From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: 0% cpu usasge after fresh boot or net restart but 10% CPU if
 kernel flush route cache
Date: Thu, 28 Jan 2010 17:09:17 +0100
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Le jeudi 28 janvier 2010 =C3=A0 11:14 +0200, cold cold a =C3=A9crit :

>=20
> RX Kpps : 57 TX Kpps : 53  RX Kbits : 331184 TX Kbits : 306213
> RX Kpps : 59 TX Kpps : 54  RX Kbits : 345517 TX Kbits : 304323
> RX Kpps : 56 TX Kpps : 52  RX Kbits : 331418 TX Kbits : 296032
> RX Kpps : 60 TX Kpps : 54  RX Kbits : 362007 TX Kbits : 297371
> RX Kpps : 59 TX Kpps : 52  RX Kbits : 360455 TX Kbits : 280603
>=20
>=20
> ON  one cpu, gc_interval to 1, gc_elasticity 2
>=20
> Cpu0  :  0.0%us,  0.0%sy,  0.0%ni, 72.0%id,  0.0%wa,  8.3%hi, 19.7%si=
,  0.0%st
> Cpu1  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si=
,  0.0%st
> Cpu2  :  0.0%us,  0.3%sy,  0.0%ni, 99.7%id,  0.0%wa,  0.0%hi,  0.0%si=
,  0.0%st
> Cpu3  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si=
,  0.0%st
>=20
> ---------------------------------------------------------------------=
---------
>    PerfTop:   17064 irqs/sec  kernel:98.0% [100000 cycles],  (all, 4 =
CPUs)
> ---------------------------------------------------------------------=
---------
>=20
>              samples    pcnt   kernel function
>              _______   _____   _______________
>=20
>             40388.00 - 27.8% : acpi_idle_do_entry
>             24651.00 - 17.0% : read_hpet
>              4271.00 -  2.9% : _spin_lock
>              3388.00 -  2.3% : pskb_expand_head
>              3288.00 -  2.3% : igb_poll [igb]
>              3246.00 -  2.2% : irq_entries_start
>              2868.00 -  2.0% : dev_gro_receive
>              2665.00 -  1.8% : igb_xmit_frame_adv       [igb]
>              2513.00 -  1.7% : ip_route_input
>              2144.00 -  1.5% : igb_clean_tx_irq [igb]
>              1842.00 -  1.3% : __slab_free
>              1544.00 -  1.1% : dev_queue_xmit
>              1423.00 -  1.0% : igb_msix_rx      [igb]
>              1353.00 -  0.9% : __alloc_skb
>              1285.00 -  0.9% : eth_type_trans
> --

All this seems pretty normal profile (regarding networking functions),
your machine should scale without problem.

Of course, the two first functions (acpi_idle_do_entry() & read_hpet())
look suspicious but I have no idea why.