netdev - Re: 0% cpu usasge after fresh boot or net restart but 10% CPU if kernel flush route cache

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Message-ID: <1264698380.2930.20.camel@edumazet-laptop>
Date:	Thu, 28 Jan 2010 18:06:20 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	cold cold <nedkonedev@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: 0% cpu usasge after fresh boot or net restart but 10% CPU if 
 kernel flush route cache

Le jeudi 28 janvier 2010 à 18:26 +0200, cold cold a écrit :
> On Thu, Jan 28, 2010 at 6:09 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > Le jeudi 28 janvier 2010 à 11:14 +0200, cold cold a écrit :
> >
> >>
> >> 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
> >>
> >>
> >> ON  one cpu, gc_interval to 1, gc_elasticity 2
> >>
> >> 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
> >>
> >> ------------------------------------------------------------------------------
> >>    PerfTop:   17064 irqs/sec  kernel:98.0% [100000 cycles],  (all, 4 CPUs)
> >> ------------------------------------------------------------------------------
> >>
> >>              samples    pcnt   kernel function
> >>              _______   _____   _______________
> >>
> >>             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.
> >
> 
> i make with flushing without gc on 2 cpu  2 time more traffic  and CPU
> usage about 5 times less
> 
> top - 11:22:04 up  6:45,  5 users,  load average: 0.00, 0.10, 0.25
> Tasks:  84 total,   1 running,  83 sleeping,   0 stopped,   0 zombie
> Cpu0  :  0.0%us,  0.3%sy,  0.0%ni, 94.0%id,  0.0%wa,  1.7%hi,  4.0%si,  0.0%st
> Cpu1  :  0.3%us,  0.0%sy,  0.0%ni, 97.7%id,  0.0%wa,  0.7%hi,  1.3%si,  0.0%st
> Cpu2  :  0.0%us,  0.0%sy,  0.0%ni,100.0%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
> 

pure luck I guess, since you use two cpus here instead of one, but
nothing guarantee this.

> 
> RX Kpps : 90 TX Kpps : 75  RX Kbits : 582791 TX Kbits : 413873
> RX Kpps : 87 TX Kpps : 74  RX Kbits : 546327 TX Kbits : 415852
> RX Kpps : 87 TX Kpps : 74  RX Kbits : 544820 TX Kbits : 418339
> RX Kpps : 88 TX Kpps : 73  RX Kbits : 569143 TX Kbits : 406438
> --

Not sure I understand your goals. Previous numbers were with less
trafic ?

What do you want ? your cpus being idle, or your router being able to
forward packets without drops ?

Good, but if you drop packets when real garbage collection is done, you
loose. Make your choice :)



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