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Subject: [RFC PATCH 2/3] x86/resctrl: Move the task's threads to the group
 automatically
From:   Babu Moger <babu.moger@amd.com>
To:     <fenghua.yu@intel.com>, <reinette.chatre@intel.com>
CC:     <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
        <dave.hansen@linux.intel.com>, <x86@kernel.org>, <hpa@zytor.com>,
        <corbet@lwn.net>, <linux-kernel@vger.kernel.org>,
        <linux-doc@vger.kernel.org>, <eranian@google.com>,
        <peternewman@google.com>
Date:   Tue, 3 Jan 2023 16:06:41 -0600
Message-ID: <167278360189.34228.2442698916556329960.stgit@bmoger-ubuntu>
In-Reply-To: <167278351577.34228.12803395505584557101.stgit@bmoger-ubuntu>
References: <167278351577.34228.12803395505584557101.stgit@bmoger-ubuntu>
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Some micro benchmarks run multiple threads when started. Monitoring=0A=
(or controlling) the benchmark using the task id is bit tricky. Users=0A=
need to track all the threads and assign them individually to monitor=0A=
or control. For example:=0A=
  $stream_lowOverhead -codeAlg 13 -nRep 100000 -cores 0 1 2 3 -memMB 32=0A=
  -alignKB 8192 -aPadB 0 -bPadB 0 -cPadB 0 -testMask 1=0A=
=0A=
  $pidof stream_lowOverhead=0A=
  6793=0A=
=0A=
This benchmark actually runs multiple threads underneath on the cores=0A=
listed above. It can be seen with the command:=0A=
  $ps -T -p 6793=0A=
   PID   SPID TTY          TIME CMD=0A=
  6793   6793 pts/2    00:00:00 stream_lowOverh=0A=
  6793   6802 pts/2    00:01:25 stream_lowOverh=0A=
  6793   6803 pts/2    00:01:25 stream_lowOverh=0A=
  6793   6804 pts/2    00:01:25 stream_lowOverh=0A=
  6793   6805 pts/2    00:01:25 stream_lowOverh=0A=
=0A=
Users need to assign these threads individually to the resctrl group for=0A=
monitoring or controlling.=0A=
=0A=
  $echo 6793 > /sys/fs/restrl/clos1/tasks=0A=
  $echo 6802 > /sys/fs/restrl/clos1/tasks=0A=
  $echo 6803 > /sys/fs/restrl/clos1/tasks=0A=
  $echo 6804 > /sys/fs/restrl/clos1/tasks=0A=
  $echo 6805 > /sys/fs/restrl/clos1/tasks=0A=
=0A=
That is not easy when dealing with numerous threads.=0A=
=0A=
Detect the task's threads automatically and assign them to the resctrl=0A=
group when parent task is assigned. For example:=0A=
  $echo 6793 > /sys/fs/restrl/clos1/tasks=0A=
=0A=
All the threads will be assigned to the group automatically.=0A=
  $cat /sys/fs/restrl/clos1/tasks=0A=
  6793=0A=
  6793=0A=
  6802=0A=
  6803=0A=
  6804=0A=
  6805=0A=
=0A=
Signed-off-by: Babu Moger <babu.moger@amd.com>=0A=
---=0A=
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |    9 ++++++++-=0A=
 1 file changed, 8 insertions(+), 1 deletion(-)=0A=
=0A=
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/r=
esctrl/rdtgroup.c=0A=
index 344607853f4c..0d71ed22cfa9 100644=0A=
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c=0A=
@@ -685,6 +685,7 @@ static int rdtgroup_move_task(pid_t pid, struct rdtgrou=
p *rdtgrp,=0A=
 static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,=0A=
 				    char *buf, size_t nbytes, loff_t off)=0A=
 {=0A=
+	struct task_struct *task, *thread;=0A=
 	struct rdtgroup *rdtgrp;=0A=
 	char *pid_str;=0A=
 	int ret =3D 0;=0A=
@@ -723,7 +724,13 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open=
_file *of,=0A=
 		goto exit;=0A=
 	}=0A=
 =0A=
-	ret =3D rdtgroup_move_task(pid, rdtgrp, of);=0A=
+	task =3D find_task_by_vpid(pid);=0A=
+	thread =3D task;=0A=
+	do {=0A=
+		ret =3D rdtgroup_move_task(thread->pid, rdtgrp, of);=0A=
+		if (ret)=0A=
+			goto exit;=0A=
+	} while_each_thread(task, thread);=0A=
 =0A=
 	goto next;=0A=
 =0A=
=0A=