On Thu, May 12, 2022 at 12:36 AM Aneesh Kumar K.V
<aneesh.kumar@xxxxxxxxxxxxx> wrote:
>
> Wei Xu <weixugc@xxxxxxxxxx> writes:
>
> > On Thu, May 12, 2022 at 12:12 AM Aneesh Kumar K V
> > <aneesh.kumar@xxxxxxxxxxxxx> wrote:
> >>
> >> On 5/12/22 12:33 PM, ying.huang@xxxxxxxxx wrote:
> >> > On Wed, 2022-05-11 at 23:22 -0700, Wei Xu wrote:
> >> >> Sysfs Interfaces
> >> >> ================
> >> >>
> >> >> * /sys/devices/system/memtier/memtierN/nodelist
> >> >>
> >> >> where N = 0, 1, 2 (the kernel supports only 3 tiers for now).
> >> >>
> >> >> Format: node_list
> >> >>
> >> >> Read-only. When read, list the memory nodes in the specified tier.
> >> >>
> >> >> Tier 0 is the highest tier, while tier 2 is the lowest tier.
> >> >>
> >> >> The absolute value of a tier id number has no specific meaning.
> >> >> What matters is the relative order of the tier id numbers.
> >> >>
> >> >> When a memory tier has no nodes, the kernel can hide its memtier
> >> >> sysfs files.
> >> >>
> >> >> * /sys/devices/system/node/nodeN/memtier
> >> >>
> >> >> where N = 0, 1, ...
> >> >>
> >> >> Format: int or empty
> >> >>
> >> >> When read, list the memory tier that the node belongs to. Its value
> >> >> is empty for a CPU-only NUMA node.
> >> >>
> >> >> When written, the kernel moves the node into the specified memory
> >> >> tier if the move is allowed. The tier assignment of all other nodes
> >> >> are not affected.
> >> >>
> >> >> Initially, we can make this interface read-only.
> >> >
> >> > It seems that "/sys/devices/system/node/nodeN/memtier" has all
> >> > information we needed. Do we really need
> >> > "/sys/devices/system/memtier/memtierN/nodelist"?
> >> >
> >> > That can be gotten via a simple shell command line,
> >> >
> >> > $ grep . /sys/devices/system/node/nodeN/memtier | sort -n -k 2 -t ':'
> >> >
> >>
> >> It will be really useful to fetch the memory tier node list in an easy
> >> fashion rather than reading multiple sysfs directories. If we don't have
> >> other attributes for memorytier, we could keep
> >> "/sys/devices/system/memtier/memtierN" a NUMA node list there by
> >> avoiding /sys/devices/system/memtier/memtierN/nodelist
> >>
> >> -aneesh
> >
> > It is harder to implement memtierN as just a file and doesn't follow
> > the existing sysfs pattern, either. Besides, it is extensible to have
> > memtierN as a directory.
>
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 6248326f944d..251f38ec3816 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -1097,12 +1097,49 @@ static struct attribute *node_state_attrs[] = {
> NULL
> };
>
> +#define MAX_TIER 3
> +nodemask_t memory_tier[MAX_TIER];
> +
> +#define _TIER_ATTR_RO(name, tier_index) \
> + { __ATTR(name, 0444, show_tier, NULL), tier_index, NULL }
> +
> +struct memory_tier_attr {
> + struct device_attribute attr;
> + int tier_index;
> + int (*write)(nodemask_t nodes);
> +};
> +
> +static ssize_t show_tier(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct memory_tier_attr *mt = container_of(attr, struct memory_tier_attr, attr);
> +
> + return sysfs_emit(buf, "%*pbl\n",
> + nodemask_pr_args(&memory_tier[mt->tier_index]));
> +}
> +
> static const struct attribute_group memory_root_attr_group = {
> .attrs = node_state_attrs,
> };
>
> +
> +#define TOP_TIER 0
> +static struct memory_tier_attr memory_tiers[] = {
> + [0] = _TIER_ATTR_RO(memory_top_tier, TOP_TIER),
> +};
> +
> +static struct attribute *memory_tier_attrs[] = {
> + &memory_tiers[0].attr.attr,
> + NULL
> +};
> +
> +static const struct attribute_group memory_tier_attr_group = {
> + .attrs = memory_tier_attrs,
> +};
> +
> static const struct attribute_group *cpu_root_attr_groups[] = {
> &memory_root_attr_group,
> + &memory_tier_attr_group,
> NULL,
> };
>
>
> As long as we have the ability to see the nodelist, I am good with the
> proposal.
>
> -aneesh
I am OK with moving back the memory tier nodelist into node/. When
there are more memory tier attributes needed, we can then create the
memory tier subtree and replace the tier nodelist in node/ with
symlinks.
So the revised sysfs interfaces are:
* /sys/devices/system/node/memory_tierN (read-only)
where N = 0, 1, 2
Format: node_list
* /sys/devices/system/node/nodeN/memory_tier (read/write)
where N = 0, 1, ...
Format: int or empty
