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

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Date:   Fri, 18 Sep 2020 09:53:25 +0800
From:   Wei Yang <richard.weiyang@...ux.alibaba.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, 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>,
        Vlastimil Babka <vbabka@...e.cz>,
        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 Wed, Sep 16, 2020 at 08:34:08PM +0200, 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>
>---
> 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

__free_one_page() may not merge buddy when its buddy is not available.

Would this comment be a little confusing?

>+ * 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);
> }
> 
> /*
>-- 
>2.26.2

-- 
Wei Yang
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