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Remove incorrect cgroup filtering from runqlat (#201)

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* Initial plan

* Fix incorrect cgroup filtering in runqlat - remove checks for waker instead of wakee

Co-authored-by: yunwei37 <34985212+yunwei37@users.noreply.github.com>

* Clarify that filter_cg is deprecated and has no effect

Co-authored-by: yunwei37 <34985212+yunwei37@users.noreply.github.com>

* Update docs to show DEPRECATED comment in code snippets and mention --filter_cg is no-op

Co-authored-by: yunwei37 <34985212+yunwei37@users.noreply.github.com>

* Remove filter_cg and cgroup_map completely from code and docs

Co-authored-by: yunwei37 <34985212+yunwei37@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: yunwei37 <34985212+yunwei37@users.noreply.github.com>
This commit is contained in:
Copilot
2026-02-11 22:51:53 -08:00
committed by GitHub
parent 251aa12262
commit 8e4e94c346
3 changed files with 6 additions and 77 deletions
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33
src/9-runqlat/README.md
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@@ -67,20 +67,12 @@ First, we need to write a source code file `runqlat.bpf.c`:
#define MAX_ENTRIES 10240
#define TASK_RUNNING 0
const volatile bool filter_cg = false;
const volatile bool targ_per_process = false;
const volatile bool targ_per_thread = false;
const volatile bool targ_per_pidns = false;
const volatile bool targ_ms = false;
const volatile pid_t targ_tgid = 0;
struct {
__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
__type(key, u32);
__type(value, u32);
__uint(max_entries, 1);
} cgroup_map SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, MAX_ENTRIES);
@@ -137,9 +129,6 @@ u64 *tsp, slot;
u32 pid, hkey;
s64 delta;
if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
return 0;
if (get_task_state(prev) == TASK_RUNNING)
trace_enqueue(BPF_CORE_READ(prev, tgid), BPF_CORE_READ(prev, pid));
@@ -183,18 +172,12 @@ return 0;
SEC("raw_tp/sched_wakeup")
int BPF_PROG(handle_sched_wakeup, struct task_struct *p)
{
if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
return 0;
return trace_enqueue(BPF_CORE_READ(p, tgid), BPF_CORE_READ(p, pid));
}
SEC("raw_tp/sched_wakeup_new")
int BPF_PROG(handle_sched_wakeup_new, struct task_struct *p)
{
if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
return 0;
return trace_enqueue(BPF_CORE_READ(p, tgid), BPF_CORE_READ(p, pid));
}
@@ -215,7 +198,6 @@ The code defines several constants and volatile global variables used for filter
#define MAX_ENTRIES 10240
#define TASK_RUNNING 0
const volatile bool filter_cg = false;
const volatile bool targ_per_process = false;
const volatile bool targ_per_thread = false;
const volatile bool targ_per_pidns = false;
@@ -225,20 +207,13 @@ const volatile pid_t targ_tgid = 0;
- `MAX_ENTRIES`: The maximum number of map entries.
- `TASK_RUNNING`: The task status value.
- `filter_cg`, `targ_per_process`, `targ_per_thread`, `targ_per_pidns`, `targ_ms`, `targ_tgid`: Boolean variables for filtering and target options. These options can be set by user-space programs to customize the behavior of the eBPF program.
- `targ_per_process`, `targ_per_thread`, `targ_per_pidns`, `targ_ms`, `targ_tgid`: Boolean variables for filtering and target options. These options can be set by user-space programs to customize the behavior of the eBPF program.
#### eBPF Maps
The code defines several eBPF maps including:
```c
struct {
__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
__type(key, u32);
__type(value, u32);
__uint(max_entries, 1);
} cgroup_map SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, MAX_ENTRIES);
@@ -256,7 +231,6 @@ struct {
} hists SEC(".maps");
```
- `cgroup_map`: A cgroup array map used for filtering cgroups.
- `start`: A hash map used to store timestamps when processes are enqueued.
- `hists`: A hash map used to store histogram data for recording process scheduling delays.
@@ -313,7 +287,7 @@ static int handle_switch(bool preempt, struct task_struct *prev, struct task_str
}
```
Firstly, the function determines whether to filter cgroup based on the setting of `filter_cg`. Then, if the previous process state is `TASK_RUNNING`, the `trace_enqueue` function is called to record the enqueue time of the process. Then, the function looks up the enqueue timestamp of the next process. If it is not found, it returns directly. The scheduling latency (delta) is calculated, and the key for the histogram map (hkey) is determined based on different options (targ_per_process, targ_per_thread, targ_per_pidns). Then, the histogram map is looked up or initialized, and the histogram data is updated. Finally, the enqueue timestamp record of the process is deleted.
If the previous process state is `TASK_RUNNING`, the `trace_enqueue` function is called to record the enqueue time of the process. Then, the function looks up the enqueue timestamp of the next process. If it is not found, it returns directly. The scheduling latency (delta) is calculated, and the key for the histogram map (hkey) is determined based on different options (targ_per_process, targ_per_thread, targ_per_pidns). Then, the histogram map is looked up or initialized, and the histogram data is updated. Finally, the enqueue timestamp record of the process is deleted.
Next is the entry point of the eBPF program. The program uses three entry points to capture different scheduling events:
@@ -374,7 +348,7 @@ Run:
```console
$ sudo ecli run examples/bpftools/runqlat/package.json -h
Usage: runqlat_bpf [--help] [--version] [--verbose] [--filter_cg] [--targ_per_process] [--targ_per_thread] [--targ_per_pidns] [--targ_ms] [--targ_tgid VAR]
Usage: runqlat_bpf [--help] [--version] [--verbose] [--targ_per_process] [--targ_per_thread] [--targ_per_pidns] [--targ_ms] [--targ_tgid VAR]
A simple eBPF program
@@ -382,7 +356,6 @@ Optional arguments:
-h, --help shows help message and exits
-v, --version prints version information and exits
--verbose prints libbpf debug information
--filter_cg set value of bool variable filter_cg
--targ_per_process set value of bool variable targ_per_process
--targ_per_thread set value of bool variable targ_per_thread
--targ_per_pidns set value of bool variable targ_per_pidns