git: a6b05a35ce3c - stable/14 - vfs: vntblinit(): Raise default 'kern.maxvnodes' higher than 'kern.maxfiles'

The branch stable/14 has been updated by olce:

URL: https://cgit.FreeBSD.org/src/commit/?id=a6b05a35ce3c516cadfca49c310dffaabbe40440

commit a6b05a35ce3c516cadfca49c310dffaabbe40440
Author:     Olivier Certner <olce@FreeBSD.org>
AuthorDate: 2025-05-12 12:19:56 +0000
Commit:     Olivier Certner <olce@FreeBSD.org>
CommitDate: 2025-05-20 09:05:33 +0000

    vfs: vntblinit(): Raise default 'kern.maxvnodes' higher than 'kern.maxfiles'
    
    Having 'kern.maxvnodes' higher than 'kern.maxfiles' mitigates a scenario
    where some processes can eat up all vnodes in the system, causing
    a deadlock, as long as the kernel itself does not create too many vnodes
    without creating some file descriptor in some process' FD table.  A very
    small percentage (~0.6%) of excess vnodes at infinity, coupled with
    a large difference near the origin, should cover basic cases more than
    enough.  Note however that this measure can be defeated, e.g., by using
    nullfs mounts with non-trivial file hierarchies.
    
    MFC after:      5 days
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D50314
    
    (cherry picked from commit e9baf472a6d228a16be19a11150d41cff29affe8)
---
 sys/kern/vfs_subr.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 62ae987a3084..7ff6ac5f5b44 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -727,13 +727,12 @@ vntblinit(void *dummy __unused)
 	 * KVA).
 	 *
 	 * Currently, on 64-bit platforms, 'desiredvnodes' is set to
-	 * 'virtvnodes' up to a physical memory cutoff of ~1674MB, after which
+	 * 'virtvnodes' up to a physical memory cutoff of ~1722MB, after which
 	 * 'physvnodes' applies instead.  With the current automatic tuning for
-	 * 'maxfiles' (32 files/MB), 'desiredvnodes' becomes smaller than it at
-	 * ~5136MB.
+	 * 'maxfiles' (32 files/MB), 'desiredvnodes' is always greater than it.
 	 */
-	physvnodes = maxproc + pgtok(vm_cnt.v_page_count) / 64 +
-	    3 * min(98304 * 16, pgtok(vm_cnt.v_page_count)) / 64;
+	physvnodes = maxproc + pgtok(vm_cnt.v_page_count) / 32 +
+	    min(98304 * 16, pgtok(vm_cnt.v_page_count)) / 32;
 	virtvnodes = vm_kmem_size / (10 * (sizeof(struct vm_object) +
 	    sizeof(struct vnode) + NC_SZ * ncsizefactor + NFS_NCLNODE_SZ));
 	desiredvnodes = min(physvnodes, virtvnodes);