Re: [RFC] proc: Add a new isolated /proc/pid/mempolicy type.

From: Michal Hocko
Date: Mon Sep 26 2022 - 05:57:05 EST

Next message: Geert Uytterhoeven: "Re: [PATCH v3 1/3] m68k: process bootinfo records before saving them"
Previous message: Uwe Kleine-König: "Re: [PATCH v2 2/9] pwm: lpss: Move exported symbols to PWM_LPSS namespace"
In reply to: hezhongkun: "[RFC] proc: Add a new isolated /proc/pid/mempolicy type."
Next in thread: Zhongkun He: "Re: [External] Re: [RFC] proc: Add a new isolated /proc/pid/mempolicy type."
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

[Cc linux-api - please do so for any patches making/updating
kernel<->user interfaces]

On Mon 26-09-22 17:10:33, hezhongkun wrote:
> From: Zhongkun He <hezhongkun.hzk@xxxxxxxxxxxxx>
>
> /proc/pid/mempolicy can be used to check and adjust the userspace task's
> mempolicy dynamically.In many case, the application and the control plane
> are two separate systems. When the application is created, it doesn't know
> how to use memory, and it doesn't care. The control plane will decide the
> memory usage policy based on different reasons.In that case, we can
> dynamically adjust the mempolicy using /proc/pid/mempolicy interface.

Is there any reason to make it procfs interface rather than pidfd one?

[keeping the rest of the email for the linux-api reference]

> Format of input:
> ----------------
> <mode>[=<flags>][:<nodelist>]
>
> Example
> -------
> set mempolicy:
> $ echo "interleave=static:0-3" > /proc/27036/mempolicy
> $ cat /proc/27036/mempolicy
> interleave=static:0-3
> remove mempolicy:
> + $ echo "default" > /proc/27036/mempolicy
>
> The following 6 mempolicy mode types：
> "default" "prefer" "bind" "interleave" "local" "prefer (many)"
>
> The supported mode flags are:
> "static" "relative"
>
> nodelist For example：0-3 or 0,1,2,3
>
> Signed-off-by: Zhongkun He <hezhongkun.hzk@xxxxxxxxxxxxx>
> ---
> Documentation/filesystems/proc.rst | 40 +++++++++
> fs/proc/base.c | 2 +
> fs/proc/internal.h | 1 +
> fs/proc/task_mmu.c | 129 +++++++++++++++++++++++++++++
> include/linux/mempolicy.h | 5 --
> mm/mempolicy.c | 2 -
> 6 files changed, 172 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index e7aafc82be99..fa7bc24c6a91 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -47,6 +47,8 @@ fixes/update part 1.1 Stefani Seibold <stefani@xxxxxxxxxxx> June 9 2009
> 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
> 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
> 3.12 /proc/<pid>/arch_status - Task architecture specific information
> + 3.13 /proc/<pid>/mempolicy & /proc/<pid>/task/<tid>/mempolicy- Adjust
> + the mempolicy
>
> 4 Configuring procfs
> 4.1 Mount options
> @@ -2145,6 +2147,44 @@ AVX512_elapsed_ms
> the task is unlikely an AVX512 user, but depends on the workload and the
> scheduling scenario, it also could be a false negative mentioned above.
>
> +3.13 /proc/<pid>/mempolicy & /proc/<pid>/task/<tid>/mempolicy- Adjust the mempolicy
> +-----------------------------------------------------------------------------------
> +When CONFIG_NUMA is enabled, these files can be used to check and adjust the current
> +mempolicy.Please note that the effectively <pid>,<tid> is from userspace programs.
> +
> +Format of input:
> +----------------
> +<mode>[=<flags>][:<nodelist>]
> +
> +Example
> +-------
> +set mempolicy:
> + $ echo "interleave=static:0-3" > /proc/27036/mempolicy
> + $ cat /proc/27036/mempolicy
> + interleave=static:0-3
> +
> +remove mempolicy:
> + $ echo "default" > /proc/27036/mempolicy
> +
> +The following 6 mempolicy mode types are supported:
> +"default" Default is converted to the NULL memory policy, any existing non-default policy
> + will simply be removed when "default" is specified.
> +"prefer" The allocation should be attempted from the single node specified in the policy.
> +"bind" Memory must come from the set of nodes specified by the policy.
> +"interleave" Page allocations be interleaved across the nodes specified in the policy.
> +"local" The memory is allocated on the node of the CPU that triggered the allocation.
> +"prefer (many)" The allocation should be preferrably satisfied from the nodemask specified in the policy.
> +
> +The supported mode flags are:
> +
> +"static" A nonempty nodemask specifies physical node IDs.
> +"relative" A nonempty nodemask specifies node IDs that are relative
> + to the set of node IDs allowed by the thread's current cpuset.
> +
> +nodelist For example: 0-3 or 0,1,2,3
> +
> +Please see: Documentation/admin-guide/mm/numa_memory_policy.rst for descriptions of memory policy.
> +
> Chapter 4: Configuring procfs
> =============================
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 93f7e3d971e4..4dbe714b4e61 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -3252,6 +3252,7 @@ static const struct pid_entry tgid_base_stuff[] = {
> REG("maps", S_IRUGO, proc_pid_maps_operations),
> #ifdef CONFIG_NUMA
> REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
> + REG("mempolicy", S_IRUGO|S_IWUSR, proc_mempolicy_operations),
> #endif
> REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations),
> LNK("cwd", proc_cwd_link),
> @@ -3600,6 +3601,7 @@ static const struct pid_entry tid_base_stuff[] = {
> #endif
> #ifdef CONFIG_NUMA
> REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
> + REG("mempolicy", S_IRUGO|S_IWUSR, proc_mempolicy_operations),
> #endif
> REG("mem", S_IRUSR|S_IWUSR, proc_mem_operations),
> LNK("cwd", proc_cwd_link),
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 06a80f78433d..33ffbd79db58 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -300,6 +300,7 @@ extern const struct file_operations proc_pid_smaps_operations;
> extern const struct file_operations proc_pid_smaps_rollup_operations;
> extern const struct file_operations proc_clear_refs_operations;
> extern const struct file_operations proc_pagemap_operations;
> +extern const struct file_operations proc_mempolicy_operations;
>
> extern unsigned long task_vsize(struct mm_struct *);
> extern unsigned long task_statm(struct mm_struct *,
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 4e0023643f8b..299276e19c52 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -2003,4 +2003,133 @@ const struct file_operations proc_pid_numa_maps_operations = {
> .release = proc_map_release,
> };
>
> +#define MPOLBUFLEN 64
> +/*
> + *Display task's memory policy via /proc./
> + */
> +static ssize_t mempolicy_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct task_struct *task = get_proc_task(file_inode(file));
> + char buffer[MPOLBUFLEN];
> + struct mempolicy *mpol;
> + size_t len = 0;
> +
> + if (!task)
> + return -ESRCH;
> +
> + task_lock(task);
> + mpol = task->mempolicy;
> + mpol_get(mpol);
> + task_unlock(task);
> +
> + if (!mpol || mpol->mode == MPOL_DEFAULT)
> + goto out;
> +
> + memset(buffer, 0, sizeof(buffer));
> + mpol_to_str(buffer, sizeof(buffer), mpol);
> + buffer[strlen(buffer)] = '\n';
> + len = simple_read_from_buffer(buf, count, ppos, buffer, strlen(buffer));
> +
> +out:
> + mpol_put(mpol);
> + put_task_struct(task);
> + return len;
> +}
> +
> +/*
> + *Update nodemask of mempolicy according to task->mems_allowed.
> + */
> +static int update_task_mpol(struct task_struct *task, struct mempolicy *mpol)
> +{
> + nodemask_t tsk_allowed;
> + struct mempolicy *old = NULL;
> + int err = 0;
> +
> + task_lock(task);
> + local_irq_disable();
> + old = task->mempolicy;
> +
> + if (mpol)
> + nodes_and(tsk_allowed, task->mems_allowed, mpol->w.user_nodemask);
> + else
> + nodes_clear(tsk_allowed);
> +
> + if (!nodes_empty(tsk_allowed)) {
> + task->mempolicy = mpol;
> + mpol_rebind_task(task, &tsk_allowed);
> + } else if (!mpol || mpol->mode == MPOL_LOCAL) {
> + /*default (pol==NULL), clear the old mpol;
> + *local memory policies are not a subject of any remapping.
> + */
> + task->mempolicy = mpol;
> + } else {
> + /*tsk_allowed is empty.*/
> + err = -EINVAL;
> + }
> +
> + if (!err && mpol && mpol->mode == MPOL_INTERLEAVE)
> + task->il_prev = MAX_NUMNODES-1;
> +
> + local_irq_enable();
> + task_unlock(task);
> +
> + /*If successful, release old policy,
> + * otherwise keep old and release mpol.
> + */
> + if (err)
> + mpol_put(mpol);
> + else
> + mpol_put(old);
> +
> + return err;
> +}
> +
> +/*
> + *Modify task's memory policy via /proc.
> + */
> +static ssize_t mempolicy_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + char buffer[MPOLBUFLEN];
> + struct mempolicy *mpol = NULL;
> + struct task_struct *task;
> + int err = 0;
> +
> + task = get_proc_task(file_inode(file));
> +
> + if (!task)
> + return -ESRCH;
> +
> + /*we can only change the user's mempolicy*/
> + if (task->flags & PF_KTHREAD || is_global_init(task)) {
> + err = -EPERM;
> + goto out;
> + }
> +
> + memset(buffer, 0, sizeof(buffer));
> + if (count > sizeof(buffer) - 1)
> + count = sizeof(buffer) - 1;
> + if (copy_from_user(buffer, buf, count)) {
> + err = -EFAULT;
> + goto out;
> + }
> +
> + err = mpol_parse_str(strstrip(buffer), &mpol);
> + if (err) {
> + err = -EINVAL;
> + goto out;
> + }
> + err = update_task_mpol(task, mpol);
> +out:
> + put_task_struct(task);
> + return err < 0 ? err : count;
> +}
> +
> +const struct file_operations proc_mempolicy_operations = {
> + .read = mempolicy_read,
> + .write = mempolicy_write,
> + .llseek = default_llseek,
> +};
> +
> #endif /* CONFIG_NUMA */
> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
> index 668389b4b53d..a08f66972e6b 100644
> --- a/include/linux/mempolicy.h
> +++ b/include/linux/mempolicy.h
> @@ -172,10 +172,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
> const nodemask_t *to, int flags);
>
>
> -#ifdef CONFIG_TMPFS
> extern int mpol_parse_str(char *str, struct mempolicy **mpol);
> -#endif
> -
> extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
>
> /* Check if a vma is migratable */
> @@ -277,12 +274,10 @@ static inline void check_highest_zone(int k)
> {
> }
>
> -#ifdef CONFIG_TMPFS
> static inline int mpol_parse_str(char *str, struct mempolicy **mpol)
> {
> return 1; /* error */
> }
> -#endif
>
> static inline int mpol_misplaced(struct page *page, struct vm_area_struct *vma,
> unsigned long address)
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index b73d3248d976..a1ae6412e3ae 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2958,7 +2958,6 @@ static const char * const policy_modes[] =
> };
>
>
> -#ifdef CONFIG_TMPFS
> /**
> * mpol_parse_str - parse string to mempolicy, for tmpfs mpol mount option.
> * @str: string containing mempolicy to parse
> @@ -3091,7 +3090,6 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
> *mpol = new;
> return err;
> }
> -#endif /* CONFIG_TMPFS */
>
> /**
> * mpol_to_str - format a mempolicy structure for printing
> --
> 2.25.1

--
Michal Hocko
SUSE Labs

Next message: Geert Uytterhoeven: "Re: [PATCH v3 1/3] m68k: process bootinfo records before saving them"
Previous message: Uwe Kleine-König: "Re: [PATCH v2 2/9] pwm: lpss: Move exported symbols to PWM_LPSS namespace"
In reply to: hezhongkun: "[RFC] proc: Add a new isolated /proc/pid/mempolicy type."
Next in thread: Zhongkun He: "Re: [External] Re: [RFC] proc: Add a new isolated /proc/pid/mempolicy type."
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]