>>> Martin Steigerwald <mar...@lichtvoll.de> schrieb am 02.07.2015 um 11:26 in Nachricht <1479160.a5Vb4cJSSF@merkaba>: > On Thursday 02 July 2015 10:50:13 Ulrich Windl wrote: >> Hi! > > Hi Ulrich, > >> I'm not subscribed, so plese CC: me for your replies. >> >> When graphing the CPU load, I noticed that the 15-minute average never >> drops below 0.05, while the 5-minute load and the 1-minute load does >> (Kernel 3.0.101-0.47.52-xen of SLES11 on x86_64). > > Load average is *NOT* the CPU load although this is a very common > misconception.
I think the correlation of 1-min, 5-min and 15-min values is independent of the actual meaning of the value. > > Load average indicates the amount of processes that are waiting to be > scheduled / running (which is CPU saturation) *and* those that are waiting > uninterruptable. You can have a high load average without much CPU > utilizitation, for example by running 20 find processes on a /home on NFS. > > A high load can be CPU-bound but it doesn't need to be. I knew. > > So a high load only can indicate that things are running more slowly, but > not why, or well the why can be at least two things and does not need to be > CPU. How is that related to my complaint/question? > > Also the load is normalized to CPU cores. Actually I don't think so, but that's also not related to the issue I reported. In know that HP-UX load was the average load of every CPU, while for Linux the load seemed to be the sum of all CPU loads, meaning a load of 4 is low for a 12-CPU machine. But that's all unrelated... > >> Ist that a known bug? Interactive call of "uptime" seems to confirm my >> suspect: windl> uptime >> 10:41am up 23 days 18:49, 1 user, load average: 0.08, 0.05, 0.05 >> windl> uptime >> 10:48am up 23 days 18:56, 1 user, load average: 0.00, 0.04, 0.05 >> windl> cat /proc/loadavg >> 0.00 0.04 0.05 1/108 9704 >> >> I'll attach a sample graph. > > Why should it be? As you can see in the graph you have higher spikes with 1- > minute average. As its just a average about one minute it more easily drops > below 0,05. But the 5 minute and 15 minute avergage need more time to drop > lower, so for it to become lower, you need longer times without spikes in > load average. > > So its natural you get "flatter" curves with higher average. Average easily > hide things like spikes. Actually it seems my "mathematical eye" is better than yours: I have another graph that shows the problem even more clearly (same kernel and hardware, just another machine). Regards, Ulrich
