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From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
	linux-sh@vger.kernel.org, x86@kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Wei Yang <richardw.yang@linux.intel.com>
Subject: Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span()
Date: Tue, 4 Feb 2020 10:13:12 +0100
Message-ID: <20200204091312.GC6494@linux> (raw)
In-Reply-To: <20191006085646.5768-9-david@redhat.com>

On Sun, Oct 06, 2019 at 10:56:44AM +0200, David Hildenbrand wrote:
> If we have holes, the holes will automatically get detected and removed
> once we remove the next bigger/smaller section. The extra checks can
> go.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Wei Yang <richardw.yang@linux.intel.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Heh, I have been here before.
I have to confess that when I wrote my version of this I was not really 100%
about removing it, because hotplug was a sort of a "catchall" for all sort of weird
and corner-cases configurations, but thinking more about it, I cannot think of
any situation that would make this blow up.

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
>  mm/memory_hotplug.c | 34 +++++++---------------------------
>  1 file changed, 7 insertions(+), 27 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index f294918f7211..8dafa1ba8d9f 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -393,6 +393,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
>  		if (pfn) {
>  			zone->zone_start_pfn = pfn;
>  			zone->spanned_pages = zone_end_pfn - pfn;
> +		} else {
> +			zone->zone_start_pfn = 0;
> +			zone->spanned_pages = 0;
>  		}
>  	} else if (zone_end_pfn == end_pfn) {
>  		/*
> @@ -405,34 +408,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn,
>  					       start_pfn);
>  		if (pfn)
>  			zone->spanned_pages = pfn - zone_start_pfn + 1;
> +		else {
> +			zone->zone_start_pfn = 0;
> +			zone->spanned_pages = 0;
> +		}
>  	}
> -
> -	/*
> -	 * The section is not biggest or smallest mem_section in the zone, it
> -	 * only creates a hole in the zone. So in this case, we need not
> -	 * change the zone. But perhaps, the zone has only hole data. Thus
> -	 * it check the zone has only hole or not.
> -	 */
> -	pfn = zone_start_pfn;
> -	for (; pfn < zone_end_pfn; pfn += PAGES_PER_SUBSECTION) {
> -		if (unlikely(!pfn_to_online_page(pfn)))
> -			continue;
> -
> -		if (page_zone(pfn_to_page(pfn)) != zone)
> -			continue;
> -
> -		/* Skip range to be removed */
> -		if (pfn >= start_pfn && pfn < end_pfn)
> -			continue;
> -
> -		/* If we find valid section, we have nothing to do */
> -		zone_span_writeunlock(zone);
> -		return;
> -	}
> -
> -	/* The zone has no valid section */
> -	zone->zone_start_pfn = 0;
> -	zone->spanned_pages = 0;
>  	zone_span_writeunlock(zone);
>  }
>  
> -- 
> 2.21.0
> 

-- 
Oscar Salvador
SUSE L3


  reply index

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-06  8:56 [PATCH v6 00/10] mm/memory_hotplug: Shrink zones before removing memory David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 01/10] mm/memunmap: Don't access uninitialized memmap in memunmap_pages() David Hildenbrand
2019-10-06 19:58   ` Damian Tometzki
2019-10-06 20:13     ` David Hildenbrand
2019-10-14  9:05   ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 02/10] mm/memmap_init: Update variable name in memmap_init_zone David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 03/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_pgdat_span() David Hildenbrand
2019-10-14  9:31   ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 04/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_zone_span() David Hildenbrand
2019-10-14  9:32   ` David Hildenbrand
2019-10-14 19:17     ` Andrew Morton
2019-11-19 14:16       ` David Hildenbrand
2019-11-19 20:44         ` Andrew Morton
2019-10-06  8:56 ` [PATCH v6 05/10] mm/memory_hotplug: Shrink zones when offlining memory David Hildenbrand
2019-10-14  9:39   ` David Hildenbrand
2019-10-14 19:16     ` Andrew Morton
2019-10-27 22:45   ` David Hildenbrand
2019-11-30 23:21     ` Andrew Morton
2019-11-30 23:43       ` David Hildenbrand
2019-12-18 17:08       ` David Hildenbrand
2019-12-18 20:16         ` Andrew Morton
2019-12-03 15:10   ` Oscar Salvador
2019-12-03 15:27     ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 06/10] mm/memory_hotplug: Poison memmap in remove_pfn_range_from_zone() David Hildenbrand
2019-10-16 14:01   ` David Hildenbrand
2020-02-04  8:59   ` Oscar Salvador
2019-10-06  8:56 ` [PATCH v6 07/10] mm/memory_hotplug: We always have a zone in find_(smallest|biggest)_section_pfn David Hildenbrand
2020-02-04  9:06   ` Oscar Salvador
2020-02-05  8:57   ` Wei Yang
2020-02-05  8:59     ` David Hildenbrand
2020-02-05  9:26       ` Wei Yang
2019-10-06  8:56 ` [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() David Hildenbrand
2020-02-04  9:13   ` Oscar Salvador [this message]
2020-02-04  9:20     ` David Hildenbrand
2020-02-04 14:25   ` Baoquan He
2020-02-04 14:42     ` David Hildenbrand
2020-02-05 12:43       ` Baoquan He
2020-02-05 13:20         ` David Hildenbrand
2020-02-05 13:34           ` Baoquan He
2020-02-05 13:38             ` David Hildenbrand
2020-02-05 14:12               ` Baoquan He
2020-02-05 14:16                 ` David Hildenbrand
2020-02-05 14:26                   ` Baoquan He
2020-02-05  9:59   ` Wei Yang
2020-02-05 14:48     ` Baoquan He
2020-02-05 22:56       ` Wei Yang
2020-02-05 23:08         ` Baoquan He
2020-02-05 23:26           ` Wei Yang
2020-02-05 23:30             ` Baoquan He
2020-02-05 23:34               ` Wei Yang
2020-02-05 14:54     ` David Laight
2020-02-05 14:55       ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 09/10] mm/memory_hotplug: Drop local variables " David Hildenbrand
2020-02-04  9:26   ` Oscar Salvador
2020-02-04  9:29     ` David Hildenbrand
2020-02-05 10:07   ` Wei Yang
2019-10-06  8:56 ` [PATCH v6 10/10] mm/memory_hotplug: Cleanup __remove_pages() David Hildenbrand
2020-02-04  9:46   ` Oscar Salvador
2020-02-04 12:41     ` David Hildenbrand
2020-02-04 13:13       ` Segher Boessenkool
2020-02-04 13:38         ` David Hildenbrand
2020-02-05 12:51           ` Segher Boessenkool
2020-02-05 13:17             ` David Hildenbrand
2020-02-05 13:18               ` David Hildenbrand
2020-02-05 13:23                 ` David Hildenbrand
2020-02-05 11:48   ` Wei Yang
2019-12-02  9:09 ` [PATCH v6 00/10] mm/memory_hotplug: Shrink zones before removing memory David Hildenbrand
2019-12-03 13:36   ` Oscar Salvador
2020-01-31  4:40     ` Andrew Morton
2020-01-31  9:18       ` David Hildenbrand
2020-01-31 10:03         ` Michal Hocko
2020-01-31 10:36           ` David Hildenbrand
2020-02-04  1:46         ` Andrew Morton
2020-02-04  8:45           ` David Hildenbrand
2020-02-04  9:51             ` Oscar Salvador

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