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David Ahern says:
====================
net: mpls: Allow users to configure more labels per route
Increase the maximum number of new labels for MPLS routes from 2 to 30.
To keep memory consumption in check, the labels array is moved to the end
of mpls_nh and mpls_iptunnel_encap structs as a 0-sized array. Allocations
use the maximum number of labels across all nexthops in a route for LSR
and the number of labels configured for LWT.
The mpls_route layout is changed to:
+----------------------+
| mpls_route |
+----------------------+
| mpls_nh 0 |
+----------------------+
| alignment padding | 4 bytes for odd number of labels; 0 for even
+----------------------+
| via[rt_max_alen] 0 |
+----------------------+
| alignment padding | via's aligned on sizeof(unsigned long)
+----------------------+
| ... |
Meaning the via follows its mpls_nh providing better locality as the
number of labels increases. UDP_RR tests with namespaces shows no impact
to a modest performance increase with this layout for 1 or 2 labels and
1 or 2 nexthops.
mpls_route allocation size is limited to 4096 bytes allowing on the
order of 30 nexthops with 30 labels (or more nexthops with fewer
labels). LWT encap shares same maximum number of labels as mpls routing.
v3
- initialize n_labels to 0 in case RTA_NEWDST is not defined; detected
by the kbuild test robot
v2
- updates per Eric's comments
+ added patch to ensure all reads of rt_nhn_alive and nh_flags in
the packet path use READ_ONCE and all writes via event handlers
use WRITE_ONCE
+ limit mpls_route size to 4096 (PAGE_SIZE for most arch)
+ mostly killed use of MAX_NEW_LABELS; it exists only for common
limit between lwt and routing paths
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.