Hi again, I have been investigating about this and I think that with top I don´t get the usage of the cpu but I get de % of the cpu of the process. I´ll explain better with and example. With the command sar I get that the cpu usage es 35%, for example, and with top I get that java is using 80% but what it is saying that the java process is using the 80% of the 35% of the cpu usage, not the 80% of the whole cpu. Do you think that my conclusion is true? BTW, is there any parameter in the system that tells the kernel the limit of cpu a process can get? Greetings, ESG 2009/11/24 ESGLinux <esggrupos@xxxxxxxxx> > Hello, > > I´m checking the performance of one RHEL running a java process and I use > the sar command and the top command to see the cpu usage and I get some > differences that I don´t understand. > > First I´ll tell you how I check it: > for the sar command I run this: > sadc -F -L 1 1000 /home/user/log/output > > for top I run this: > top -b -d 1 -n 1000 -p $PID > > PID is the PID of my java process. > > Well, when I run this I get this results: > > PM CPU %user %nice %system %iowait > %idle > 07:09:09 PM all 35.75 0.00 7.25 0.00 > 57.00 > 07:09:11 PM all 50.00 0.00 13.43 0.00 > 36.57 > 07:09:13 PM all 23.56 0.00 7.27 0.00 > 69.17 > 07:09:15 PM all 36.75 0.00 8.00 0.00 > 55.25 > 07:09:17 PM all 66.08 0.00 10.22 0.25 > 23.44 > 07:09:19 PM all 31.17 0.00 6.23 0.00 > 62.59 > > top > TIME PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 19:09:09 26314 user 16 0 817m 324m 36m S 99.9 8.6 0:44.11 java > 19:09:11 26314 user 16 0 817m 382m 36m S 99.9 10.1 0:46.70 java > 19:09:13 26314 user 16 0 817m 381m 36m S 99.9 10.1 0:48.02 java > 19:09:15 26314 user 16 0 828m 392m 36m S 99.9 10.4 0:49.95 java > 19:09:18 26314 user 16 0 817m 398m 36m S 95.8 10.6 0:52.16 java > 19:09:20 26314 user 16 0 817m 398m 36m S 51.9 10.6 0:54.20 java > > with sar I never reach the 99,9% of CPU but with top I see this amount of > CPU in several times. > > So, which is the true value of CPU usage? and why this differences? > > thanks in advance > > ESG > > > -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subjecthttps://www.redhat.com/mailman/listinfo/redhat-list
