How can we get IO utilization for Process by Process ID using /proc directory?

Question

iostat screenshot

I need to IO utilization for Process by Process ID without using any tool like iostat,iotop etc.

Can any please help me to get IO utilization using info files using /proc/PID?

Thanks in ADV.

And why don't you want to use any of the standard tools for this? — ewwhite, Mar 08 '16 at 12:26
Thanks ewwhite. I dont want to use any tool and i want to know the core process of calculating IO utilization of any process. — Monti Chandra, Mar 09 '16 at 04:58
You could take a look at the source code for one or more of the tools to get this type of information. — mdpc, Mar 10 '16 at 15:38

score 3 · Answer 1 · edited Jul 17 '22 at 08:28

You can get the io stats by process from proc. The information is available under /proc/[PID]/io

The information is stored like this:

cat /proc/2039/io

rchar: 293898605
wchar: 63376205
syscr: 114996
syscw: 51573
read_bytes: 98484224
write_bytes: 29159424
cancelled_write_bytes: 8192

The definitions of the fields are:

rchar: number of bytes the process read, using any read-like system call (from files, pipes, tty...).

wchar: number of bytes the process wrote using any write-like system call.

syscr: number of read-like system call invocations that the process performed.

syscw: number of write-like system call invocations that the process performed.

read_bytes: number of bytes the process directly read from disk.

write_bytes: number of bytes the process originally dirtied in the page-cache (assuming they will go to disk later).

cancelled_write_bytes: number of bytes the process "un-dirtied" - e.g. using an "ftruncate" call that truncated pages from the page-cache.

source

For further information on /proc/[pid]/io, take a look at the documentation or this Stack Overflow Q&A.

If you want to calculate the utilization you will also need stats from /proc/diskstats. The definition of the fields is defined in the Kernel documentation.

However as you can see /proc/diskstats users different metrics from /proc/[PID]/io which means you will need a lot of calculation to get utilization metrics. That is why I don't think it is a very fruitful idea to calculate these metrics manually.

Thanks knowhy,How can we get IO utilization(%) for Process by Process ID using cat /proc/2039/io? — Monti Chandra, Mar 09 '16 at 05:01

How can we get IO utilization for Process by Process ID using /proc directory?

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