linux-kernel - Re: [PATCH RFC 1/4] mm/page_alloc: convert "report" flag of __free_one

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Date:   Thu, 24 Sep 2020 12:19:47 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-hyperv@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-acpi@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH RFC 1/4] mm/page_alloc: convert "report" flag of
 __free_one_page() to a proper flag

On 9/16/20 8:34 PM, David Hildenbrand wrote:
> Let's prepare for additional flags and avoid long parameter lists of bools.
> Follow-up patches will also make use of the flags in __free_pages_ok(),
> however, I wasn't able to come up with a better name for the type - should
> be good enough for internal purposes.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Alexander Duyck <alexander.h.duyck@...ux.intel.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Mike Rapoport <rppt@...nel.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/page_alloc.c | 28 ++++++++++++++++++++--------
>  1 file changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6b699d273d6e..91cefb8157dd 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -77,6 +77,18 @@
>  #include "shuffle.h"
>  #include "page_reporting.h"
>  
> +/* Free One Page flags: for internal, non-pcp variants of free_pages(). */
> +typedef int __bitwise fop_t;
> +
> +/* No special request */
> +#define FOP_NONE		((__force fop_t)0)
> +
> +/*
> + * Skip free page reporting notification after buddy merging (will *not* mark
> + * the page reported, only skip the notification).
> + */
> +#define FOP_SKIP_REPORT_NOTIFY	((__force fop_t)BIT(0))
> +
>  /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
>  static DEFINE_MUTEX(pcp_batch_high_lock);
>  #define MIN_PERCPU_PAGELIST_FRACTION	(8)
> @@ -948,10 +960,9 @@ buddy_merge_likely(unsigned long pfn, unsigned long buddy_pfn,
>   * -- nyc
>   */
>  
> -static inline void __free_one_page(struct page *page,
> -		unsigned long pfn,
> -		struct zone *zone, unsigned int order,
> -		int migratetype, bool report)
> +static inline void __free_one_page(struct page *page, unsigned long pfn,
> +				   struct zone *zone, unsigned int order,
> +				   int migratetype, fop_t fop_flags)
>  {
>  	struct capture_control *capc = task_capc(zone);
>  	unsigned long buddy_pfn;
> @@ -1038,7 +1049,7 @@ static inline void __free_one_page(struct page *page,
>  		add_to_free_list(page, zone, order, migratetype);
>  
>  	/* Notify page reporting subsystem of freed page */
> -	if (report)
> +	if (!(fop_flags & FOP_SKIP_REPORT_NOTIFY))
>  		page_reporting_notify_free(order);
>  }
>  
> @@ -1368,7 +1379,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
>  		if (unlikely(isolated_pageblocks))
>  			mt = get_pageblock_migratetype(page);
>  
> -		__free_one_page(page, page_to_pfn(page), zone, 0, mt, true);
> +		__free_one_page(page, page_to_pfn(page), zone, 0, mt, FOP_NONE);
>  		trace_mm_page_pcpu_drain(page, 0, mt);
>  	}
>  	spin_unlock(&zone->lock);
> @@ -1384,7 +1395,7 @@ static void free_one_page(struct zone *zone,
>  		is_migrate_isolate(migratetype))) {
>  		migratetype = get_pfnblock_migratetype(page, pfn);
>  	}
> -	__free_one_page(page, pfn, zone, order, migratetype, true);
> +	__free_one_page(page, pfn, zone, order, migratetype, FOP_NONE);
>  	spin_unlock(&zone->lock);
>  }
>  
> @@ -3277,7 +3288,8 @@ void __putback_isolated_page(struct page *page, unsigned int order, int mt)
>  	lockdep_assert_held(&zone->lock);
>  
>  	/* Return isolated page to tail of freelist. */
> -	__free_one_page(page, page_to_pfn(page), zone, order, mt, false);
> +	__free_one_page(page, page_to_pfn(page), zone, order, mt,
> +			FOP_SKIP_REPORT_NOTIFY);
>  }
>  
>  /*
>