Commit 282631cb authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Andrew Morton
Browse files

mm: vmalloc: remove global purge_vmap_area_root rb-tree 

Similar to busy VA, lazily-freed area is stored to a node it belongs to. 
Such approach does not require any global locking primitive, instead an
access becomes scalable what mitigates a contention.

This patch removes a global purge-lock, global purge-tree and global purge
list.

Link: https://lkml.kernel.org/r/20240102184633.748113-7-urezki@gmail.com


Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: default avatarBaoquan He <bhe@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Kazuhito Hagio <k-hagio-ab@nec.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 55c49fee

mm/vmalloc.c

+82 −53
Original line number Diff line number Diff line
@@ -731,10 +731,6 @@ EXPORT_SYMBOL(vmalloc_to_pfn); 
static DEFINE_SPINLOCK(free_vmap_area_lock);

static bool vmap_initialized __read_mostly;



static struct rb_root purge_vmap_area_root = RB_ROOT;

static LIST_HEAD(purge_vmap_area_list);

static DEFINE_SPINLOCK(purge_vmap_area_lock);



/*

 * This kmem_cache is used for vmap_area objects. Instead of

 * allocating from slab we reuse an object from this cache to
@@ -782,6 +778,12 @@ struct rb_list { 
static struct vmap_node {

	/* Bookkeeping data of this node. */

	struct rb_list busy;

	struct rb_list lazy;



	/*

	 * Ready-to-free areas.

	 */

	struct list_head purge_list;

} single;



static struct vmap_node *vmap_nodes = &single;
@@ -1766,40 +1768,22 @@ static DEFINE_MUTEX(vmap_purge_lock); 


/* for per-CPU blocks */

static void purge_fragmented_blocks_allcpus(void);

static cpumask_t purge_nodes;



/*

 * Purges all lazily-freed vmap areas.

 */

static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)

static unsigned long

purge_vmap_node(struct vmap_node *vn)

{

	unsigned long resched_threshold;

	unsigned int num_purged_areas = 0;

	struct list_head local_purge_list;

	unsigned long num_purged_areas = 0;

	struct vmap_area *va, *n_va;



	lockdep_assert_held(&vmap_purge_lock);



	spin_lock(&purge_vmap_area_lock);

	purge_vmap_area_root = RB_ROOT;

	list_replace_init(&purge_vmap_area_list, &local_purge_list);

	spin_unlock(&purge_vmap_area_lock);



	if (unlikely(list_empty(&local_purge_list)))

		goto out;



	start = min(start,

		list_first_entry(&local_purge_list,

			struct vmap_area, list)->va_start);



	end = max(end,

		list_last_entry(&local_purge_list,

			struct vmap_area, list)->va_end);



	flush_tlb_kernel_range(start, end);

	resched_threshold = lazy_max_pages() << 1;

	if (list_empty(&vn->purge_list))

		return 0;



	spin_lock(&free_vmap_area_lock);

	list_for_each_entry_safe(va, n_va, &local_purge_list, list) {

	list_for_each_entry_safe(va, n_va, &vn->purge_list, list) {

		unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT;

		unsigned long orig_start = va->va_start;

		unsigned long orig_end = va->va_end;
@@ -1821,13 +1805,55 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) 


		atomic_long_sub(nr, &vmap_lazy_nr);

		num_purged_areas++;



		if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)

			cond_resched_lock(&free_vmap_area_lock);

	}

	spin_unlock(&free_vmap_area_lock);



out:

	return num_purged_areas;

}



/*

 * Purges all lazily-freed vmap areas.

 */

static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)

{

	unsigned long num_purged_areas = 0;

	struct vmap_node *vn;

	int i;



	lockdep_assert_held(&vmap_purge_lock);

	purge_nodes = CPU_MASK_NONE;



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

		vn = &vmap_nodes[i];



		INIT_LIST_HEAD(&vn->purge_list);



		if (RB_EMPTY_ROOT(&vn->lazy.root))

			continue;



		spin_lock(&vn->lazy.lock);

		WRITE_ONCE(vn->lazy.root.rb_node, NULL);

		list_replace_init(&vn->lazy.head, &vn->purge_list);

		spin_unlock(&vn->lazy.lock);



		start = min(start, list_first_entry(&vn->purge_list,

			struct vmap_area, list)->va_start);



		end = max(end, list_last_entry(&vn->purge_list,

			struct vmap_area, list)->va_end);



		cpumask_set_cpu(i, &purge_nodes);

	}



	if (cpumask_weight(&purge_nodes) > 0) {

		flush_tlb_kernel_range(start, end);



		for_each_cpu(i, &purge_nodes) {

			vn = &nodes[i];

			num_purged_areas += purge_vmap_node(vn);

		}

	}



	trace_purge_vmap_area_lazy(start, end, num_purged_areas);

	return num_purged_areas > 0;

}
@@ -1846,16 +1872,9 @@ static void reclaim_and_purge_vmap_areas(void) 


static void drain_vmap_area_work(struct work_struct *work)

{

	unsigned long nr_lazy;



	do {

	mutex_lock(&vmap_purge_lock);

	__purge_vmap_area_lazy(ULONG_MAX, 0);

	mutex_unlock(&vmap_purge_lock);



		/* Recheck if further work is required. */

		nr_lazy = atomic_long_read(&vmap_lazy_nr);

	} while (nr_lazy > lazy_max_pages());

}



/*
@@ -1865,6 +1884,7 @@ static void drain_vmap_area_work(struct work_struct *work) 
 */

static void free_vmap_area_noflush(struct vmap_area *va)

{

	struct vmap_node *vn = addr_to_node(va->va_start);

	unsigned long nr_lazy_max = lazy_max_pages();

	unsigned long va_start = va->va_start;

	unsigned long nr_lazy;
@@ -1878,10 +1898,9 @@ static void free_vmap_area_noflush(struct vmap_area *va) 
	/*

	 * Merge or place it to the purge tree/list.

	 */

	spin_lock(&purge_vmap_area_lock);

	merge_or_add_vmap_area(va,

		&purge_vmap_area_root, &purge_vmap_area_list);

	spin_unlock(&purge_vmap_area_lock);

	spin_lock(&vn->lazy.lock);

	merge_or_add_vmap_area(va, &vn->lazy.root, &vn->lazy.head);

	spin_unlock(&vn->lazy.lock);



	trace_free_vmap_area_noflush(va_start, nr_lazy, nr_lazy_max);
@@ -4411,15 +4430,21 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v) 


static void show_purge_info(struct seq_file *m)

{

	struct vmap_node *vn;

	struct vmap_area *va;

	int i;



	spin_lock(&purge_vmap_area_lock);

	list_for_each_entry(va, &purge_vmap_area_list, list) {

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

		vn = &vmap_nodes[i];



		spin_lock(&vn->lazy.lock);

		list_for_each_entry(va, &vn->lazy.head, list) {

			seq_printf(m, "0x%pK-0x%pK %7ld unpurged vm_area\n",

				(void *)va->va_start, (void *)va->va_end,

				va->va_end - va->va_start);

		}

	spin_unlock(&purge_vmap_area_lock);

		spin_unlock(&vn->lazy.lock);

	}

}



static int s_show(struct seq_file *m, void *p)
@@ -4558,6 +4583,10 @@ static void vmap_init_nodes(void) 
		vn->busy.root = RB_ROOT;

		INIT_LIST_HEAD(&vn->busy.head);

		spin_lock_init(&vn->busy.lock);



		vn->lazy.root = RB_ROOT;

		INIT_LIST_HEAD(&vn->lazy.head);

		spin_lock_init(&vn->lazy.lock);

	}

}