From: nikolay@redhat.com Date: Thu, 1 Aug 2013 14:54:51 +0000 (+0200) Subject: bonding: initial RCU conversion X-Git-Tag: v3.12-rc1~132^2~380^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=278b20837511776dc9d5f6ee1c7fabd5479838bb;p=pandora-kernel.git bonding: initial RCU conversion This patch does the initial bonding conversion to RCU. After it the following modes are protected by RCU alone: roundrobin, active-backup, broadcast and xor. Modes ALB/TLB and 3ad still acquire bond->lock for reading, and will be dealt with later. curr_active_slave needs to be dereferenced via rcu in the converted modes because the only thing protecting the slave after this patch is rcu_read_lock, so we need the proper barrier for weakly ordered archs and to make sure we don't have stale pointer. It's not tagged with __rcu yet because there's still work to be done to remove the curr_slave_lock, so sparse will complain when rcu_assign_pointer and rcu_dereference are used, but the alternative to use rcu_dereference_protected would've created much bigger code churn which is more difficult to test and review. That will be converted in time. 1. Active-backup mode 1.1 Perf recording while doing iperf -P 4 - old bonding: iperf spent 0.55% in bonding, system spent 0.29% CPU in bonding - new bonding: iperf spent 0.29% in bonding, system spent 0.15% CPU in bonding 1.2. Bandwidth measurements - old bonding: 16.1 gbps consistently - new bonding: 17.5 gbps consistently 2. Round-robin mode 2.1 Perf recording while doing iperf -P 4 - old bonding: iperf spent 0.51% in bonding, system spent 0.24% CPU in bonding - new bonding: iperf spent 0.16% in bonding, system spent 0.11% CPU in bonding 2.2 Bandwidth measurements - old bonding: 8 gbps (variable due to packet reorderings) - new bonding: 10 gbps (variable due to packet reorderings) Of course the latency has improved in all converted modes, and moreover while doing enslave/release (since it doesn't affect tx anymore). Also I've stress tested all modes doing enslave/release in a loop while transmitting traffic. Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- Reading git-diff-tree failed