[dtrace-discuss] dtrace wired issue

James C. McPherson
Mon, 14 Jan 2008 13:22:58 -0000

Aubrey Li wrote:
> On Jan 14, 2008 8:52 PM, Sean McGrath - Sun Microsystems Ireland
> <sean.mcgrath at sun.com> wrote:
>> Aubrey Li stated:
>> < Every first time to run dtrace command after the system boot up,
>> < It takes a very long time to get response.
>> < But the second time is OK, as follows:
>> <
>> < # time dtrace -l > /dev/null
>> <
>> < real    4m8.011s
>> < user    0m0.116s
>> < sys     0m2.420s
>>
>>   This first time is probably when the kernel is loading the dtrace
modules.
>>   Though still seems slow, 4 minutes.
>>     What kind of system (cpu speed etc) is the machine ?
>
> # psrinfo -vp
> The physical processor has 2 virtual processors (0 1)
>   x86 (GenuineIntel 10674 family 6 model 23 step 4 clock 2400 MHz)
>         Intel(r) CPU                  @ 2.40GHz
>
> So, I failed to understand the modules loading needs 4 minutes.


If you run "dtrace -l" with no args, *every* single loadable
module on the system will be loaded, interrogated by dtrace
and then unloaded if possible.

All those attach()es and detach()es need time, as does the
probe collation.



James C. McPherson
--
Senior Kernel Software Engineer, Solaris
Sun Microsystems
http://blogs.sun.com/jmcp	http://www.jmcp.homeunix.com/blog