+ mm-vmallocc-optimize-code-in-decay_va_pool_node-a-little-bit.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/vmalloc.c: optimize code in decay_va_pool_node() a little bit
has been added to the -mm mm-new branch.  Its filename is
     mm-vmallocc-optimize-code-in-decay_va_pool_node-a-little-bit.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmallocc-optimize-code-in-decay_va_pool_node-a-little-bit.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Baoquan He <bhe@redhat.com>
Subject: mm/vmalloc.c: optimize code in decay_va_pool_node() a little bit
Date: Sat, 19 Apr 2025 06:36:51 +0800

When purge lazily freed vmap areas, VA stored in vn->pool[] will also be
taken away into free vmap tree partially or completely accordingly, that
is done in decay_va_pool_node().  When doing that, for each pool of node,
the whole list is detached from the pool for handling.  At this time, that
pool is empty.  It's not necessary to update the pool size each time when
one VA is removed and addded into free vmap tree.

Here change code to update the pool size when attaching the pool back.

Link: https://lkml.kernel.org/r/20250418223653.243436-4-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: Shivank Garg <shivankg@amd.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmalloc.c |   23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

--- a/mm/vmalloc.c~mm-vmallocc-optimize-code-in-decay_va_pool_node-a-little-bit
+++ a/mm/vmalloc.c
@@ -2149,7 +2149,7 @@ decay_va_pool_node(struct vmap_node *vn,
 	LIST_HEAD(decay_list);
 	struct rb_root decay_root = RB_ROOT;
 	struct vmap_area *va, *nva;
-	unsigned long n_decay;
+	unsigned long n_decay, pool_len;
 	int i;
 
 	for (i = 0; i < MAX_VA_SIZE_PAGES; i++) {
@@ -2163,22 +2163,20 @@ decay_va_pool_node(struct vmap_node *vn,
 		list_replace_init(&vn->pool[i].head, &tmp_list);
 		spin_unlock(&vn->pool_lock);
 
-		if (full_decay)
-			WRITE_ONCE(vn->pool[i].len, 0);
+		pool_len = n_decay = vn->pool[i].len;
+		WRITE_ONCE(vn->pool[i].len, 0);
 
 		/* Decay a pool by ~25% out of left objects. */
-		n_decay = vn->pool[i].len >> 2;
+		if (!full_decay)
+			n_decay >>= 2;
+		pool_len -= n_decay;
 
 		list_for_each_entry_safe(va, nva, &tmp_list, list) {
+			if (!n_decay--)
+				break;
+
 			list_del_init(&va->list);
 			merge_or_add_vmap_area(va, &decay_root, &decay_list);
-
-			if (!full_decay) {
-				WRITE_ONCE(vn->pool[i].len, vn->pool[i].len - 1);
-
-				if (!--n_decay)
-					break;
-			}
 		}
 
 		/*
@@ -2187,9 +2185,10 @@ decay_va_pool_node(struct vmap_node *vn,
 		 * can populate the pool therefore a simple list replace
 		 * operation takes place here.
 		 */
-		if (!full_decay && !list_empty(&tmp_list)) {
+		if (!list_empty(&tmp_list)) {
 			spin_lock(&vn->pool_lock);
 			list_replace_init(&tmp_list, &vn->pool[i].head);
+			WRITE_ONCE(vn->pool[i].len, pool_len);
 			spin_unlock(&vn->pool_lock);
 		}
 	}
_

Patches currently in -mm which might be from bhe@redhat.com are

mm-gup-remove-unneeded-checking-in-follow_page_pte.patch
mm-gup-remove-gup_fast_pgd_leaf-and-clean-up-the-relevant-codes.patch
mm-gup-clean-up-codes-in-fault_in_xxx-functions.patch
mm-gup-clean-up-codes-in-fault_in_xxx-functions-v5.patch
mm-vmallocc-change-purge_ndoes-as-local-static-variable.patch
mm-vmallocc-find-the-vmap-of-vmap_nodes-in-reverse-order.patch
mm-vmallocc-optimize-code-in-decay_va_pool_node-a-little-bit.patch
mm-vmalloc-optimize-function-vm_unmap_aliases.patch
mm-vmallocc-return-explicit-error-value-in-alloc_vmap_area.patch