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author | Ido Schimmel <idosch@nvidia.com> | 2020-10-16 20:29:14 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-29 12:07:07 +0300 |
commit | a81996aa6ee5887e939f48535601dc0ce814d095 (patch) | |
tree | edfbf3a047dd4e8dd537ac9b7b443e336c98a07b /net | |
parent | 8672e0e1be10f576e79b14abb3051574305bef0c (diff) | |
download | linux-a81996aa6ee5887e939f48535601dc0ce814d095.tar.xz |
nexthop: Fix performance regression in nexthop deletion
[ Upstream commit df6afe2f7c19349de2ee560dc62ea4d9ad3ff889 ]
While insertion of 16k nexthops all using the same netdev ('dummy10')
takes less than a second, deletion takes about 130 seconds:
# time -p ip -b nexthop.batch
real 0.29
user 0.01
sys 0.15
# time -p ip link set dev dummy10 down
real 131.03
user 0.06
sys 0.52
This is because of repeated calls to synchronize_rcu() whenever a
nexthop is removed from a nexthop group:
# /usr/share/bcc/tools/offcputime -p `pgrep -nx ip` -K
...
b'finish_task_switch'
b'schedule'
b'schedule_timeout'
b'wait_for_completion'
b'__wait_rcu_gp'
b'synchronize_rcu.part.0'
b'synchronize_rcu'
b'__remove_nexthop'
b'remove_nexthop'
b'nexthop_flush_dev'
b'nh_netdev_event'
b'raw_notifier_call_chain'
b'call_netdevice_notifiers_info'
b'__dev_notify_flags'
b'dev_change_flags'
b'do_setlink'
b'__rtnl_newlink'
b'rtnl_newlink'
b'rtnetlink_rcv_msg'
b'netlink_rcv_skb'
b'rtnetlink_rcv'
b'netlink_unicast'
b'netlink_sendmsg'
b'____sys_sendmsg'
b'___sys_sendmsg'
b'__sys_sendmsg'
b'__x64_sys_sendmsg'
b'do_syscall_64'
b'entry_SYSCALL_64_after_hwframe'
- ip (277)
126554955
Since nexthops are always deleted under RTNL, synchronize_net() can be
used instead. It will call synchronize_rcu_expedited() which only blocks
for several microseconds as opposed to multiple milliseconds like
synchronize_rcu().
With this patch deletion of 16k nexthops takes less than a second:
# time -p ip link set dev dummy10 down
real 0.12
user 0.00
sys 0.04
Tested with fib_nexthops.sh which includes torture tests that prompted
the initial change:
# ./fib_nexthops.sh
...
Tests passed: 134
Tests failed: 0
Fixes: 90f33bffa382 ("nexthops: don't modify published nexthop groups")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Link: https://lore.kernel.org/r/20201016172914.643282-1-idosch@idosch.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r-- | net/ipv4/nexthop.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index 134e92382275..355c4499fa1b 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -842,7 +842,7 @@ static void remove_nexthop_from_groups(struct net *net, struct nexthop *nh, remove_nh_grp_entry(net, nhge, nlinfo); /* make sure all see the newly published array before releasing rtnl */ - synchronize_rcu(); + synchronize_net(); } static void remove_nexthop_group(struct nexthop *nh, struct nl_info *nlinfo) |