mm/migrate: add sysfs interface to enable reclaim migration

Some method is obviously needed to enable reclaim-based migration.

Just like traditional autonuma, there will be some workloads that will
benefit like workloads with more "static" configurations where hot pages
stay hot and cold pages stay cold.  If pages come and go from the hot and
cold sets, the benefits of this approach will be more limited.

The benefits are truly workload-based and *not* hardware-based.  We do not
believe that there is a viable threshold where certain hardware
configurations should have this mechanism enabled while others do not.

To be conservative, earlier work defaulted to disable reclaim- based
migration and did not include a mechanism to enable it.  This proposes add
a new sysfs file

  /sys/kernel/mm/numa/demotion_enabled

as a method to enable it.

We are open to any alternative that allows end users to enable this
mechanism or disable it if workload harm is detected (just like
traditional autonuma).

Once this is enabled page demotion may move data to a NUMA node that does
not fall into the cpuset of the allocating process.  This could be
construed to violate the guarantees of cpusets.  However, since this is an
opt-in mechanism, the assumption is that anyone enabling it is content to
relax the guarantees.

Link: https://lkml.kernel.org/r/20210721063926.3024591-9-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-10-ying.huang@intel.com
Signed-off-by: Huang Ying <ying.huang@intel.com>
Originally-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Huang Ying 2021-09-02 14:59:33 -07:00 committed by Linus Torvalds
parent 3a235693d3
commit 20b51af15e
4 changed files with 92 additions and 2 deletions

View File

@ -0,0 +1,24 @@
What: /sys/kernel/mm/numa/
Date: June 2021
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Interface for NUMA
What: /sys/kernel/mm/numa/demotion_enabled
Date: June 2021
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Enable/disable demoting pages during reclaim
Page migration during reclaim is intended for systems
with tiered memory configurations. These systems have
multiple types of memory with varied performance
characteristics instead of plain NUMA systems where
the same kind of memory is found at varied distances.
Allowing page migration during reclaim enables these
systems to migrate pages from fast tiers to slow tiers
when the fast tier is under pressure. This migration
is performed before swap. It may move data to a NUMA
node that does not fall into the cpuset of the
allocating process which might be construed to violate
the guarantees of cpusets. This should not be enabled
on systems which need strict cpuset location
guarantees.

View File

@ -184,6 +184,8 @@ extern bool vma_migratable(struct vm_area_struct *vma);
extern int mpol_misplaced(struct page *, struct vm_area_struct *, unsigned long);
extern void mpol_put_task_policy(struct task_struct *);
extern bool numa_demotion_enabled;
#else
struct mempolicy {};
@ -292,5 +294,7 @@ static inline nodemask_t *policy_nodemask_current(gfp_t gfp)
{
return NULL;
}
#define numa_demotion_enabled false
#endif /* CONFIG_NUMA */
#endif

View File

@ -3021,3 +3021,64 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
p += scnprintf(p, buffer + maxlen - p, ":%*pbl",
nodemask_pr_args(&nodes));
}
bool numa_demotion_enabled = false;
#ifdef CONFIG_SYSFS
static ssize_t numa_demotion_enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%s\n",
numa_demotion_enabled? "true" : "false");
}
static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
numa_demotion_enabled = true;
else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
numa_demotion_enabled = false;
else
return -EINVAL;
return count;
}
static struct kobj_attribute numa_demotion_enabled_attr =
__ATTR(demotion_enabled, 0644, numa_demotion_enabled_show,
numa_demotion_enabled_store);
static struct attribute *numa_attrs[] = {
&numa_demotion_enabled_attr.attr,
NULL,
};
static const struct attribute_group numa_attr_group = {
.attrs = numa_attrs,
};
static int __init numa_init_sysfs(void)
{
int err;
struct kobject *numa_kobj;
numa_kobj = kobject_create_and_add("numa", mm_kobj);
if (!numa_kobj) {
pr_err("failed to create numa kobject\n");
return -ENOMEM;
}
err = sysfs_create_group(numa_kobj, &numa_attr_group);
if (err) {
pr_err("failed to register numa group\n");
goto delete_obj;
}
return 0;
delete_obj:
kobject_put(numa_kobj);
return err;
}
subsys_initcall(numa_init_sysfs);
#endif

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@ -524,6 +524,8 @@ static long add_nr_deferred(long nr, struct shrinker *shrinker,
static bool can_demote(int nid, struct scan_control *sc)
{
if (!numa_demotion_enabled)
return false;
if (sc) {
if (sc->no_demotion)
return false;
@ -534,8 +536,7 @@ static bool can_demote(int nid, struct scan_control *sc)
if (next_demotion_node(nid) == NUMA_NO_NODE)
return false;
// FIXME: actually enable this later in the series
return false;
return true;
}
static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,