Eric Dumazet wrote:
Chris Friesen a écrit :
Based on profiling and instrumentation it seems like the cost of
sctp_endpoint_lookup_assoc() more than triples, which means that the
amount of time that bottom halves are disabled in that function also
triples.
Any idea of the size of sctp hash size you have ?
(your dmesg probably includes a message starting with SCTP: Hash tables
configured...
How many concurrent sctp sockets are handled ?
Our lab is currently rebooting, but I'll try and get this once it's back up.
Maybe sctp_assoc_hashfn() is too weak for your use, and some chains are
*really* long.
Based on the profiling information we're spending time in
sctp_endpoint_lookup_assoc() which doesn't actually use hashes, so I
can't see how the hash would be related. I'm pretty new to SCTP though,
so I may be missing something.
Here's the top results from readprofile, unfortunately these are
aggregated across both cpus so they don't really show what's going on.
The key thing is that sctp_endpoint_lookup_assoc() is the most expensive
kernel routine on this entire system.
3147 .power4_idle 22.4786
1712 .native_idle 20.3810
1234 .sctp_endpoint_lookup_assoc 2.1725
1212 ._spin_unlock_irqrestore 6.4468
778 .do_futex 0.3791
447 ._spin_unlock_irq 4.2981
313 .fget 1.7784
277 .fput 3.8472
275 .kfree 0.7473
234 .__kmalloc 0.5571
131 SystemCall_common 0.3411
130 .sctp_assoc_is_match 0.6373
123 .lock_sock 0.4155
119 .find_vma 0.6919
116 .kmem_cache_alloc 0.3580
111 .kmem_cache_free 0.3343
106 .skb_release_data 0.4907
102 .__copy_tofrom_user 0.0724
100 .exit_elf_binfmt 1.9231
100 .do_select 0.0820
Chris
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