user:sys time ratio
Poul-Henning Kamp
phk at phk.freebsd.dk
Sun Nov 30 06:38:56 PST 2003
In message <5.0.2.1.1.20031130143248.020dc740 at popserver.sfu.ca>, Colin Percival
writes:
>At 15:30 30/11/2003 +0100, Poul-Henning Kamp wrote:
>>In message <5.0.2.1.1.20031130140203.031e8d08 at popserver.sfu.ca>, Colin
>>Percival
>> writes:
>> > When running `make buildworld`, I see large amounts of sys time; eg, 27
>> >minutes user & 14 minutes sys for building 5.2, or 14 minutes user & 10
>> >minutes sys for building 4.9. I expected the ratio of user:sys to be much
>> >larger than this, and mailing list traffic indicates that a 4:1 ratio is
>> >typical.
> >I've seen UNIX systems have "typical" system/user splits from 1/9 to 9/1
>>it all depends on what you're doing.
>
> Sure, but buildworld is a fairly well-defined benchmark; I wouldn't
>expect to see such a large difference when running exactly the same code on
>different systems.
The amount of system time depends on a lot of environmental factors.
For instance on my amd64/SMP, the vnode pool is mis-sized, so the the
namecache does not reflect what is actually already in RAM. The result
is a fair bit of system time wasted instantiating vnodes from cached
inode diskblocks.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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