Mp info changes #16961
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Mp info changes #16961
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ton31337
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Oct 1, 2024
Signed-off-by: Donald Sharp <[email protected]>
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The mpath data structure has data that is only relevant for the first mpath in the list. It is not being used anywhere else. Let's document that a bit more. Signed-off-by: Donald Sharp <[email protected]>
Test was confusing. Add some useful data and clean up some debugs Signed-off-by: Donald Sharp <[email protected]>
Currently bgp multipath has these properties:
a) mp_info may or may not be on a single path, based
upon path perturbations in the past.
b) mp_info->count started counting at 0( meaning 1 ). As that the
bestpath path_info was never included in the count
c) The first mp_info in the list held the multipath data associated
with the multipath. As such if you were at any other node that data
was not filled in.
d) As such the mp_info's that are not first on the list basically
were just pointers to the corresponding bgp_path_info that was in
the multipath.
e) On bestpath calculation, a linklist(struct linklist *) of bgp_path_info's was
created.
f) This linklist was passed in to a comparison function that took the
old mpinfo list and compared it item by item to the linklist and
doing magic to figure out how to create a new mp_info list.
g) the old mp_info and the link list had to be memory managed and
freed up.
h) BGP_PATH_MULTIPATH is only set on non bestpath nodes in the
multipath.
This is really complicated. Let's change the algorithm to this:
a) When running bestpath, mark a bgp_path_info node that could be in the ecmp path as
BGP_PATH_MULTIPATH_NEW.
b) When running multipath, just walk the list of bgp_path_info's and if
it has BGP_PATH_MULTIPATH_NEW on it, decide if it is in BGP_MULTIPATH.
If we run out of space to put in the ecmp, clear the flag on the rest.
c) Clean up the counting of sometimes adding 1 to the mpath count.
d) Only allocate a mpath_info node for the bestpath. Clean it up
when done with it.
e) remove the unneeded list management associated with the linklist and
the mp_list.
This greatly simplifies multipath computation for bgp and reduces memory
load for large scale deployments.
2 full feeds in work_queue_run prior:
0 56367.471 1123 50193 493695 50362 493791 0 0 0 TE work_queue_run
BGP multipath info : 1941844 48 110780992 1941844 110780992
2 full feeds in work_queue_run after change:
1 52924.931 1296 40837 465968 41025 487390 0 0 1 TE work_queue_run
BGP multipath info : 970860 32 38836880 970866 38837120
Aproximately 4 seconds of saved cpu time for convergence and ~75 mb
smaller run time.
Signed-off-by: Donald Sharp <[email protected]>
This function is no doing any work. Let's remove. Signed-off-by: Donald Sharp <[email protected]>
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ton31337
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Oct 2, 2024
|
yes exactly. The only mp_info allocated is for the bestpath bgp_path_info node. |
Merged
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lguohan
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Dec 19, 2024
Why I did it Added patches from FRR to support scale of BGP neighbors to 256/514. Below are the patches Patch FRR Pull request 0069-lib-nexthop-code-should-use-uint16_t-for-nexthop-cou.patch FRRouting/frr#16967 0070-Allow-16-bit-size-for-nexthops.patch FRRouting/frr#17023 0071-zebra-Only-notify-dplane-work-pthread-when-needed.patch FRRouting/frr#17062 0072-Fix-up-improper-handling-of-nexthops-for-nexthop-tra.patch FRRouting/frr#17076 0073-remove-in6addr-cmp.patch FRRouting/frr#17312 0074-bgp-best-port-reordering.patch FRRouting/frr#15572 0075-bgp-mp-info-changes.patch FRRouting/frr#16961 0076-Optimizations-and-problem-fixing-for-large-scale-ecmp-from-bgp.patch FRRouting/frr#17229
dgsudharsan
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Dec 23, 2024
…net#21199) Why I did it Added patches from FRR to support scale of BGP neighbors to 256/514. Below are the patches Patch FRR Pull request 0069-lib-nexthop-code-should-use-uint16_t-for-nexthop-cou.patch FRRouting/frr#16967 0070-Allow-16-bit-size-for-nexthops.patch FRRouting/frr#17023 0071-zebra-Only-notify-dplane-work-pthread-when-needed.patch FRRouting/frr#17062 0072-Fix-up-improper-handling-of-nexthops-for-nexthop-tra.patch FRRouting/frr#17076 0073-remove-in6addr-cmp.patch FRRouting/frr#17312 0074-bgp-best-port-reordering.patch FRRouting/frr#15572 0075-bgp-mp-info-changes.patch FRRouting/frr#16961 0076-Optimizations-and-problem-fixing-for-large-scale-ecmp-from-bgp.patch FRRouting/frr#17229
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See last commit for full data. Effectively though, mp_info is expensive this reduces the cost by a decent amount.