Re: Measuring tools - top and interrupts

From: Mike Galbraith
Date: Fri Jun 23 2006 - 04:27:26 EST


On Thu, 2006-06-22 at 16:37 -0700, Danial Thom wrote:
> I'm sorry, but you're being an idiot if you think
> that 16K interrupts per second and forwarding 75K
> pps generate no cpu load. Its just that simple.
> It also means that you've never profiled a kernel
> because you don't understand where the loads are
> generated. You've probably been on too many lists
> with too many people who have no idea what
> they're talking about.

(what horrid manners)

Hm. You may be right about the load average calculation being broken.

Below is a 100 second profile sample of my 3GHz P4 handling 15K
interrupts per second while receiving a flood ping. My interpretation
is that tools should be showing ~10% cpu load rather than zero. Am I'm
misinterpreting it?

97574 total 0.0258
89549 default_idle 1017.6023
1734 ioread16 36.8936
1138 ioread8 24.7391
974 rhine_start_tx 1.3994
534 __do_softirq 3.8417
331 handle_IRQ_event 3.2772
223 rhine_interrupt 0.0739
222 memset 7.9286
194 nf_iterate 1.5520
140 local_bh_enable 1.0769
99 __kmalloc 1.0532
92 net_rx_action 0.2000
85 kfree 0.9884
82 skb_release_data 0.6406
77 csum_partial_copy_generic 0.3105
73 ip_push_pending_frames 0.0681
71 __alloc_skb 0.2898
69 kmem_cache_free 1.3529
66 kmem_cache_alloc 1.3750
62 csum_partial 0.2153
61 rt_hash_code 0.4959
61 ip_append_data 0.0253
60 netif_receive_skb 0.0516
58 ip_rcv 0.0471
58 ip_local_deliver 0.0854
58 eth_type_trans 0.2489
55 ip_output 0.0957
52 icmp_reply 0.1187


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