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Commit 80c4bd7a authored by Chris Wilson's avatar Chris Wilson Committed by Linus Torvalds
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mm/vmalloc: keep a separate lazy-free list 



When mixing lots of vmallocs and set_memory_*() (which calls
vm_unmap_aliases()) I encountered situations where the performance
degraded severely due to the walking of the entire vmap_area list each
invocation.

One simple improvement is to add the lazily freed vmap_area to a
separate lockless free list, such that we then avoid having to walk the
full list on each purge.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarRoman Pen <r.peniaev@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Roman Pen <r.peniaev@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f705ac4b

include/linux/vmalloc.h

+2 −1
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
#include <linux/spinlock.h>

#include <linux/init.h>

#include <linux/list.h>

#include <linux/llist.h>

#include <asm/page.h>		/* pgprot_t */

#include <linux/rbtree.h>
@@ -44,7 +45,7 @@ struct vmap_area { 
	unsigned long flags;

	struct rb_node rb_node;         /* address sorted rbtree */

	struct list_head list;          /* address sorted list */

	struct list_head purge_list;    /* "lazy purge" list */

	struct llist_node purge_list;    /* "lazy purge" list */

	struct vm_struct *vm;

	struct rcu_head rcu_head;

};

mm/vmalloc.c

+19 −20
Original line number Diff line number Diff line
@@ -274,13 +274,12 @@ EXPORT_SYMBOL(vmalloc_to_pfn); 


/*** Global kva allocator ***/



#define VM_LAZY_FREE	0x01

#define VM_LAZY_FREEING	0x02

#define VM_VM_AREA	0x04



static DEFINE_SPINLOCK(vmap_area_lock);

/* Export for kexec only */

LIST_HEAD(vmap_area_list);

static LLIST_HEAD(vmap_purge_list);

static struct rb_root vmap_area_root = RB_ROOT;



/* The vmap cache globals are protected by vmap_area_lock */
@@ -601,7 +600,7 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, 
					int sync, int force_flush)

{

	static DEFINE_SPINLOCK(purge_lock);

	LIST_HEAD(valist);

	struct llist_node *valist;

	struct vmap_area *va;

	struct vmap_area *n_va;

	int nr = 0;
@@ -620,20 +619,14 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, 
	if (sync)

		purge_fragmented_blocks_allcpus();



	rcu_read_lock();

	list_for_each_entry_rcu(va, &vmap_area_list, list) {

		if (va->flags & VM_LAZY_FREE) {

	valist = llist_del_all(&vmap_purge_list);

	llist_for_each_entry(va, valist, purge_list) {

		if (va->va_start < *start)

			*start = va->va_start;

		if (va->va_end > *end)

			*end = va->va_end;

		nr += (va->va_end - va->va_start) >> PAGE_SHIFT;

			list_add_tail(&va->purge_list, &valist);

			va->flags |= VM_LAZY_FREEING;

			va->flags &= ~VM_LAZY_FREE;

		}

	}

	rcu_read_unlock();



	if (nr)

		atomic_sub(nr, &vmap_lazy_nr);
@@ -643,7 +636,7 @@ static void __purge_vmap_area_lazy(unsigned long *start, unsigned long *end, 


	if (nr) {

		spin_lock(&vmap_area_lock);

		list_for_each_entry_safe(va, n_va, &valist, purge_list)

		llist_for_each_entry_safe(va, n_va, valist, purge_list)

			__free_vmap_area(va);

		spin_unlock(&vmap_area_lock);

	}
@@ -678,9 +671,15 @@ static void purge_vmap_area_lazy(void) 
 */

static void free_vmap_area_noflush(struct vmap_area *va)

{

	va->flags |= VM_LAZY_FREE;

	atomic_add((va->va_end - va->va_start) >> PAGE_SHIFT, &vmap_lazy_nr);

	if (unlikely(atomic_read(&vmap_lazy_nr) > lazy_max_pages()))

	int nr_lazy;



	nr_lazy = atomic_add_return((va->va_end - va->va_start) >> PAGE_SHIFT,

				    &vmap_lazy_nr);



	/* After this point, we may free va at any time */

	llist_add(&va->purge_list, &vmap_purge_list);



	if (unlikely(nr_lazy > lazy_max_pages()))

		try_purge_vmap_area_lazy();

}