lkml.org 
[lkml]   [2011]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 0/3] kvm tool: Serial emulation overhaul

btw., i just noticed another performance weirdness, running the
latest version on -tip with such a 64-bit x86 kernel:

make defconfig
make kvmconfig # sidenote: sigh - this still needs a 'make oldconfig'


and do a 'kvm run' into a shell, then I get a permanently busy
kvm executable sucking up CPU time:

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
28206 mingo 20 0 3586m 80m 1080 S 56.1 0.7 0:13.83 kvm
29462 mingo 20 0 15380 1392 900 R 0.3 0.0 0:00.02 top

perf kvm top suggests simple idling around of 16 CPUs:

--------------------------------------------------------------------------------------------------
PerfTop: 1635 irqs/sec kernel:91.1% us: 0.3% guest kernel: 8.5% guest us: 0.0% exact: 0.0% [1000Hz cycles], (all, 16 CPUs)
--------------------------------------------------------------------------------------------------
samples pcnt function DSO
_______ _____ _________________________ _______________________________
155.00 17.9% apic_timer_interrupt /home/mingo/linux/linux/vmlinux
89.00 10.3% find_busiest_group /home/mingo/linux/linux/vmlinux
66.00 7.6% native_apic_mem_write /home/mingo/linux/linux/vmlinux
51.00 5.9% idle_cpu /home/mingo/linux/linux/vmlinux
29.00 3.3% __rcu_pending /home/mingo/linux/linux/vmlinux
25.00 2.9% run_posix_cpu_timers /home/mingo/linux/linux/vmlinux
24.00 2.8% _raw_spin_lock /home/mingo/linux/linux/vmlinux
19.00 2.2% cpumask_next_and /home/mingo/linux/linux/vmlinux
19.00 2.2% ktime_get /home/mingo/linux/linux/vmlinux
18.00 2.1% run_timer_softirq /home/mingo/linux/linux/vmlinux
16.00 1.8% run_rebalance_domains /home/mingo/linux/linux/vmlinux
16.00 1.8% native_sched_clock /home/mingo/linux/linux/vmlinux
15.00 1.7% rcu_exit_nohz /home/mingo/linux/linux/vmlinux
14.00 1.6% tick_nohz_stop_sched_tick /home/mingo/linux/linux/vmlinux
14.00 1.6% hrtimer_run_queues /home/mingo/linux/linux/vmlinux

NO_HZ is set in the .config.

Btw., 'perf kvm' is in need of some love: for example it is
unable to pick up a vmlinux from the current directory and
./vmlinux does not work either, it needs
/home/mingo/linux/linux/vmlinux specified explicitly - that
sucks.

Ideally perf could be taught to talk to the guest kvm process
and get its vmlinux home position (even better: its guest
kallsyms) from there - so if i typed 'perf kvm top' it would do
the right thing all automagically. [ What a fantastc level of
automation! ;-) ]

Thanks,

Ingo


\
 
 \ /
  Last update: 2011-12-11 11:51    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site