Re: Loopback performance from kernel 2.6.12 to 2.6.37

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

Le mardi 09 novembre 2010 à 17:30 +1100, Andrew Hendry a écrit :
> most my slowdown was kmemleak left on.
> 
> After fixing its is still a lot slower than your dev system
> .
> # time dd if=/dev/zero bs=1M count=10000 | netcat  127.0.0.1 9999
> 10000+0 records in
> 10000+0 records out
> 10485760000 bytes (10 GB) copied, 25.8182 s, 406 MB/s
> 
> real	0m25.821s
> user	0m1.502s
> sys	0m33.463s
> 
> ------------------------------------------------------------------------------------------------------------------
>    PerfTop:     241 irqs/sec  kernel:56.8%  exact:  0.0% [1000Hz
> cycles],  (all, 8 CPUs)
> ------------------------------------------------------------------------------------------------------------------
> 
>              samples  pcnt function                    DSO
>              _______ _____ ___________________________
> ______________________________________
> 
>              1255.00  8.7% hpet_msi_next_event
> /lib/modules/2.6.37-rc1+/build/vmlinux
>              1081.00  7.5% copy_user_generic_string
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               863.00  6.0% __ticket_spin_lock
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               498.00  3.5% do_sys_poll
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               455.00  3.2% system_call
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               409.00  2.8% fget_light
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               348.00  2.4% tcp_sendmsg
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               269.00  1.9% fsnotify
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               258.00  1.8% _raw_spin_unlock_irqrestore
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               223.00  1.6% _raw_spin_lock_irqsave
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               203.00  1.4% __clear_user
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               184.00  1.3% tcp_poll
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               178.00  1.2% vfs_write
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               165.00  1.1% tcp_recvmsg
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               152.00  1.1% pipe_read
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               149.00  1.0% schedule
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               135.00  0.9% rw_verify_area
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               135.00  0.9% __pollwait
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               130.00  0.9% __write
> /lib/libc-2.12.1.so
>               127.00  0.9% __ticket_spin_unlock
> /lib/modules/2.6.37-rc1+/build/vmlinux
>               126.00  0.9% __poll
> /lib/libc-2.12.1.so
> 
> 


Hmm, your clock source is HPET, that might explain the problem on a
scheduler intensive workload.

My HP dev machine
# grep . /sys/devices/system/clocksource/clocksource0/*
/sys/devices/system/clocksource/clocksource0/available_clocksource:tsc hpet acpi_pm 
/sys/devices/system/clocksource/clocksource0/current_clocksource:tsc

My laptop:
$ grep . /sys/devices/system/clocksource/clocksource0/*
/sys/devices/system/clocksource/clocksource0/available_clocksource:tsc hpet acpi_pm 
/sys/devices/system/clocksource/clocksource0/current_clocksource:tsc