Commit dbbee9d5 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm/page_alloc: convert per-cpu list protection to local_lock 

There is a lack of clarity of what exactly
local_irq_save/local_irq_restore protects in page_alloc.c .  It conflates
the protection of per-cpu page allocation structures with per-cpu vmstat
deltas.

This patch protects the PCP structure using local_lock which for most
configurations is identical to IRQ enabling/disabling.  The scope of the
lock is still wider than it should be but this is decreased later.

It is possible for the local_lock to be embedded safely within struct
per_cpu_pages but it adds complexity to free_unref_page_list.

[akpm@linux-foundation.org: coding style fixes]
[mgorman@techsingularity.net: work around a pahole limitation with zero-sized struct pagesets]
  Link: https://lkml.kernel.org/r/20210526080741.GW30378@techsingularity.net
[lkp@intel.com: Make pagesets static]

Link: https://lkml.kernel.org/r/20210512095458.30632-3-mgorman@techsingularity.net


Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 28f836b6

include/linux/mmzone.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/atomic.h>

#include <linux/atomic.h>

#include <linux/mm_types.h>

#include <linux/mm_types.h>

#include <linux/page-flags.h>

#include <linux/page-flags.h>

#include <linux/local_lock.h>

#include <asm/page.h>

#include <asm/page.h>





/* Free memory management - zoned buddy allocator.  */

/* Free memory management - zoned buddy allocator.  */
@@ -337,6 +338,7 @@ enum zone_watermarks { 
#define high_wmark_pages(z) (z->_watermark[WMARK_HIGH] + z->watermark_boost)

#define high_wmark_pages(z) (z->_watermark[WMARK_HIGH] + z->watermark_boost)

#define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost)

#define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost)





/* Fields and list protected by pagesets local_lock in page_alloc.c */

struct per_cpu_pages {

struct per_cpu_pages {

	int count;		/* number of pages in the list */

	int count;		/* number of pages in the list */

	int high;		/* high watermark, emptying needed */

	int high;		/* high watermark, emptying needed */

lib/Kconfig.debug

+3 −0
Original line number Original line Diff line number Diff line
@@ -313,6 +313,9 @@ config DEBUG_INFO_BTF 
config PAHOLE_HAS_SPLIT_BTF

config PAHOLE_HAS_SPLIT_BTF

	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")

	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "119")





config PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT

	def_bool $(success, test `$(PAHOLE) --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'` -ge "122")



config DEBUG_INFO_BTF_MODULES

config DEBUG_INFO_BTF_MODULES

	def_bool y

	def_bool y

	depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF

	depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF

mm/page_alloc.c

+46 −15
Original line number Original line Diff line number Diff line
@@ -122,6 +122,24 @@ typedef int __bitwise fpi_t; 
static DEFINE_MUTEX(pcp_batch_high_lock);

static DEFINE_MUTEX(pcp_batch_high_lock);

#define MIN_PERCPU_PAGELIST_FRACTION	(8)

#define MIN_PERCPU_PAGELIST_FRACTION	(8)





struct pagesets {

	local_lock_t lock;

#if defined(CONFIG_DEBUG_INFO_BTF) &&				\

	!defined(CONFIG_DEBUG_LOCK_ALLOC) &&			\

	!defined(CONFIG_PAHOLE_HAS_ZEROSIZE_PERCPU_SUPPORT)

	/*

	 * pahole 1.21 and earlier gets confused by zero-sized per-CPU

	 * variables and produces invalid BTF. Ensure that

	 * sizeof(struct pagesets) != 0 for older versions of pahole.

	 */

	char __pahole_hack;

	#warning "pahole too old to support zero-sized struct pagesets"

#endif

};

static DEFINE_PER_CPU(struct pagesets, pagesets) = {

	.lock = INIT_LOCAL_LOCK(lock),

};



#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID

#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID

DEFINE_PER_CPU(int, numa_node);

DEFINE_PER_CPU(int, numa_node);

EXPORT_PER_CPU_SYMBOL(numa_node);

EXPORT_PER_CPU_SYMBOL(numa_node);
@@ -1453,6 +1471,10 @@ static void free_pcppages_bulk(struct zone *zone, int count, 
		} while (--count && --batch_free && !list_empty(list));

		} while (--count && --batch_free && !list_empty(list));

	}

	}





	/*

	 * local_lock_irq held so equivalent to spin_lock_irqsave for

	 * both PREEMPT_RT and non-PREEMPT_RT configurations.

	 */

	spin_lock(&zone->lock);

	spin_lock(&zone->lock);

	isolated_pageblocks = has_isolate_pageblock(zone);

	isolated_pageblocks = has_isolate_pageblock(zone);
@@ -1573,6 +1595,11 @@ static void __free_pages_ok(struct page *page, unsigned int order, 
		return;

		return;





	migratetype = get_pfnblock_migratetype(page, pfn);

	migratetype = get_pfnblock_migratetype(page, pfn);



	/*

	 * TODO FIX: Disable IRQs before acquiring IRQ-safe zone->lock

	 * and protect vmstat updates.

	 */

	local_irq_save(flags);

	local_irq_save(flags);

	__count_vm_events(PGFREE, 1 << order);

	__count_vm_events(PGFREE, 1 << order);

	free_one_page(page_zone(page), page, pfn, order, migratetype,

	free_one_page(page_zone(page), page, pfn, order, migratetype,
@@ -2955,6 +2982,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, 
{

{

	int i, allocated = 0;

	int i, allocated = 0;





	/*

	 * local_lock_irq held so equivalent to spin_lock_irqsave for

	 * both PREEMPT_RT and non-PREEMPT_RT configurations.

	 */

	spin_lock(&zone->lock);

	spin_lock(&zone->lock);

	for (i = 0; i < count; ++i) {

	for (i = 0; i < count; ++i) {

		struct page *page = __rmqueue(zone, order, migratetype,

		struct page *page = __rmqueue(zone, order, migratetype,
@@ -3007,12 +3038,12 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp) 
	unsigned long flags;

	unsigned long flags;

	int to_drain, batch;

	int to_drain, batch;





	local_irq_save(flags);

	local_lock_irqsave(&pagesets.lock, flags);

	batch = READ_ONCE(pcp->batch);

	batch = READ_ONCE(pcp->batch);

	to_drain = min(pcp->count, batch);

	to_drain = min(pcp->count, batch);

	if (to_drain > 0)

	if (to_drain > 0)

		free_pcppages_bulk(zone, to_drain, pcp);

		free_pcppages_bulk(zone, to_drain, pcp);

	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);

}

}

#endif

#endif
@@ -3028,13 +3059,13 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone) 
	unsigned long flags;

	unsigned long flags;

	struct per_cpu_pages *pcp;

	struct per_cpu_pages *pcp;





	local_irq_save(flags);

	local_lock_irqsave(&pagesets.lock, flags);





	pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);

	pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu);

	if (pcp->count)

	if (pcp->count)

		free_pcppages_bulk(zone, pcp->count, pcp);

		free_pcppages_bulk(zone, pcp->count, pcp);





	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);

}

}





/*

/*
@@ -3297,9 +3328,9 @@ void free_unref_page(struct page *page) 
	if (!free_unref_page_prepare(page, pfn))

	if (!free_unref_page_prepare(page, pfn))

		return;

		return;





	local_irq_save(flags);

	local_lock_irqsave(&pagesets.lock, flags);

	free_unref_page_commit(page, pfn);

	free_unref_page_commit(page, pfn);

	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);

}

}





/*

/*
@@ -3319,7 +3350,7 @@ void free_unref_page_list(struct list_head *list) 
		set_page_private(page, pfn);

		set_page_private(page, pfn);

	}

	}





	local_irq_save(flags);

	local_lock_irqsave(&pagesets.lock, flags);

	list_for_each_entry_safe(page, next, list, lru) {

	list_for_each_entry_safe(page, next, list, lru) {

		unsigned long pfn = page_private(page);

		unsigned long pfn = page_private(page);
@@ -3332,12 +3363,12 @@ void free_unref_page_list(struct list_head *list) 
		 * a large list of pages to free.

		 * a large list of pages to free.

		 */

		 */

		if (++batch_count == SWAP_CLUSTER_MAX) {

		if (++batch_count == SWAP_CLUSTER_MAX) {

			local_irq_restore(flags);

			local_unlock_irqrestore(&pagesets.lock, flags);

			batch_count = 0;

			batch_count = 0;

			local_irq_save(flags);

			local_lock_irqsave(&pagesets.lock, flags);

		}

		}

	}

	}

	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);

}

}





/*

/*
@@ -3494,7 +3525,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, 
	struct page *page;

	struct page *page;

	unsigned long flags;

	unsigned long flags;





	local_irq_save(flags);

	local_lock_irqsave(&pagesets.lock, flags);

	pcp = this_cpu_ptr(zone->per_cpu_pageset);

	pcp = this_cpu_ptr(zone->per_cpu_pageset);

	list = &pcp->lists[migratetype];

	list = &pcp->lists[migratetype];

	page = __rmqueue_pcplist(zone,  migratetype, alloc_flags, pcp, list);

	page = __rmqueue_pcplist(zone,  migratetype, alloc_flags, pcp, list);
@@ -3502,7 +3533,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, 
		__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);

		__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);

		zone_statistics(preferred_zone, zone);

		zone_statistics(preferred_zone, zone);

	}

	}

	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);

	return page;

	return page;

}

}
@@ -5103,7 +5134,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, 
		goto failed;

		goto failed;





	/* Attempt the batch allocation */

	/* Attempt the batch allocation */

	local_irq_save(flags);

	local_lock_irqsave(&pagesets.lock, flags);

	pcp = this_cpu_ptr(zone->per_cpu_pageset);

	pcp = this_cpu_ptr(zone->per_cpu_pageset);

	pcp_list = &pcp->lists[ac.migratetype];

	pcp_list = &pcp->lists[ac.migratetype];
@@ -5141,12 +5172,12 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, 
		nr_populated++;

		nr_populated++;

	}

	}





	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);





	return nr_populated;

	return nr_populated;





failed_irq:

failed_irq:

	local_irq_restore(flags);

	local_unlock_irqrestore(&pagesets.lock, flags);





failed:

failed:

	page = __alloc_pages(gfp, 0, preferred_nid, nodemask);

	page = __alloc_pages(gfp, 0, preferred_nid, nodemask);