How to Find The Processor Queue Length in Linux

How is run queue length computed in linux proc filesystem

As gcla said you cat use

cat /proc/loadavg

to read loadavarage from from kernel - but strictly speaking, it is not a queue length.

Take a look at

grep procs_running /proc/stat

and

grep procs_blocked /proc/stat

First is an actual running queue and second is a number of process blocked on disk IO. Load average is a function from sum of both.

Solaris CPU run queue

The run-queue is always changing, so it's almost impossible to get the set of processes in the current run-queue.

That said, you can get an approximation by looking at the STAT (state) field of the process list from ps. When running the command below:

$ ps aux

...the if the STAT field begins with R, then the process is marked RUNNABLE by the kernel, which on most operating systems means that it is in the run-queue. Here's what a runnable process looks like on my machine:

USER       PID %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
root     78179   0.0  0.0   599828    480 s003  R+    7:51AM   0:00.00 ps aux

On solaris, you can also use the prstat command and look at the STATE column. The value run indicates that the process is on the run-queue. (Also note that the value cpuN indicates that the process is currently running on processor N.

For example:

$ prstat -s cpu -n 5

PID USERNAME    SIZE    RSS STATE   PRI NICE    TIME    CPU PROCESS/NLWP
13974   kincaid 888K    432K    run 40  0   36:14.51    67% cpuhog/1
27354   kincaid 2216K   1928K   run 31  0   314:48.51   27% server/5
14690   root    136M    46M sleep   59  0   0:00.59 2.3%    Xsun/1
14797   kincaid 9192K   7496K   sleep   59  0   0:00.10 0.9%    dtwm/8
14851   kincaid 24M 14M sleep   48  0   0:00.03 0.3%    netscape/1
Total: 97 processes, 190 lwps, load averages: 2.18, 2.15, 2.11

How to get total cpu usage in Linux using C++

cat /proc/stat

http://www.linuxhowtos.org/System/procstat.htm

I agree with this answer above. The cpu line in this file gives the total number of "jiffies" your system has spent doing different types of processing.

What you need to do is take 2 readings of this file, seperated by whatever interval of time you require. The numbers are increasing values (subject to integer rollover) so to get the %cpu you need to calculate how many jiffies have elapsed over your interval, versus how many jiffies were spend doing work.

e.g.
Suppose at 14:00:00 you have

cpu 4698 591 262 8953 916 449 531

total_jiffies_1 = (sum of all values) = 16400

work_jiffies_1 = (sum of user,nice,system = the first 3 values) = 5551

and at 14:00:05 you have

cpu 4739 591 289 9961 936 449 541

total_jiffies_2 = 17506

work_jiffies_2 = 5619

So the %cpu usage over this period is:

work_over_period = work_jiffies_2 - work_jiffies_1 = 68

total_over_period = total_jiffies_2 - total_jiffies_1 = 1106

%cpu = work_over_period / total_over_period * 100 = 6.1%

Hope that helps a bit.

How to find the socket buffer size of linux

If you want see your buffer size in terminal, you can take a look at:

• /proc/sys/net/ipv4/tcp_rmem (for read)
• /proc/sys/net/ipv4/tcp_wmem (for write)

They contain three numbers, which are minimum, default and maximum memory size values (in byte), respectively.

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