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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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32b293a53d
During some debugging I needed to look into how /proc/net/ipv6_route
operated and in my digging I found its calling fib6_clean_all() which uses
"write_lock_bh(&table->tb6_lock)" before doing the walk of the table. I
found this on 2.6.32, but reading the code I believe the same basic idea
exists currently. Looking at the rtnetlink code they are only calling
"read_lock_bh(&table->tb6_lock);" via fib6_dump_table(). While I realize
reading from proc isn't the recommended way of fetching the ipv6 route
table; taking a write lock seems unnecessary and would probably cause
network performance issues.
To verify this I loaded up the ipv6 route table and then ran iperf in 3
cases:
* doing nothing
* reading ipv6 route table via proc
(while :; do cat /proc/net/ipv6_route > /dev/null; done)
* reading ipv6 route table via rtnetlink
(while :; do ip -6 route show table all > /dev/null; done)
* Load the ipv6 route table up with:
* for ((i = 0;i < 4000;i++)); do ip route add unreachable 2000::$i; done
* iperf commands:
* client: iperf -i 1 -V -c <ipv6 addr>
* server: iperf -V -s
* iperf results - 3 runs each (in Mbits/sec)
* nothing: client: 927,927,927 server: 927,927,927
* proc: client: 179,97,96,113 server: 142,112,133
* iproute: client: 928,927,928 server: 927,927,927
lock_stat shows taking the write lock is causing the slowdown. Using this
info I decided to write a version of fib6_clean_all() which replaces
write_lock_bh(&table->tb6_lock) with read_lock_bh(&table->tb6_lock). With
this new function I see the same results as with my rtnetlink iperf test.
Signed-off-by: Josh Hunt <joshhunt00@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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|---|---|---|
| .. | ||
| netfilter | ||
| addrconf_core.c | ||
| addrconf.c | ||
| addrlabel.c | ||
| af_inet6.c | ||
| ah6.c | ||
| anycast.c | ||
| datagram.c | ||
| esp6.c | ||
| exthdrs_core.c | ||
| exthdrs.c | ||
| fib6_rules.c | ||
| icmp.c | ||
| inet6_connection_sock.c | ||
| inet6_hashtables.c | ||
| ip6_fib.c | ||
| ip6_flowlabel.c | ||
| ip6_input.c | ||
| ip6_output.c | ||
| ip6_tunnel.c | ||
| ip6mr.c | ||
| ipcomp6.c | ||
| ipv6_sockglue.c | ||
| Kconfig | ||
| Makefile | ||
| mcast.c | ||
| mip6.c | ||
| ndisc.c | ||
| netfilter.c | ||
| proc.c | ||
| protocol.c | ||
| raw.c | ||
| reassembly.c | ||
| route.c | ||
| sit.c | ||
| syncookies.c | ||
| sysctl_net_ipv6.c | ||
| tcp_ipv6.c | ||
| tunnel6.c | ||
| udp_impl.h | ||
| udp.c | ||
| udplite.c | ||
| xfrm6_input.c | ||
| xfrm6_mode_beet.c | ||
| xfrm6_mode_ro.c | ||
| xfrm6_mode_transport.c | ||
| xfrm6_mode_tunnel.c | ||
| xfrm6_output.c | ||
| xfrm6_policy.c | ||
| xfrm6_state.c | ||
| xfrm6_tunnel.c | ||