Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q5

Lee Revell
2004-09-01T01:43:52Z

On Mon, 2004-08-30 at 05:06, Ingo Molnar wrote:
> i've uploaded -Q5 to:
>
> http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.9-rc1-bk4-Q5

This is with netdev_max_backlog = 1:

preemption latency trace v1.0.2
-------------------------------
latency: 386 us, entries: 328 (328)
-----------------
| task: ksoftirqd/0/2, uid:0 nice:-10 policy:0 rt_prio:0
-----------------
=> started at: tcp_delack_timer+0x1c/0x1d0
=> ended at: tcp_delack_timer+0x127/0x1d0
=======>
00000001 0.000ms (+0.000ms): tcp_delack_timer (run_timer_softirq)
00000001 0.000ms (+0.000ms): __sk_stream_mem_reclaim (tcp_delack_timer)
00000001 0.004ms (+0.003ms): tcp_v4_do_rcv (tcp_delack_timer)
00000001 0.005ms (+0.001ms): tcp_rcv_established (tcp_v4_do_rcv)
00000001 0.007ms (+0.001ms): __tcp_checksum_complete_user (tcp_rcv_established)
00000001 0.008ms (+0.000ms): skb_checksum (__tcp_checksum_complete_user)
00000001 0.018ms (+0.010ms): tcp_ack (tcp_rcv_established)
00000001 0.019ms (+0.001ms): tcp_ack_update_window (tcp_ack)
00000001 0.021ms (+0.001ms): tcp_urg (tcp_rcv_established)
00000001 0.021ms (+0.000ms): tcp_data_queue (tcp_rcv_established)
00000001 0.023ms (+0.001ms): sk_stream_mem_schedule (tcp_data_queue)

...

00000103 0.377ms (+0.000ms): skb_release_data (kfree_skbmem)
00000103 0.378ms (+0.000ms): kfree (kfree_skbmem)
00000103 0.379ms (+0.000ms): kmem_cache_free (kfree_skbmem)
00000103 0.383ms (+0.004ms): qdisc_restart (dev_queue_xmit)
00000103 0.384ms (+0.000ms): pfifo_fast_dequeue (qdisc_restart)
00000102 0.384ms (+0.000ms): local_bh_enable (dev_queue_xmit)
00000001 0.386ms (+0.001ms): sub_preempt_count (tcp_delack_timer)
00000001 0.387ms (+0.000ms): _mmx_memcpy (check_preempt_timing)
00000001 0.387ms (+0.000ms): kernel_fpu_begin (_mmx_memcpy)

Also, I do not get the packet loss/timeout problems that another poster
reported when setting this to 1. The network works normally, it just
does not affect the latency at all.

Full trace:

http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-Q5#/var/www/2.6.9-rc1-Q5/trace5.txt

Lee