rrs - Lets make the LRO code look for true dup-acks and window update acks
fly on through and combine.
rrs - Make the LRO engine a bit more aware of ack-only seq space. Lets not
have it incorrectly wipe out newer acks for older acks when we have
out-of-order acks (common in wifi environments).
jeggleston - LRO eating window updates
Based on all of the above I think we are RFC compliant doing it this way:
https://tools.ietf.org/html/rfc1122
section 4.2.2.16
"Note that TCP has a heuristic to select the latest window update despite
possible datagram reordering; as a result, it may ignore a window update with
a smaller window than previously offered if neither the sequence number nor the
acknowledgment number is increased."
Submitted by: Kevin Bowling <kevin.bowling@kev009.com>
Reviewed by: rstone gallatin
Sponsored by: NetFlix and Limelight Networks
Differential Revision: https://reviews.freebsd.org/D14540
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
No functional change intended.
wait for the next enqueue from the driver.
Reviewed by: gnn@, hselasky@, gallatin@
MFC after: 1 week
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D10432
tso_segsz pkthdr field during RX processing, and use the information in TCP for
more correct accounting and as a congestion control input. This is only a start,
and an audit of other uses for the data is left as future work.
Reviewed by: gallatin, rrs
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D7564
This keeps the segments/ACK/FIN delivery order.
Before this patch, it was observed: if A sent FIN immediately after
an ACK, B would deliver FIN first to the TCP stack, then the ACK.
This out-of-order delivery causes one unnecessary ACK sent from B.
Reviewed by: gallatin, hps
Obtained from: rrs, gallatin
Sponsored by: Netflix (rrs, gallatin), Microsoft (sephe)
Differential Revision: https://reviews.freebsd.org/D7415
Replacing the bubble sort with insertion sort gives an 80% reduction
in runtime on average, with randomized keys, for small partitions.
If the keys are pre-sorted, insertion sort runs in linear time, and
even if the keys are reversed, insertion sort is faster than bubble
sort, although not by much.
Update comment describing "tcp_lro_sort()" while at it.
Differential Revision: https://reviews.freebsd.org/D6619
Sponsored by: Mellanox Technologies
Tested by: Netflix
Suggested by: Pieter de Goeje <pieter@degoeje.nl>
Reviewed by: ed, gallatin, gnn, transport
"qsort()".
The kernel's "qsort()" routine can in worst case spend O(N*N) amount of
comparisons before the input array is sorted. It can also recurse a
significant amount of times using up the kernel's interrupt thread
stack.
The custom sorting routine takes advantage of that the sorting key is
only 64 bits. Based on set and cleared bits in the sorting key it
partitions the array until it is sorted. This process has a recursion
limit of 64 times, due to the number of set and cleared bits which can
occur. Compiled with -O2 the sorting routine was measured to use
64-bytes of stack. Multiplying this by 64 gives a maximum stack
consumption of 4096 bytes for AMD64. The same applies to the execution
time, that the array to be sorted will not be traversed more than 64
times.
When serving roughly 80Gb/s with 80K TCP connections, the old method
consisting of "qsort()" and "tcp_lro_mbuf_compare_header()" used 1.4%
CPU, while the new "tcp_lro_sort()" used 1.1% for LRO related sorting
as measured by Intel Vtune. The testing was done using a sysctl to
toggle between "qsort()" and "tcp_lro_sort()".
Differential Revision: https://reviews.freebsd.org/D6472
Sponsored by: Mellanox Technologies
Tested by: Netflix
Reviewed by: gallatin, rrs, sephe, transport
Ease more work concerning active list, e.g. hash table etc.
Reviewed by: gallatin, rrs (earlier version)
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D6137
This is kinda critical to the performance when the CPU is slow and
network bandwidth is high, e.g. in the hypervisor.
Reviewed by: rrs, gallatin, Dexuan Cui <decui microsoft com>
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D5765
And factor out tcp_lro_rx_done, which deduplicates the same logic with
netinet/tcp_lro.c
Reviewed by: gallatin (1st version), hps, zbb, np, Dexuan Cui <decui microsoft com>
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D5725
So that callers could react accordingly.
Reviewed by: gallatin (no objection)
MFC after: 1 week
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D5695
ACK aggregation limit is append count based, while the TCP data segment
aggregation limit is length based. Unless the network driver sets these
two limits, it's an NO-OP.
Reviewed by: adrian, gallatin (previous version), hselasky (previous version)
Approved by: adrian (mentor)
MFC after: 1 week
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D5185
the sign bit doesn't cause an overflow. The overflow manifests itself
as a sorting index wrap around in the middle of the sorted array,
which is not a problem for the LRO code, but might be a problem for
the logic inside qsort().
Reviewed by: gnn @
Sponsored by: Mellanox Technologies
Differential Revision: https://reviews.freebsd.org/D5239
- Add optimizing LRO wrapper which pre-sorts all incoming packets
according to the hash type and flowid. This prevents exhaustion of
the LRO entries due to too many connections at the same time.
Testing using a larger number of higher bandwidth TCP connections
showed that the incoming ACK packet aggregation rate increased from
~1.3:1 to almost 3:1. Another test showed that for a number of TCP
connections greater than 16 per hardware receive ring, where 8 TCP
connections was the LRO active entry limit, there was a significant
improvement in throughput due to being able to fully aggregate more
than 8 TCP stream. For very few very high bandwidth TCP streams, the
optimizing LRO wrapper will add CPU usage instead of reducing CPU
usage. This is expected. Network drivers which want to use the
optimizing LRO wrapper needs to call "tcp_lro_queue_mbuf()" instead
of "tcp_lro_rx()" and "tcp_lro_flush_all()" instead of
"tcp_lro_flush()". Further the LRO control structure must be
initialized using "tcp_lro_init_args()" passing a non-zero number
into the "lro_mbufs" argument.
- Make LRO statistics 64-bit. Previously 32-bit integers were used for
statistics which can be prone to wrap-around. Fix this while at it
and update all SYSCTL's which expose LRO statistics.
- Ensure all data is freed when destroying a LRO control structures,
especially leftover LRO entries.
- Reduce number of memory allocations needed when setting up a LRO
control structure by precomputing the total amount of memory needed.
- Add own memory allocation counter for LRO.
- Bump the FreeBSD version to force recompilation of all KLDs due to
change of the LRO control structure size.
Sponsored by: Mellanox Technologies
Reviewed by: gallatin, sbruno, rrs, gnn, transport
Tested by: Netflix
Differential Revision: https://reviews.freebsd.org/D4914
Add a last-modified timestamp to each LRO entry and provide an interface
to flush all inactive entries. Drivers decide when to flush and what
the inactivity threshold should be.
Network drivers that process an rx queue to completion can enter a
livelock type situation when the rate at which packets are received
reaches equilibrium with the rate at which the rx thread is processing
them. When this happens the final LRO flush (normally when the rx
routine is done) does not occur. Pure ACKs and segments with total
payload < 64K can get stuck in an LRO entry. Symptoms are that TCP
tx-mostly connections' performance falls off a cliff during heavy,
unrelated rx on the interface.
Flushing only inactive LRO entries works better than any of these
alternates that I tried:
- don't LRO pure ACKs
- flush _all_ LRO entries periodically (every 'x' microseconds or every
'y' descriptors)
- stop rx processing in the driver periodically and schedule remaining
work for later.
Reviewed by: andre
Specifcially, in_cksum_hdr() returns 0 (not 0xffff) when the IPv4
checksum is correct. Without this fix, the tcp_lro code will reject
good IPv4 traffic from drivers that do not implement IPv4 header
harder csum offload.
Sponsored by: Myricom Inc.
MFC after: 7 days
queue the packet for LRO and tell the driver to directly pass it on.
This avoids re-assembly and later re-fragmentation problems when
forwarding.
It's not the best solution but the simplest and most effective for
the moment.
Should have been done: ages ago
Discussed with and by: many
MFC after: 3 days
Significantly update tcp_lro for mostly two things:
1) introduce basic support for IPv6 without extension headers.
2) try hard to also get the incremental checksum updates right,
especially also in the IPv4 case for the IP and TCP header.
Move variables around for better locality, factor things out into
functions, allow checksum updates to be compiled out, ...
Leave a few comments on further things to look at in the future,
though that is not the full list.
Update drivers with appropriate #includes as needed for IPv6 data
type in LRO.
Sponsored by: The FreeBSD Foundation
Sponsored by: iXsystems
Reviewed by: gnn (as part of the whole)
MFC After: 3 days
when len is inserted back into the synthetic IP packet and cause a
multiple of 2^16 bytes of TCP "packet loss".
This improves Linux->FreeBSD netperf bandwidth by a factor of 300 in
testing on Amazon EC2.
Reviewed by: jfv
MFC after: 2 weeks
