Re: [PATCH v6] net: batch skb dequeueing from softnet input_pkt_queue

[Eric Dumazet <eric.dumazet@gmail.com>]

Le dimanche 02 mai 2010 à 16:27 +0200, Eric Dumazet a écrit :
> Le dimanche 02 mai 2010 à 07:13 -0700, Arjan van de Ven a écrit :
> > > 
> > > Cn                Avg residency       P-states (frequencies)
> > > C0 (cpu running)        (68.9%)         2.93 Ghz    46.5%
> > > polling           0.0ms ( 0.0%)         2.80 Ghz     5.1%
> > > C1 mwait          0.0ms ( 0.0%)         2.53 Ghz     3.0%
> > > C2 mwait          0.0ms (31.1%)         2.13 Ghz     2.8%
> > >                                         1.60 Ghz    38.2%
> > 
> > I bet your system advertizes C2 with the same latency as C1,
> > but with lower power... which means Linux will pretty much never
> > pick C1.... no matter how much you take Andi's patch.
> > 
> > this is a bios thing... and until we put in the patch to override the
> > bios values (I can dust it off but it might need a bit of tweaking
> > since it was against .31) Andi's patch alone won't cut it... you also
> > need a non-lying bios ;)
> > 
> > 
> > 
> # pwd
> /sys/devices/system/cpu/cpu15/cpuidle
> # grep . */*
> state0/desc:CPUIDLE CORE POLL IDLE
> state0/latency:0
> state0/name:C0
> state0/power:4294967295
> state0/time:0
> state0/usage:0
> state1/desc:ACPI FFH INTEL MWAIT 0x0
> state1/latency:1
> state1/name:C1
> state1/power:1000
> state1/time:433855186
> state1/usage:126869
> state2/desc:ACPI FFH INTEL MWAIT 0x10
> state2/latency:64
> state2/name:C2
> state2/power:500
> state2/time:198095020416
> state2/usage:76287744
> 
> C2 latency seems to be 64  (us ?), while C1 seems to be 1
> 
> BIOS Information
> 	Vendor: HP
> 	Version: I24
> 	Release Date: 10/01/2009
> 
> # powertop
> PowerTOP 1.11   (C) 2007, 2008 Intel Corporation 
> 
> Collecting data for 5 seconds 
> 
> 
> Your CPU supports the following C-states : C1 C2 C3 
> Your BIOS reports the following C-states : C1 C2 
> 
> C3 seems to be disabled in BIOS
> 

I took a look at BIOS settings and enabled the minimum sleep state to be
C6 (instead of C3, the default). Now we see C3 being available...

No changes, only more IPI delivered during the test, and more overhead
in clockevents_notify()

# grep . */*
state0/desc:CPUIDLE CORE POLL IDLE
state0/latency:0
state0/name:C0
state0/power:4294967295
state0/time:0
state0/usage:0
state1/desc:ACPI FFH INTEL MWAIT 0x0
state1/latency:1
state1/name:C1
state1/power:1000
state1/time:39432
state1/usage:119
state2/desc:ACPI FFH INTEL MWAIT 0x10
state2/latency:64
state2/name:C2
state2/power:500
state2/time:3170745
state2/usage:11177
state3/desc:ACPI FFH INTEL MWAIT 0x20
state3/latency:96
state3/name:C3
state3/power:350
state3/time:1030987453
state3/usage:14047019

---------------------------------------------------------------------------------------------------------------------------
   PerfTop:   15984 irqs/sec  kernel:98.5% [1000Hz cycles],  (all, 16 CPUs)
---------------------------------------------------------------------------------------------------------------------------

             samples  pcnt function                       DSO
             _______ _____ ______________________________ _______

            23822.00 40.2% _raw_spin_lock_irqsave         vmlinux
             4413.00  7.4% acpi_os_read_port              vmlinux
             1426.00  2.4% _raw_spin_lock                 vmlinux
             1284.00  2.2% _raw_spin_unlock_irqrestore    vmlinux
             1247.00  2.1% schedule                       vmlinux
             1137.00  1.9% bnx2x_rx_int                   vmlinux
              643.00  1.1% tick_broadcast_oneshot_control vmlinux
              597.00  1.0% copy_user_generic_string       vmlinux
              595.00  1.0% __napi_complete                vmlinux
              550.00  0.9% call_function_single_interrupt vmlinux
              548.00  0.9% bnx2x_msix_fp_int              vmlinux
              486.00  0.8% __netif_receive_skb            vmlinux
              461.00  0.8% bnx2x_poll                     vmlinux
              433.00  0.7% eth_type_trans                 vmlinux
              428.00  0.7% acpi_idle_enter_bm             vmlinux
              422.00  0.7% sock_recv_ts_and_drops         vmlinux
              382.00  0.6% __udp4_lib_lookup              vmlinux
              369.00  0.6% __slab_free                    vmlinux
              357.00  0.6% ip_route_input                 vmlinux
              341.00  0.6% kfree                          vmlinux
              335.00  0.6% ipt_do_table                   vmlinux
              334.00  0.6% ip_rcv                         vmlinux
              332.00  0.6% udp_recvmsg                    vmlinux
              317.00  0.5% __kmalloc_node_track_caller    vmlinux

    37.46%            init  [kernel.kallsyms]             [k] _raw_spin_lock_irqsave
                      |
                      --- _raw_spin_lock_irqsave
                         |          
                         |--95.58%-- clockevents_notify
                         |          lapic_timer_state_broadcast
                         |          acpi_idle_enter_bm
                         |          cpuidle_idle_call
                         |          cpu_idle
                         |          start_secondary
                         |          
                         |--3.27%-- tick_broadcast_oneshot_control
                         |          tick_notify
                         |          notifier_call_chain
                         |          __raw_notifier_call_chain
                         |          raw_notifier_call_chain
                         |          clockevents_do_notify
                         |          clockevents_notify
                         |          lapic_timer_state_broadcast
                         |          acpi_idle_enter_bm