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boostr.in questions - Question:how to Track Down CPU-Bound Load?
If you do see a high percentage in the user or system columns, there's a good chance your load is CPU-bound. To track down the root cause, skip down a few lines to where top displays a list of current processes running on the system. By default, top will sort these based on the percentage of CPU used with the processes using the most on top (Listing 2). Listing 2. Current Processes Example PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 9463 mysql 16 0 686m 111m 3328 S 53 5.5 569:17.64 mysqld 18749 nagios 16 0 140m 134m 1868 S 12 6.6 1345:01 nagios2db_status 24636 nagios 17 0 34660 10m 712 S 8 0.5 1195:15 nagios 22442 nagios 24 0 6048 2024 1452 S 8 0.1 0:00.04 check_time.pl The %CPU column tells you just how much CPU each process is taking up. In this case, you can see that MySQL is taking up 53% of my CPU. As you look at this output during CPU-bound load, you probably will see one of two things: either you will have a single process tying up 99% of your CPU, or you will see a number of smaller processes all fighting for a percentage of CPU time. In either case, it's relatively simple to see the processes that are causing the problem. There's one final note I want to add on CPU-bound load: I've seen systems get incredibly high load simply because a multithreaded program spawned a huge number of threads on a system without many CPUs. If you spawn 20 threads on a single-CPU system, you might see a high load average, even though there are no particular processes that seem to tie up CPU time.
Sep 13, 2013
Sep 12, 2013
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