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: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Baoquan 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: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index b5882790da00880e0b9abbe8af457f6d965d09f0..72822aeff55c22c7de63abdcc31fec4e14498671 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -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());
+       mutex_lock(&vmap_purge_lock);
+       __purge_vmap_area_lazy(ULONG_MAX, 0);
+       mutex_unlock(&vmap_purge_lock);
 }
 
 /*
@@ -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) {
-               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);
+       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(&vn->lazy.lock);
        }
-       spin_unlock(&purge_vmap_area_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);
        }
 }