From: "Uladzislau Rezki (Sony)" urezki@gmail.com
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/?i...
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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: Uladzislau Rezki (Sony) urezki@gmail.com Reviewed-by: Lorenzo 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: Andrew Morton akpm@linux-foundation.org (cherry picked from commit 15e02a39fb6b43f37100563c6a246252d5d1e6da) Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com Signed-off-by: ZhangPeng zhangpeng362@huawei.com --- mm/vmalloc.c | 60 ++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 46 insertions(+), 14 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index a1b67d5b9a5b..69b07e36b4f0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -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) {