quota_and_period(mut file: File) -> Result<CfsQuotaAndPeriod> {
306    let mut content = String::new();
307    file.read_to_string(&mut content)
308        .map_err(|e| Error::with_cause(ReadFailed("cpu.max".to_string()), e))?;
309
310    let fields = content.trim().split(' ').collect::<Vec<&str>>();
311    if fields.len() != 2 {
312        return Err(Error::from_string(format!("invaild format: {}", content)));
313    }
314
315    let quota = parse_max_value(fields[0])?;
316    let period = fields[1]
317        .parse::<u64>()
318        .map_err(|e| Error::with_cause(ParseError, e))?;
319
320    Ok(CfsQuotaAndPeriod { quota, period })
321}
cgroups_rs/cpu.rs

cgroups_rs/
cpu.rs
