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SubjectRe: [PATCH v3 7/7] mm, page_alloc: disable pcplists during memory offline
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On 12.11.20 16:18, Vlastimil Babka wrote:
> On 11/11/20 6:58 PM, David Hildenbrand wrote:
>> On 11.11.20 10:28, Vlastimil Babka wrote:
>>> - /*
>>> - * per-cpu pages are drained after start_isolate_page_range, but
>>> - * if there are still pages that are not free, make sure that we
>>> - * drain again, because when we isolated range we might have
>>> - * raced with another thread that was adding pages to pcp list.
>>> - *
>>> - * Forward progress should be still guaranteed because
>>> - * pages on the pcp list can only belong to MOVABLE_ZONE
>>> - * because has_unmovable_pages explicitly checks for
>>> - * PageBuddy on freed pages on other zones.
>>> - */
>>> ret = test_pages_isolated(start_pfn, end_pfn, MEMORY_OFFLINE);
>>> - if (ret)
>>> - drain_all_pages(zone);
>>> +
>>
>> Why two empty lines before the "} while (ret);" ? (unless I'm confused
>> while looking at this diff)
>>
>
> No there's just a single emply line after "ret = test_pages_isolated..."
> Before there was none, which looked ok with the extra identation of the
> now-removed "drain_all_pages(zone);"
>
>>> +void __zone_set_pageset_high_and_batch(struct zone *zone, unsigned long high,
>>> + unsigned long batch)
>>> +{
>>> + struct per_cpu_pageset *p;
>>> + int cpu;
>>> +
>>> + for_each_possible_cpu(cpu) {
>>> + p = per_cpu_ptr(zone->pageset, cpu);
>>> + pageset_update(&p->pcp, high, batch);
>>> + }
>>> +}
>>> +
>>> /*
>>> * Calculate and set new high and batch values for all per-cpu pagesets of a
>>> * zone, based on the zone's size and the percpu_pagelist_fraction sysctl.
>>> @@ -6315,8 +6338,6 @@ static void pageset_init(struct per_cpu_pageset *p)
>>> static void zone_set_pageset_high_and_batch(struct zone *zone)
>>> {
>>> unsigned long new_high, new_batch;
>>> - struct per_cpu_pageset *p;
>>> - int cpu;
>>>
>>> if (percpu_pagelist_fraction) {
>>> new_high = zone_managed_pages(zone) / percpu_pagelist_fraction;
>>> @@ -6336,10 +6357,7 @@ static void zone_set_pageset_high_and_batch(struct zone *zone)
>>> zone->pageset_high = new_high;
>>> zone->pageset_batch = new_batch;
>>>
>>> - for_each_possible_cpu(cpu) {
>>> - p = per_cpu_ptr(zone->pageset, cpu);
>>> - pageset_update(&p->pcp, new_high, new_batch);
>>> - }
>>> + __zone_set_pageset_high_and_batch(zone, new_high, new_batch);
>>> }
>>
>> These two hunks look like an unrelated cleanup, or am I missing something?
>
> It's extracting part of functionality to __zone_set_pageset_high_and_batch()
> that's now called also from zone_pcp_enable() and zone_pcp_disable() - to only
> adjust the per-cpu zone->pageset values without the usual calculation.
>
>> Thanks for looking into this!
>
> Thanks for review. Here's updated version that adds more detailed comment about
> force_all_cpus parameter to __drain_all_pages() header, hopefully that clarifies
> your concerns.


LGTM!

Reviewed-by: David Hildenbrand <david@redhat.com>


--
Thanks,

David / dhildenb

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