git: fd56d2472586 - main - tarfs.5: Provide some guidance on zstd frame sizes

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=fd56d24725860a3c1f12180cf8503d38d8d0c70d

commit fd56d24725860a3c1f12180cf8503d38d8d0c70d
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2024-04-05 15:28:55 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2024-04-05 15:43:58 +0000

    tarfs.5: Provide some guidance on zstd frame sizes
    
    Reviewed by:    des, emaste
    MFC after:      2 weeks
    Sponsored by:   Klara, Inc.
    Differential Revision:  https://reviews.freebsd.org/D44636
---
 share/man/man5/tarfs.5 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/share/man/man5/tarfs.5 b/share/man/man5/tarfs.5
index 5378491b9c9f..56c56ac43287 100644
--- a/share/man/man5/tarfs.5
+++ b/share/man/man5/tarfs.5
@@ -74,6 +74,15 @@ to create the tar file, this can be achieved using the
 and
 .Cm ztsd:frame-per-file
 options.
+Sensible frame sizes are powers of 2 between the system's base page size
+(see
+.Xr arch 7 )
+and the value of the
+.Sy kern.maxphys
+sysctl.
+Smaller frames will generally yield a worse compression ratio and require extra
+kernel memory to maintain an index, and larger frames will on average require
+more CPU time to access data when performing random I/O.
 .Sh DIAGNOSTICS
 If enabled by the
 .Dv TARFS_DEBUG