On Tue, May 20, 2003 at 05:36:07PM -0700, David S. Miller wrote:
> None of this means that slowpath should not be improved if necessary.
> On the contrary, I would welcome good kernel profiling output from
> someone such as sim@netnation during such stress tests.
I decided to try some profiling while waiting for kernel compiles.
It seems that having a full BGP table is slowing thing down a lot.
I put 2.4.21-rc2 (with the new hash) on the test box. I modified juno
to include a busy delay loop (to try to avoid timer aliasing throwing
off the remote profile and to be short enough to generate sufficient
traffic), and tuned it to leave about 30% idle CPU on the testing box.
I fired up juno, ran "readprofile -r", and let it sit for a while.
readprofile results:
384 do_gettimeofday 2.6667
199 ipt_route_hook 3.1094
1092 fib_lookup 3.4125
1286 ip_packet_match 3.8274
248 fib_rule_put 3.8750
3209 rt_intern_hash 4.1784
852 dst_destroy 4.8409
1923 fn_hash_lookup 6.6771
1325 kmem_cache_free 8.2812
1387 dst_alloc 9.6319
3857 tg3_interrupt 11.4792
3848 do_softirq 16.0333
7354 ip_route_input 17.0231
8814 tg3_poll 28.9934
17370 handle_IRQ_event 108.5625
26413 default_idle 412.7031
I then faked a whole slew of routing table entries to look like normal
BGP routes. "ip -o route | wc -l" shows 181012 entries, which is similar
to the actual routers. readprofile results:
289 do_gettimeofday 2.0069
669 fib_lookup 2.0906
158 fib_rule_put 2.4688
367 tg3_recycle_rx 2.5486
889 ip_packet_match 2.6458
2375 rt_intern_hash 3.0924
636 dst_destroy 3.6136
868 dst_alloc 6.0278
2029 tg3_interrupt 6.0387
1037 kmem_cache_free 6.4813
5364 ip_route_input 12.4167
993 default_idle 15.5156
7593 tg3_poll 24.9770
9631 handle_IRQ_event 60.1938
26552 fn_hash_lookup 92.1944
Hmm! I guess the routing table size has a slight difference on
performance there.
Full readprofile output available here:
http://blue.netnation.com/sim/ref/
I'm not sure if this is a "good" profile or not... I can try with
oprofile or something instead if that gives more useful results.
I think I wrote a loadable module to dump the hash distribution a while
back, but I can't remember where I put it. I'll try writing something
like that again and see if there's anything interesting.
Simon-
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This archive was generated by hypermail 2b29 : Fri May 23 2003 - 22:00:03 EST