Re: I don't get where the load comes from

> On 2011-06-01 15.12, Joel Wiramu Pauling wrote:
> > Load is generally a measure of a single processor core utilization over
> an
> > kernel dependent time range.
>
> No it isn't. You have totally misunderstood what the load average is.
>
> > Generally as others have pointed out being a very broad (not as in
> meadow,
> > as in continent). Different OS's report load very differently from each
> > other today.
>
> That one's sort of correct, although I've yet to see an OS where the load
> doesn't in some way refer to an *average* *count* *of* *processes*.
>
> > Traditionally you would see a load average of 1-2 on a multicore system
> (I
> > am talking HP-UX X client servers etc of the early 90's vintage). a Load
> > average of 1 means a single core of the system is being utilized close to
> > 100% of the time.
>
> No, no, no. Absolutely *NOT*. It doesn't reflect CPU usage at all.
>
> And it never have. The load average must be the single most misunderstood
> kernel metric there have ever been in the history of unix systems.
>
> Very simplified it reflects the *number* *of* *processes* in a runnable
> state,
> averaged over some time. Not necessarily processes actually on core,
> mind you,
> but the number of processes *wanting* to run.
>
> Now, a process can be in a runnable state for a variety of reasons, and
> there
> is for example nothing that says it even needs to use up its alloted time
> slice when actually running, but it still counts as runnable. It can be
> runnable when waiting for a system resource; then it consumes *no* CPU
> cycles
> at all, but it still counts towards the load average.
>
> > On dual core systems a load average of 1 should be absolutely no cause
> for
> > concern.
>
> I routinely see load averages of 30-40-50, upwards of 100 on some of my
> systems. They run absolutely smooth and beautiful, with no noticable lag
> or delays. The processors may be near idling, they may be doing some work,
> it varies, but it is nothing I can tell from the load average alone.
>
> > Linux has moved away from reporting load average as a percentage of a
> single
> > core time in recent days for precisely this reason, people see a load of
> 1
> > and think there systems are esploding.
> >
> > In the traditional mold todays processors should in theory get loads of
> 4-7
> > and still be responsive...
>
> I'm sorry to say, but your entire text is based on a misunderstanding of
> what
> the load average really is, so the above sentences are totally irrelevant.
>
>

> > On 31 May 2011 19:10, Joel Carnat <joel@...> wrote:
> >
> >> Le 31 mai 2011 ` 08:10, Tony Abernethy a icrit :
> >>> Joel Carnat wrote
> >>>> well, compared to my previous box, running NetBSD/xen, the same
> services
> >>>> and showing about 0.3-0.6 of load ; I thought a load of 1.21 was quite
> >> much.
> >>>
> >>> Different systems will agree on the spelling of the word load.
> >>> That is about as much agreement as you can expect.
> >>> Does the 0.3-0.6 really mean 30-60 percent loaded?
> >>
> >> As far as I understood the counters on my previous nbsd box, 0.3 meant
> that
> >> the
> >> cpu was used at 30% of it's total capacity. Then, looking at the
> sys/user
> >> counters,
> >> I'd see what kind of things the system was doing.
> >>
> >>> 1.21 tasks seems kinda low for a multi-tasking system.
> >>
> >> ok :)
> >
>
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