Re: [PATCH 01/27] mm, vmstat: Add infrastructure for per-node vmstats

Vlastimil Babka
2016-06-10T13:32:01Z

On 06/09/2016 08:04 PM, Mel Gorman wrote:
> References: bnc#969297 PM performance -- intel_pstate
> Patch-mainline: No, expected 4.7 and queued in linux-mm
> Patch-name: patches.suse/mm-vmstat-Add-infrastructure-for-per-node-vmstats.patch

Remove?

> VM statistic counters for reclaim decisions are zone-based. If the kernel
> is to reclaim on a per-node basis then we need to track per-node statistics
> but there is no infrastructure for that. The most notable change is that
> the old node_page_state is renamed to sum_zone_node_page_state. The new
> node_page_state takes a pglist_data and uses per-node stats but none exist
> yet. There is some renaming such as vm_stat to vm_zone_stat and the addition
> of vm_node_stat and the renaming of mod_state to mod_zone_state. Otherwise,
> this is mostly a mechanical patch with no functional change. There is a
> lot of similarity between the node and zone helpers which is unfortunate
> but there was no obvious way of reusing the code and maintaining type safety.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Mel Gorman <mgorman@suse.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

Some nitpicks below.

> @@ -237,12 +286,26 @@ static inline void __inc_zone_page_state(struct page *page,
> __inc_zone_state(page_zone(page), item);
> }
>
> +static inline void __inc_node_page_state(struct page *page,
> + enum node_stat_item item)
> +{
> + __inc_node_state(page_zone(page)->zone_pgdat, item);

This page -> node translation looks needlessly ineffective. How about
using NODE_DATA(page_to_nid(page)).

> +}
> +
> +
> static inline void __dec_zone_page_state(struct page *page,
> enum zone_stat_item item)
> {
> __dec_zone_state(page_zone(page), item);
> }
>
> +static inline void __dec_node_page_state(struct page *page,
> + enum node_stat_item item)
> +{
> + __dec_node_state(page_zone(page)->zone_pgdat, item);
> +}

Ditto.

> @@ -188,9 +190,13 @@ void refresh_zone_stat_thresholds(void)
>
> threshold = calculate_normal_threshold(zone);
>
> - for_each_online_cpu(cpu)
> + for_each_online_cpu(cpu) {
> + struct pglist_data *pgdat = zone->zone_pgdat;

Move the variable outside?

> per_cpu_ptr(zone->pageset, cpu)->stat_threshold
> = threshold;
> + per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold
> + = threshold;
> + }
>
> /*
> * Only set percpu_drift_mark if there is a danger that
> void __inc_zone_page_state(struct page *page, enum zone_stat_item item)

[...]

> {
> __inc_zone_state(page_zone(page), item);
> }
> EXPORT_SYMBOL(__inc_zone_page_state);
>
> +void __inc_node_page_state(struct page *page, enum node_stat_item item)
> +{
> + __inc_node_state(page_zone(page)->zone_pgdat, item);

Same page -> node thing here.

> +void __dec_node_page_state(struct page *page, enum node_stat_item item)
> +{
> + __dec_node_state(page_zone(page)->zone_pgdat, item);

And here.

>
> void dec_zone_page_state(struct page *page, enum zone_stat_item item)
> {
> - mod_state(page_zone(page), item, -1, -1);
> + mod_zone_state(page_zone(page), item, -1, -1);
> }
> EXPORT_SYMBOL(dec_zone_page_state);
> +
> +static inline void mod_node_state(struct pglist_data *pgdat,
> + enum node_stat_item item, int delta, int overstep_mode)
> +{
> + struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
> + s8 __percpu *p = pcp->vm_node_stat_diff + item;
> + long o, n, t, z;
> +
> + do {
> + z = 0; /* overflow to zone counters */

s/zone/node/?

> +
> + /*
> + * The fetching of the stat_threshold is racy. We may apply
> + * a counter threshold to the wrong the cpu if we get
> + * rescheduled while executing here. However, the next
> + * counter update will apply the threshold again and
> + * therefore bring the counter under the threshold again.
> + *
> + * Most of the time the thresholds are the same anyways
> + * for all cpus in a zone.

same here.

> + */
> + t = this_cpu_read(pcp->stat_threshold);
> +
> + o = this_cpu_read(*p);
> + n = delta + o;
> +
> + if (n > t || n < -t) {
> + int os = overstep_mode * (t >> 1) ;
> +
> + /* Overflow must be added to zone counters */

and here.

> +}
> +
> +void inc_node_page_state(struct page *page, enum node_stat_item item)
> +{
> + mod_node_state(page_zone(page)->zone_pgdat, item, 1, 1);

Ditto about page -> nid.

> +}
> +EXPORT_SYMBOL(inc_node_page_state);
> +
> +void dec_node_page_state(struct page *page, enum node_stat_item item)
> +{
> + mod_node_state(page_zone(page)->zone_pgdat, item, -1, -1);
> +}

Ditto.

> +EXPORT_SYMBOL(dec_node_page_state);
> #else
> /*
> * Use interrupt disable to serialize counter updates
> @@ -436,21 +568,69 @@ void dec_zone_page_state(struct page *page, enum zone_stat_item item)
> local_irq_restore(flags);
> }
> EXPORT_SYMBOL(dec_zone_page_state);
> -#endif
>
> +void inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
> +{
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + __inc_node_state(pgdat, item);
> + local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL(inc_node_state);
> +
> +void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
> + long delta)
> +{
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + __mod_node_page_state(pgdat, item, delta);
> + local_irq_restore(flags);
> +}
> +EXPORT_SYMBOL(mod_node_page_state);
> +
> +void inc_node_page_state(struct page *page, enum node_stat_item item)
> +{
> + unsigned long flags;
> + struct pglist_data *pgdat;
> +
> + pgdat = page_zone(page)->zone_pgdat;

And here.

,9 +736,11 @@ static int refresh_cpu_vm_stats(bool do_pagesets)
> */
> void cpu_vm_stats_fold(int cpu)
> {
> + struct pglist_data *pgdat;
> struct zone *zone;
> int i;
> - int global_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
> + int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
> + int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };
>
> for_each_populated_zone(zone) {
> struct per_cpu_pageset *p;
> @@ -555,11 +754,27 @@ void cpu_vm_stats_fold(int cpu)
> v = p->vm_stat_diff[i];
> p->vm_stat_diff[i] = 0;
> atomic_long_add(v, &zone->vm_stat[i]);
> - global_diff[i] += v;
> + global_zone_diff[i] += v;
> }
> }
>