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Re: 80-85% of CPU time is used from the kernel in a machine that no program is running. Why?
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From: Thanasis <ski...@gm...> - 2010-09-19 19:10:15
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On Sun, Sep 19, 2010 at 9:35 PM, Maucci, Cyrille <cyr...@hp...>wrote: > Hello, > > first, you should run top or sar with refresh every 1 sec, during a long > period, first when oprofile is not started and also when it is running. > For top, you should hit the '1' key to see the per-CPU breakdown. > I did it. All the CPUs seem to be idle. I can see only 1% usage from top or sshd some times and 2% from oprofile.. Nothing more. > > Then you should look not only at the CPUs but the hottest processes. > > ++Cyrille > > > ------------------------------ > *From:* ski...@gm... [mailto:ski...@gm...] *On Behalf > Of *Petsas Athanasios > *Sent:* Sunday, September 19, 2010 8:33 PM > *To:* Maucci, Cyrille > *Cc:* opr...@li... > *Subject:* Re: 80-85% of CPU time is used from the kernel in a machine > that no program is running. Why? > > > > > > On Sun, Sep 19, 2010 at 9:22 PM, Maucci, Cyrille <cyr...@hp...>wrote: > >> Hello, >> >> why do you say no programis running? >> Didn't you mean that yourself had launched no program, but have you >> already looked at what an 'idle' system does? >> > > > Yes, I mean that I have not launched any program > >> >> From my perspective, performance troubleshooting is a drill down approach >> and oprofile is already a low-level thing. >> Before running oprofile, have you looked your idle system at a much higher >> level, like what does top or sar report? >> > > Yes I have done it. The top shows that all the cores of the machine are > idle: > > > > top - 14:28:30 up 87 days, 3:59, 1 user, load average: 0.00, 0.00, 0.00 > Tasks: 90 total, 1 running, 89 sleeping, 0 stopped, 0 zombie > Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, > 0.0%st > Mem: 2052152k total, 1117572k used, 934580k free, 260452k buffers > Swap: 6008268k total, 14464k used, 5993804k free, 445756k cached > >> >> You would probably be surprised. >> >> ++Cyrille >> >> ------------------------------ >> *From:* Thanasis [mailto:ski...@gm...] >> *Sent:* Sunday, September 19, 2010 8:12 PM >> *To:* opr...@li... >> *Subject:* 80-85% of CPU time is used from the kernel in a machine that >> no program is running. Why? >> >> Hello, >> >> I made a profiler in a machine with ubuntu os where no program was >> running, I >> started it, and after aome minutes I dumped the statistics. The results of >> the >> oreport are: >> >> root@gen1:~# opreport --exclude-dependent --demangle=smart --symbols | >> head >> warning: /no-vmlinux could not be found. >> >> CPU: Core 2, speed 2659.99 MHz (estimated) >> Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit >> mask of 0x00 (Unhalted core cycles) count 100000 >> samples % app name symbol name >> 29322 85.6042 no-vmlinux (no symbols) >> 2993 8.7379 python2.5 (no symbols) >> 991 2.8932 libc-2.8.90.so (no symbols) >> 330 0.9634 ld-2.8.90.so (no symbols) >> 124 0.3620 oprofiled (no symbols) >> 92 0.2686 libdbus-1.so.3.4.0 (no symbols) >> 90 0.2628 libglib-2.0.so.0.1800.2 (no symbols) >> ... >> ... >> >> I run the profiler again: >> >> root@gen1:~# opreport --exclude-dependent --demangle=smart --symbols | >> head >> warning: /no-vmlinux could not be found. >> CPU: Core 2, speed 2659.99 MHz (estimated) >> Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit >> mask of 0x00 (Unhalted core cycles) count 100000 >> samples % app name symbol name >> 16227 79.4040 no-vmlinux (no symbols) >> 2978 14.5723 python2.5 (no symbols) >> 671 3.2834 libc-2.8.90.so (no symbols) >> 240 1.1744 ld-2.8.90.so (no symbols) >> 60 0.2936 libdbus-1.so.3.4.0 (no symbols) >> 47 0.2300 libglib-2.0.so.0.1800.2 (no symbols) >> 39 0.1908 oprofiled (no symbols) >> ... >> ... >> >> My question is: Why the 80-85% of the CPU time is used from >> the kernel (no-vmlinux) since no program is running in this machine? >> >> Anyone that can help me please? >> >> Thank you in advance, >> Thanasis Petsas >> > > |