Per Process disk read/write statistics in Mac OS X

Question

How do I get programatically per process disk i/o statistics in Mac OS X. In 'Activity Monitor' application or in 'top' command we can only get whole system disk i/o statistics.
For reference Similar question asked for PC.

@Anoop This is part of a processor monitoring tool, not for hacking — Raviprakash, Apr 03 '13 at 12:36

score 37 · Accepted Answer · edited Nov 12 '13 at 21:57

37

Use iotop (as root), for example:

iotop -C 3 10

But the best way (for me) is:

sudo fs_usage -f filesys

edited Nov 12 '13 at 21:57

Thomas Ayoub

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answered May 08 '13 at 22:36

slerena

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very handy. iotop only showed me that mds and mdworker were hammering my disk. fs_usage showed the zillions of files in Mail.app that it was indexing, so pointed me in the right direction as to what the issue was. – ski_squaw Oct 01 '13 at 18:14
8

Note that with El Capitan, it doesn't work, as `iotop` relies on `dtrace`. And El Capitan disables `dtrace` with the rootless (SIP) mode. – bric3 Mar 17 '16 at 17:30
2

This is broken on Sierra, too. – Jul 06 '17 at 22:30

score 4 · Answer 2 · answered Aug 26 '16 at 14:21

Since there isn't an answer here about how to do this programatically, here's some more info. You can get some info out of libproc if you can use C/C++/ObjectiveC++. The function proc_pid_rusage gives you a bunch of resource info for a given process, but the ones related to your question are:

struct rusage_info_v3 {
    ...
    uint64_t ri_diskio_bytesread;
    uint64_t ri_diskio_byteswritten;
    ...
};

Sample code:

pid_t pid = 10000;
rusage_info_current rusage;
if (proc_pid_rusage(pid, RUSAGE_INFO_CURRENT, (void **)&rusage) == 0)
{
    cout << rusage.ri_diskio_bytesread << endl;
    cout << rusage.ri_diskio_byteswritten << endl;
}

See <libproc.h> and <sys/resource.h> for more info.

but proc_pid_rusage always fail with -1, and errno is 22. – holybiner Jan 09 '22 at 14:59 — holybiner, Jan 09 '22 at 14:59

score 3 · Answer 3 · answered Jul 10 '19 at 08:50

Since OP specifically asked for disk I/O statistics I'd recommend

sudo fs_usage -f diskio

which focuses only on read/write events, contrary to -f filesys as mentioned in the accepted answer. (Don't know if the diskio option wasn't available back then.)

rogerdpack · Answer 4 · 2016-11-01T16:02:23.133

2

Activity Monitor shows per process I/O statistics in the "disk" tab (perhaps its new since this question was asked). See "Bytes Written" and "Bytes Read" columns.

edited Nov 01 '16 at 16:02

answered Oct 26 '16 at 18:02

rogerdpack

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These are aggregate counts over the lifespan of the process, and do not show periodic/current statistics like top or iotop. I don't know why Apple thinks these stats are useful. People want `iotop` like functionality. – theferrit32 Feb 22 '21 at 17:46
Right, I end up just ordering by 'bytes written' etc. and manually tracking deltas with my eyes. Not programmatic at all sadly. – rogerdpack Feb 22 '21 at 21:06
Do you know how these aggregate counts are made? Is it just by constantly summing up all the small disk writes/reads? Can I access those aggregate figures with Terminal? – alexx0186 Oct 18 '22 at 00:05
@theferrit32 Why would you think aggregate counts aren't useful? If "People" want iotop output, they can use iotop. – Jake Dec 04 '22 at 21:30

score 1 · Answer 5 · answered Mar 19 '17 at 10:49

1

I found iStat Menus, which sits in the menu bar. Only shows the top 5 disk read/write users (and I'm not sure if it's the sum, but it doesn't sort).

answered Mar 19 '17 at 10:49

Quantum Mechanic

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Per Process disk read/write statistics in Mac OS X

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