[PATCH v5 1/8] x86/resctrl: Add multiple tasks to the resctrl group at once

From: Babu Moger
Date: Thu Jun 01 2023 - 15:01:12 EST


The resctrl task assignment for monitor or control group needs to be
done one at a time. For example:

$mount -t resctrl resctrl /sys/fs/resctrl/
$mkdir /sys/fs/resctrl/ctrl_grp1
$echo 123 > /sys/fs/resctrl/ctrl_grp1/tasks
$echo 456 > /sys/fs/resctrl/ctrl_grp1/tasks
$echo 789 > /sys/fs/resctrl/ctrl_grp1/tasks

This is not user-friendly when dealing with hundreds of tasks.

Support multiple task assignment in one command with tasks ids separated
by commas. For example:
$echo 123,456,789 > /sys/fs/resctrl/ctrl_grp1/tasks

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
Documentation/arch/x86/resctrl.rst | 8 +++++++-
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 30 ++++++++++++++++++++----------
2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index 387ccbcb558f..290f01aa3002 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -292,7 +292,13 @@ All groups contain the following files:
"tasks":
Reading this file shows the list of all tasks that belong to
this group. Writing a task id to the file will add a task to the
- group. If the group is a CTRL_MON group the task is removed from
+ group. Multiple tasks can be added by separating the task ids
+ with commas. Tasks will be assigned sequentially. Multiple
+ failures are not supported. A single failure encountered while
+ attempting to assign a task will cause the operation to abort.
+ Failures will be logged to /sys/fs/resctrl/info/last_cmd_status.
+
+ If the group is a CTRL_MON group the task is removed from
whichever previous CTRL_MON group owned the task and also from
any MON group that owned the task. If the group is a MON group,
then the task must already belong to the CTRL_MON parent of this
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 6ad33f355861..504137a5d31f 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -696,11 +696,10 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct rdtgroup *rdtgrp;
+ char *pid_str;
int ret = 0;
pid_t pid;

- if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
- return -EINVAL;
rdtgrp = rdtgroup_kn_lock_live(of->kn);
if (!rdtgrp) {
rdtgroup_kn_unlock(of->kn);
@@ -708,16 +707,27 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
}
rdt_last_cmd_clear();

- if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED ||
- rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
- ret = -EINVAL;
- rdt_last_cmd_puts("Pseudo-locking in progress\n");
- goto unlock;
- }
+ while (buf && buf[0] != '\0') {
+ pid_str = strim(strsep(&buf, ","));

- ret = rdtgroup_move_task(pid, rdtgrp, of);
+ if (kstrtoint(pid_str, 0, &pid)) {
+ rdt_last_cmd_puts("Task list parsing error\n");
+ ret = -EINVAL;
+ break;
+ }

-unlock:
+ if (pid < 0) {
+ rdt_last_cmd_printf("Invalid pid %d value\n", pid);
+ ret = -EINVAL;
+ break;
+ }
+
+ ret = rdtgroup_move_task(pid, rdtgrp, of);
+ if (ret) {
+ rdt_last_cmd_printf("Error while processing task %d\n", pid);
+ break;
+ }
+ }
rdtgroup_kn_unlock(of->kn);

return ret ?: nbytes;