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Date: Mon, 25 Nov 2019 10:32:16 +0100
From: Michal Hocko <mhocko@...nel.org>
To: Chen Yu <yu.c.chen@...el.com>
Cc: x86@...nel.org, Chen Yu <yu.chen.surf@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Reinette Chatre <reinette.chatre@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>,
Tony Luck <tony.luck@...el.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-api@...r.kernel.org
Subject: Re: [PATCH][v5] x86/resctrl: Add task resctrl information display
[Cc linux-api]
On Mon 25-11-19 12:00:01, Chen Yu wrote:
> Monitoring tools that want to find out which resctrl control
> and monitor groups a task belongs to must currently read
> the "tasks" file in every group until they locate the process
> ID.
>
> Add an additional file /proc/{pid}/resctrl to provide this
> information.
>
> The output is as followed according to Thomas's suggestion,
> for example:
>
> 1) ""
> Resctrl is not available.
>
> 2) "/"
> Task is part of the root group, task is not associated to
> any monitoring group.
>
> 3) "/mon_groups/mon0"
> Task is part of the root group and monitoring group mon0.
>
> 4) "/group0"
> Task is part of control group group0, task is not associated
> to any monitoring group.
>
> 5) "/group0/mon_groups/mon1"
> Task is part of control group group0 and monitoring group mon1.
>
> Tested-by: Jinshi Chen <jinshi.chen@...el.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Alexey Dobriyan <adobriyan@...il.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Reinette Chatre <reinette.chatre@...el.com>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: linux-fsdevel@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> v2: Reduce indentation level in proc_resctrl_show()
> according to Boris's suggestion.
> Create the include/linux/resctrl.h header and
> declare proc_resctrl_show() in this file, so
> that other architectures would probably use it
> in the future. Different architectures should
> implement architectural specific proc_resctrl_show()
> accordingly.
>
> v3: Return empty string if the resctrl filesystem has
> not been mounted per Boris's suggestion.
> Rename the config from CPU_RESCTRL to PROC_CPU_RESCTRL
> to better represent its usage. Move PROC_CPU_RESCTRL
> from arch/Kconfig to fs/proc/Kconfig.
> And let PROC_CPU_RESCTRL to be depended on PROC_FS.
>
> v4: According to Thomas's suggestion, changed the output
> from multiple lines to one single line.
>
> v5: According to Alexey's feedback, removed the header file
> proc_fs.h in resctrl.h, and changed seq_puts() to
> seq_putc() for simplicity.
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 78 ++++++++++++++++++++++++++
> fs/proc/Kconfig | 4 ++
> fs/proc/base.c | 7 +++
> include/linux/resctrl.h | 14 +++++
> 5 files changed, 104 insertions(+)
> create mode 100644 include/linux/resctrl.h
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 8ef85139553f..252364d18887 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -455,6 +455,7 @@ config X86_CPU_RESCTRL
> bool "x86 CPU resource control support"
> depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
> select KERNFS
> + select PROC_CPU_RESCTRL if PROC_FS
> help
> Enable x86 CPU resource control support.
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 2e3b06d6bbc6..f786e7626a65 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -725,6 +725,84 @@ static int rdtgroup_tasks_show(struct kernfs_open_file *of,
> return ret;
> }
>
> +#ifdef CONFIG_PROC_CPU_RESCTRL
> +
> +/*
> + * A task can only be part of one control
> + * group and of one monitoring group which
> + * is associated to that control group.
> + * So one line is simple and clear enough:
> + *
> + * 1) ""
> + * Resctrl is not available.
> + *
> + * 2) "/"
> + * Task is part of the root group, and it is
> + * not associated to any monitoring group.
> + *
> + * 3) "/mon_groups/mon0"
> + * Task is part of the root group and monitoring
> + * group mon0.
> + *
> + * 4) "/group0"
> + * Task is part of control group group0, and it is
> + * not associated to any monitoring group.
> + *
> + * 5) "/group0/mon_groups/mon1"
> + * Task is part of control group group0 and monitoring
> + * group mon1.
> + */
> +int proc_resctrl_show(struct seq_file *s, struct pid_namespace *ns,
> + struct pid *pid, struct task_struct *tsk)
> +{
> + struct rdtgroup *rdtg;
> + int ret = 0;
> +
> + mutex_lock(&rdtgroup_mutex);
> +
> + /* Return empty if resctrl has not been mounted. */
> + if (!static_branch_unlikely(&rdt_enable_key))
> + goto unlock;
> +
> + list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list) {
> + struct rdtgroup *crg;
> +
> + /*
> + * Task information is only relevant for shareable
> + * and exclusive groups.
> + */
> + if (rdtg->mode != RDT_MODE_SHAREABLE &&
> + rdtg->mode != RDT_MODE_EXCLUSIVE)
> + continue;
> +
> + if (rdtg->closid != tsk->closid)
> + continue;
> +
> + seq_printf(s, "/%s", rdtg->kn->name);
> + list_for_each_entry(crg, &rdtg->mon.crdtgrp_list,
> + mon.crdtgrp_list) {
> + if (tsk->rmid != crg->mon.rmid)
> + continue;
> + seq_printf(s, "%smon_groups/%s",
> + rdtg == &rdtgroup_default ? "" : "/",
> + crg->kn->name);
> + break;
> + }
> + seq_putc(s, '\n');
> + goto unlock;
> + }
> + /*
> + * The above search should succeed. Otherwise return
> + * with an error.
> + */
> + ret = -ENOENT;
> +unlock:
> + mutex_unlock(&rdtgroup_mutex);
> +
> + return ret;
> +}
> +#endif
> +
> static int rdt_last_cmd_status_show(struct kernfs_open_file *of,
> struct seq_file *seq, void *v)
> {
> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig
> index cb5629bd5fff..ae96a339d24d 100644
> --- a/fs/proc/Kconfig
> +++ b/fs/proc/Kconfig
> @@ -103,3 +103,7 @@ config PROC_CHILDREN
> config PROC_PID_ARCH_STATUS
> def_bool n
> depends on PROC_FS
> +
> +config PROC_CPU_RESCTRL
> + def_bool n
> + depends on PROC_FS
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index ebea9501afb8..0e4b8bf2b986 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -94,6 +94,7 @@
> #include <linux/sched/debug.h>
> #include <linux/sched/stat.h>
> #include <linux/posix-timers.h>
> +#include <linux/resctrl.h>
> #include <trace/events/oom.h>
> #include "internal.h"
> #include "fd.h"
> @@ -3060,6 +3061,9 @@ static const struct pid_entry tgid_base_stuff[] = {
> #endif
> #ifdef CONFIG_CGROUPS
> ONE("cgroup", S_IRUGO, proc_cgroup_show),
> +#endif
> +#ifdef CONFIG_PROC_CPU_RESCTRL
> + ONE("resctrl", S_IRUGO, proc_resctrl_show),
> #endif
> ONE("oom_score", S_IRUGO, proc_oom_score),
> REG("oom_adj", S_IRUGO|S_IWUSR, proc_oom_adj_operations),
> @@ -3460,6 +3464,9 @@ static const struct pid_entry tid_base_stuff[] = {
> #endif
> #ifdef CONFIG_CGROUPS
> ONE("cgroup", S_IRUGO, proc_cgroup_show),
> +#endif
> +#ifdef CONFIG_PROC_CPU_RESCTRL
> + ONE("resctrl", S_IRUGO, proc_resctrl_show),
> #endif
> ONE("oom_score", S_IRUGO, proc_oom_score),
> REG("oom_adj", S_IRUGO|S_IWUSR, proc_oom_adj_operations),
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> new file mode 100644
> index 000000000000..daf5cf64c6a6
> --- /dev/null
> +++ b/include/linux/resctrl.h
> @@ -0,0 +1,14 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _RESCTRL_H
> +#define _RESCTRL_H
> +
> +#ifdef CONFIG_PROC_CPU_RESCTRL
> +
> +int proc_resctrl_show(struct seq_file *m,
> + struct pid_namespace *ns,
> + struct pid *pid,
> + struct task_struct *tsk);
> +
> +#endif
> +
> +#endif /* _RESCTRL_H */
> --
> 2.17.1
--
Michal Hocko
SUSE Labs
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