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Message-ID: <CAHbLzkruFaKF_92w2qsZz4sH24C-TARXaL-byT6doVVe6VQ4Zg@mail.gmail.com>
Date: Fri, 22 Apr 2022 10:31:56 -0700
From: Yang Shi <shy828301@...il.com>
To: Davidlohr Bueso <dave@...olabs.net>
Cc: linux-mm@...ck.org, mhocko@...nel.org, akpm@...ux-foundation.org,
rientjes@...gle.com, yosryahmed@...gle.com, hannes@...xchg.org,
shakeelb@...gle.com, dave.hansen@...ux.intel.com,
tim.c.chen@...ux.intel.com, roman.gushchin@...ux.dev,
gthelen@...gle.com, a.manzanares@...sung.com,
heekwon.p@...sung.com, gim.jongmin@...sung.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] mm/migration: export demotion_path of a node via sysfs
On Fri, Apr 15, 2022 at 10:39 PM Davidlohr Bueso <dave@...olabs.net> wrote:
>
> Add a /sys/devices/system/node/nodeX/demotion_path file
> to export the possible target(s) in node_demotion[node].
I'm not sure if you noticed that Jagdish Gediya is working on the
similar patch, please see
https://lore.kernel.org/linux-mm/20220413092206.73974-1-jvgediya@linux.ibm.com/
It would be better to combine the two to avoid duplicate effort.
>
> Signed-off-by: Davidlohr Bueso <dave@...olabs.net>
> ---
> Documentation/ABI/stable/sysfs-devices-node | 6 ++++
> drivers/base/node.c | 39 +++++++++++++++++++++
> include/linux/migrate.h | 15 ++++++++
> mm/migrate.c | 15 +-------
> 4 files changed, 61 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node
> index 3c935e1334f7..f620c6ae013c 100644
> --- a/Documentation/ABI/stable/sysfs-devices-node
> +++ b/Documentation/ABI/stable/sysfs-devices-node
> @@ -192,3 +192,9 @@ Description:
> When it completes successfully, the specified amount or more memory
> will have been reclaimed, and -EAGAIN if less bytes are reclaimed
> than the specified amount.
> +
> +What: /sys/devices/system/node/nodeX/demotion_path
> +Date: April 2022
> +Contact: Davidlohr Bueso <dave@...olabs.net>
> +Description:
> + Shows nodes within the next tier of slower memory below this node.
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index d80c478e2a6e..ab4bae777535 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -17,6 +17,7 @@
> #include <linux/nodemask.h>
> #include <linux/cpu.h>
> #include <linux/device.h>
> +#include <linux/migrate.h>
> #include <linux/pm_runtime.h>
> #include <linux/swap.h>
> #include <linux/slab.h>
> @@ -560,11 +561,49 @@ static ssize_t node_read_distance(struct device *dev,
> }
> static DEVICE_ATTR(distance, 0444, node_read_distance, NULL);
>
> +static ssize_t node_read_demotion_path(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int nid = dev->id;
> + int len = 0;
> + int i;
> + struct demotion_nodes *nd;
> +
> + /*
> + * buf is currently PAGE_SIZE in length and each node needs 4 chars
> + * at the most (target + space or newline).
> + */
> + BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
> +
> + if (!node_demotion) {
> + len += sysfs_emit_at(buf, len, "%d", NUMA_NO_NODE);
> + goto done;
> + }
> +
> + nd = &node_demotion[nid];
> +
> + rcu_read_lock();
> + if (nd->nr == 0)
> + len += sysfs_emit_at(buf, len, "%d", NUMA_NO_NODE);
> + else {
> + for (i = 0; i < nd->nr; i++) {
> + len += sysfs_emit_at(buf, len, "%s%d",
> + i ? " " : "", nd->nodes[i]);
> + }
> + }
> + rcu_read_unlock();
> +done:
> + len += sysfs_emit_at(buf, len, "\n");
> + return len;
> +}
> +static DEVICE_ATTR(demotion_path, 0444, node_read_demotion_path, NULL);
> +
> static struct attribute *node_dev_attrs[] = {
> &dev_attr_meminfo.attr,
> &dev_attr_numastat.attr,
> &dev_attr_distance.attr,
> &dev_attr_vmstat.attr,
> + &dev_attr_demotion_path.attr,
> NULL
> };
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 90e75d5a54d6..b0ac6a717e44 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -111,6 +111,21 @@ static inline int migrate_misplaced_page(struct page *page,
> }
> #endif /* CONFIG_NUMA_BALANCING */
>
> +#define DEFAULT_DEMOTION_TARGET_NODES 15
> +
> +#if MAX_NUMNODES < DEFAULT_DEMOTION_TARGET_NODES
> +#define DEMOTION_TARGET_NODES (MAX_NUMNODES - 1)
> +#else
> +#define DEMOTION_TARGET_NODES DEFAULT_DEMOTION_TARGET_NODES
> +#endif
> +
> +struct demotion_nodes {
> + unsigned short nr;
> + short nodes[DEMOTION_TARGET_NODES];
> +};
> +
> +extern struct demotion_nodes *node_demotion __read_mostly;
> +
> #ifdef CONFIG_MIGRATION
>
> /*
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 6c31ee1e1c9b..e47ea25fcfe8 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2172,20 +2172,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
> * must be held over all reads to ensure that no cycles are
> * observed.
> */
> -#define DEFAULT_DEMOTION_TARGET_NODES 15
> -
> -#if MAX_NUMNODES < DEFAULT_DEMOTION_TARGET_NODES
> -#define DEMOTION_TARGET_NODES (MAX_NUMNODES - 1)
> -#else
> -#define DEMOTION_TARGET_NODES DEFAULT_DEMOTION_TARGET_NODES
> -#endif
> -
> -struct demotion_nodes {
> - unsigned short nr;
> - short nodes[DEMOTION_TARGET_NODES];
> -};
> -
> -static struct demotion_nodes *node_demotion __read_mostly;
> +struct demotion_nodes *node_demotion __read_mostly;
>
> /**
> * next_demotion_node() - Get the next node in the demotion path
> --
> 2.26.2
>
>
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