From: David Hildenbrand <david@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, Michal Hocko <mhocko@kernel.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Oscar Salvador <osalvador@suse.de>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH 6/9] mm, page_alloc: cache pageset high and batch in struct zone
Date: Fri, 25 Sep 2020 12:34:32 +0200 [thread overview]
Message-ID: <be6a28ce-1933-8355-1f9f-44cca6327065@redhat.com> (raw)
In-Reply-To: <20200922143712.12048-7-vbabka@suse.cz>
On 22.09.20 16:37, Vlastimil Babka wrote:
> All per-cpu pagesets for a zone use the same high and batch values, that are
> duplicated there just for performance (locality) reasons. This patch adds the
> same variables also to struct zone as a shared copy.
>
> This will be useful later for making possible to disable pcplists temporarily
> by setting high value to 0, while remembering the values for restoring them
> later. But we can also immediately benefit from not updating pagesets of all
> possible cpus in case the newly recalculated values (after sysctl change or
> memory online/offline) are actually unchanged from the previous ones.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> include/linux/mmzone.h | 6 ++++++
> mm/page_alloc.c | 16 ++++++++++++++--
> 2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 90721f3156bc..7ad3f14dbe88 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -470,6 +470,12 @@ struct zone {
> #endif
> struct pglist_data *zone_pgdat;
> struct per_cpu_pageset __percpu *pageset;
> + /*
> + * the high and batch values are copied to individual pagesets for
> + * faster access
> + */
> + int pageset_high;
> + int pageset_batch;
>
> #ifndef CONFIG_SPARSEMEM
> /*
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index de3b48bda45c..901907799bdc 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5824,6 +5824,8 @@ static void build_zonelists(pg_data_t *pgdat)
> * Other parts of the kernel may not check if the zone is available.
> */
> static void pageset_init(struct per_cpu_pageset *p);
> +#define BOOT_PAGESET_HIGH 0
> +#define BOOT_PAGESET_BATCH 1
Much better. A comment would have been nice ("this disables the pcp via
the boot pageset completely.") :) (I'm pretty sure I'd forget at one
point what these values mean)
> static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
> static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
>
> @@ -6213,8 +6215,8 @@ static void pageset_init(struct per_cpu_pageset *p)
> * need to be as careful as pageset_update() as nobody can access the
> * pageset yet.
> */
> - pcp->high = 0;
> - pcp->batch = 1;
> + pcp->high = BOOT_PAGESET_HIGH;
> + pcp->batch = BOOT_PAGESET_BATCH;
> }
>
> /*
> @@ -6238,6 +6240,14 @@ static void zone_set_pageset_high_and_batch(struct zone *zone)
> new_batch = max(1UL, 1 * new_batch);
> }
>
> + if (zone->pageset_high != new_high ||
> + zone->pageset_batch != new_batch) {
> + zone->pageset_high = new_high;
> + zone->pageset_batch = new_batch;
> + } else {
> + return;
> + }
> +
> for_each_possible_cpu(cpu) {
> p = per_cpu_ptr(zone->pageset, cpu);
> pageset_update(&p->pcp, new_high, new_batch);
> @@ -6300,6 +6310,8 @@ static __meminit void zone_pcp_init(struct zone *zone)
> * offset of a (static) per cpu variable into the per cpu area.
> */
> zone->pageset = &boot_pageset;
> + zone->pageset_high = BOOT_PAGESET_HIGH;
> + zone->pageset_batch = BOOT_PAGESET_BATCH;
I do wonder if copying from any cpuvar inside boot_pageset is cleaner.
zone->pageset_high = &this_cpu_ptr(zone->pageset)->pcp.high;
...
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-09-25 10:34 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 14:37 [PATCH 0/9] disable pcplists during memory offline Vlastimil Babka
2020-09-22 14:37 ` [PATCH 1/9] mm, page_alloc: clean up pageset high and batch update Vlastimil Babka
2020-09-25 10:18 ` David Hildenbrand
2020-10-05 12:03 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 2/9] mm, page_alloc: calculate pageset high and batch once per zone Vlastimil Babka
2020-10-05 12:52 ` Michal Hocko
2020-10-06 22:04 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 3/9] mm, page_alloc: remove setup_pageset() Vlastimil Babka
2020-09-25 10:19 ` David Hildenbrand
2020-10-05 12:59 ` Michal Hocko
2020-10-06 22:11 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 4/9] mm, page_alloc: simplify pageset_update() Vlastimil Babka
2020-09-25 10:23 ` David Hildenbrand
2020-10-05 13:20 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 5/9] mm, page_alloc: make per_cpu_pageset accessible only after init Vlastimil Babka
2020-09-25 10:25 ` David Hildenbrand
2020-10-05 13:24 ` Michal Hocko
2020-10-06 22:28 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 6/9] mm, page_alloc: cache pageset high and batch in struct zone Vlastimil Babka
2020-09-25 10:34 ` David Hildenbrand [this message]
2020-10-06 22:31 ` Vlastimil Babka
2020-10-05 13:28 ` Michal Hocko
2020-10-06 22:34 ` Vlastimil Babka
2020-09-22 14:37 ` [PATCH 7/9] mm, page_alloc: move draining pcplists to page isolation users Vlastimil Babka
2020-09-25 10:39 ` David Hildenbrand
2020-10-05 13:57 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 8/9] mm, page_alloc: drain all pcplists during memory offline Vlastimil Babka
2020-09-25 10:46 ` David Hildenbrand
2020-10-05 14:03 ` Michal Hocko
2020-09-22 14:37 ` [PATCH 9/9] mm, page_alloc: optionally disable pcplists during page isolation Vlastimil Babka
2020-09-25 10:53 ` David Hildenbrand
2020-09-25 10:54 ` David Hildenbrand
2020-09-25 11:10 ` Vlastimil Babka
2020-10-01 8:47 ` David Hildenbrand
2020-10-05 14:05 ` Michal Hocko
2020-10-05 14:22 ` Vlastimil Babka
2020-10-05 16:56 ` Michal Hocko
2020-10-06 8:34 ` Michal Hocko
2020-10-06 8:40 ` David Hildenbrand
2020-10-06 10:05 ` Michal Hocko
2020-09-22 17:15 ` [PATCH 0/9] disable pcplists during memory offline David Hildenbrand
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