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Date
From
SubjectRe: Measuring tools - top and interrupts


--- Mike Galbraith <efault@gmx.de> wrote:
> 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
>
Thats a pretty crappy controller you have in with
that shiny P4...

I'm not sure that they want the tools to work.
They'll just call you a troll and go on
developing unnecessary things like NAPI because
they're still using controllers designed by DEC
(remember them?) back in the stone ages.

Yet I regularly encounter people using cheap NICs
with expensive cpus on network-intensive
applications. But you'd think one or two people
would have a clue.

DT

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