Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q8

[Ingo Molnar]

* Lee Revell <rlrevell@xxxxxxxxxxx> wrote:

> Here are traces of a 145, 190, and 217 usec latencies in
> netif_receive_skb:
> 
> http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-Q6#/var/www/2.6.9-rc1-Q6/trace2.txt
> http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-Q6#/var/www/2.6.9-rc1-Q6/trace3.txt
> http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-Q6#/var/www/2.6.9-rc1-Q6/trace4.txt

these all seem to be single-packet processing latencies - it would be
quite hard to make those codepaths preemptible.

i'd suggest to turn off things like netfilter and ip_conntrack (and
other optional networking features that show up in the trace), they can
only increase latency:

 00000001 0.016ms (+0.000ms): ip_rcv (netif_receive_skb)
 00000001 0.019ms (+0.002ms): nf_hook_slow (ip_rcv)
 00000002 0.019ms (+0.000ms): nf_iterate (nf_hook_slow)
 00000002 0.021ms (+0.001ms): ip_conntrack_defrag (nf_iterate)
 00000002 0.022ms (+0.000ms): ip_conntrack_in (nf_iterate)
 00000002 0.022ms (+0.000ms): ip_ct_find_proto (ip_conntrack_in)
 00000103 0.023ms (+0.000ms): __ip_ct_find_proto (ip_ct_find_proto)
 00000102 0.024ms (+0.000ms): local_bh_enable (ip_ct_find_proto)
 00000002 0.025ms (+0.001ms): tcp_error (ip_conntrack_in)

	Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/