[PATCH v4 1/7] x86/resctrl: Add multiple tasks to the resctrl group at once

Babu Moger
2023-04-17T23:34:27Z

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/clos1
$echo 123 > /sys/fs/resctrl/clos1/tasks
$echo 456 > /sys/fs/resctrl/clos1/tasks
$echo 789 > /sys/fs/resctrl/clos1/tasks

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

It can be improved by supporting the multiple task id assignment in
one command with the tasks separated by commas. For example:

$echo 123,456,789 > /sys/fs/resctrl/clos1/tasks

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
Documentation/x86/resctrl.rst | 9 ++++++++-
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 31 ++++++++++++++++++++++++++++++-
2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
index 387ccbcb558f..f28ed1443a6a 100644
--- a/Documentation/x86/resctrl.rst
+++ b/Documentation/x86/resctrl.rst
@@ -292,7 +292,14 @@ 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 in the order it
+ is entered. Failures while assigning the tasks will be aborted
+ immediately and tasks next in the sequence will not be assigned.
+ Users may need to retry them again. Failure details possibly with
+ pid will be logged in /sys/fs/resctrl/info/last_cmd_status file.
+
+ 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..df5bd13440b0 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -696,18 +696,41 @@ 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)
+ if (nbytes == 0)
return -EINVAL;
+
+ buf[nbytes - 1] = '\0';
+
rdtgrp = rdtgroup_kn_lock_live(of->kn);
if (!rdtgrp) {
rdtgroup_kn_unlock(of->kn);
return -ENOENT;
}
+
+next:
+ if (!buf || buf[0] == '\0')
+ goto unlock;
+
rdt_last_cmd_clear();

+ pid_str = strim(strsep(&buf, ","));
+
+ if (kstrtoint(pid_str, 0, &pid)) {
+ rdt_last_cmd_printf("Task list parsing error\n");
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ if (pid < 0) {
+ rdt_last_cmd_printf("Invalid pid %d value\n", pid);
+ ret = -EINVAL;
+ goto unlock;
+ }
+
if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED ||
rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
ret = -EINVAL;
@@ -716,6 +739,12 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
}

ret = rdtgroup_move_task(pid, rdtgrp, of);
+ if (ret) {
+ rdt_last_cmd_printf("Error while processing task %d\n", pid);
+ goto unlock;
+ } else {
+ goto next;
+ }

unlock:
rdtgroup_kn_unlock(of->kn);