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    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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