Commit b0c82817 authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Peng Zhang
Browse files

mm: vmalloc: improve description of vmap node layer 

mainline inclusion
from mainline-v6.9-rc1
commit 15e02a39fb6b43f37100563c6a246252d5d1e6da
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9CHG1
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=15e02a39fb6b43f37100563c6a246252d5d1e6da

-------------------------------------------------

This patch adds extra explanation of recently added vmap node layer based
on community feedback.  No functional change.

Link: https://lkml.kernel.org/r/20240124180920.50725-1-urezki@gmail.com


Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 15e02a39fb6b43f37100563c6a246252d5d1e6da)
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: default avatarZhangPeng <zhangpeng362@huawei.com>
parent ecc3f0bf

mm/vmalloc.c

+46 −14
Original line number Diff line number Diff line
@@ -837,9 +837,10 @@ static struct rb_root free_vmap_area_root = RB_ROOT; 
static DEFINE_PER_CPU(struct vmap_area *, ne_fit_preload_node);



/*

 * An effective vmap-node logic. Users make use of nodes instead

 * of a global heap. It allows to balance an access and mitigate

 * contention.

 * This structure defines a single, solid model where a list and

 * rb-tree are part of one entity protected by the lock. Nodes are

 * sorted in ascending order, thus for O(1) access to left/right

 * neighbors a list is used as well as for sequential traversal.

 */

struct rb_list {

	struct rb_root root;
@@ -847,16 +848,23 @@ struct rb_list { 
	spinlock_t lock;

};



/*

 * A fast size storage contains VAs up to 1M size. A pool consists

 * of linked between each other ready to go VAs of certain sizes.

 * An index in the pool-array corresponds to number of pages + 1.

 */

#define MAX_VA_SIZE_PAGES 256



struct vmap_pool {

	struct list_head head;

	unsigned long len;

};



/*

 * A fast size storage contains VAs up to 1M size.

 * An effective vmap-node logic. Users make use of nodes instead

 * of a global heap. It allows to balance an access and mitigate

 * contention.

 */

#define MAX_VA_SIZE_PAGES 256



static struct vmap_node {

	/* Simple size segregated storage. */

	struct vmap_pool pool[MAX_VA_SIZE_PAGES];
@@ -875,6 +883,11 @@ static struct vmap_node { 
	unsigned long nr_purged;

} single;



/*

 * Initial setup consists of one single node, i.e. a balancing

 * is fully disabled. Later on, after vmap is initialized these

 * parameters are updated based on a system capacity.

 */

static struct vmap_node *vmap_nodes = &single;

static __read_mostly unsigned int nr_vmap_nodes = 1;

static __read_mostly unsigned int vmap_zone_size = 1;
@@ -2120,7 +2133,12 @@ decay_va_pool_node(struct vmap_node *vn, bool full_decay) 
			}

		}



		/* Attach the pool back if it has been partly decayed. */

		/*

		 * Attach the pool back if it has been partly decayed.

		 * Please note, it is supposed that nobody(other contexts)

		 * can populate the pool therefore a simple list replace

		 * operation takes place here.

		 */

		if (!full_decay && !list_empty(&tmp_list)) {

			spin_lock(&vn->pool_lock);

			list_replace_init(&tmp_list, &vn->pool[i].head);
@@ -2329,16 +2347,14 @@ struct vmap_area *find_vmap_area(unsigned long addr) 
	 * An addr_to_node_id(addr) converts an address to a node index

	 * where a VA is located. If VA spans several zones and passed

	 * addr is not the same as va->va_start, what is not common, we

	 * may need to scan an extra nodes. See an example:

	 * may need to scan extra nodes. See an example:

	 *

	 *      <--va-->

	 *      <----va---->

	 * -|-----|-----|-----|-----|-

	 *     1     2     0     1

	 *

	 * VA resides in node 1 whereas it spans 1 and 2. If passed

	 * addr is within a second node we should do extra work. We

	 * should mention that it is rare and is a corner case from

	 * the other hand it has to be covered.

	 * VA resides in node 1 whereas it spans 1, 2 an 0. If passed

	 * addr is within 2 or 0 nodes we should do extra work.

	 */

	i = j = addr_to_node_id(addr);

	do {
@@ -2361,6 +2377,9 @@ static struct vmap_area *find_unlink_vmap_area(unsigned long addr) 
	struct vmap_area *va;

	int i, j;



	/*

	 * Check the comment in the find_vmap_area() about the loop.

	 */

	i = j = addr_to_node_id(addr);

	do {

		vn = &vmap_nodes[i];
@@ -5160,7 +5179,20 @@ static void vmap_init_nodes(void) 
	int i, n;



#if BITS_PER_LONG == 64

	/* A high threshold of max nodes is fixed and bound to 128. */

	/*

	 * A high threshold of max nodes is fixed and bound to 128,

	 * thus a scale factor is 1 for systems where number of cores

	 * are less or equal to specified threshold.

	 *

	 * As for NUMA-aware notes. For bigger systems, for example

	 * NUMA with multi-sockets, where we can end-up with thousands

	 * of cores in total, a "sub-numa-clustering" should be added.

	 *

	 * In this case a NUMA domain is considered as a single entity

	 * with dedicated sub-nodes in it which describe one group or

	 * set of cores. Therefore a per-domain purging is supposed to

	 * be added as well as a per-domain balancing.

	 */

	n = clamp_t(unsigned int, num_possible_cpus(), 1, 128);



	if (n > 1) {