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Description of problem:
Vmstat command result shows only blocked process which are waiting for IO to get completed and not all process in 'D/UN' state however the man page of vmstat has incorrect information.
It is written as,
b: The number of processes in uninterruptible sleep.
But as per the actual result, it should be written as,
b: The number of processes blocked on IO (in uninterruptible sleep.)
Actual Result :
FIELD DESCRIPTION FOR VM MODE
Procs
r: The number of runnable processes (running or waiting for run time).
b: The number of processes in uninterruptible sleep.
Expected Result :
FIELD DESCRIPTION FOR VM MODE
Procs
r: The number of runnable processes (running or waiting for run time).
b: The number of processes blocked on IO (in uninterruptible sleep.)
^^^^^^^^^^^^^
Additional info:
FYI :
Below is the last update from bugzilla=1374332 hence opening this new documentation BZ
~~~~~~~~~~~~~~~Snippet from Bugzilla ID=1374332~~~~~~~~~~~~~~~~~~~~
I took a peek at the source for vmstat and it's interesting that in the
absence of a /proc/stat "procs_blocked" field (Linux 2.5.46
(approximately) and below), it will iterate through all /proc/<PID>/stat
files looking for 'R' or 'D' fields. In 2002 code was added to use
/proc/stat "procs_blocked" if it was available. Nothing in the commit
message for this change makes reference to this field or any change in
reporting semantics. IMHO, this was a bug introduced into vmstat long
ago... since nobody has complained in the interim, I would suggest
changing the vmstat documentation to match its current implementation:
FIELD DESCRIPTION FOR VM MODE
Procs
r: The number of runnable processes (running or waiting for run time).
b: The number of processes blocked on IO (in uninterruptible sleep.)
^^^^^^^^^^^^^
or something to the effect of explaining that the value is only the
subset of TASK_UNINTERRUPTIBLE waiting on I/O completion.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (procps-ng bug fix and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2020:4017
Description of problem: Vmstat command result shows only blocked process which are waiting for IO to get completed and not all process in 'D/UN' state however the man page of vmstat has incorrect information. It is written as, b: The number of processes in uninterruptible sleep. But as per the actual result, it should be written as, b: The number of processes blocked on IO (in uninterruptible sleep.) Actual Result : FIELD DESCRIPTION FOR VM MODE Procs r: The number of runnable processes (running or waiting for run time). b: The number of processes in uninterruptible sleep. Expected Result : FIELD DESCRIPTION FOR VM MODE Procs r: The number of runnable processes (running or waiting for run time). b: The number of processes blocked on IO (in uninterruptible sleep.) ^^^^^^^^^^^^^ Additional info: FYI : Below is the last update from bugzilla=1374332 hence opening this new documentation BZ ~~~~~~~~~~~~~~~Snippet from Bugzilla ID=1374332~~~~~~~~~~~~~~~~~~~~ I took a peek at the source for vmstat and it's interesting that in the absence of a /proc/stat "procs_blocked" field (Linux 2.5.46 (approximately) and below), it will iterate through all /proc/<PID>/stat files looking for 'R' or 'D' fields. In 2002 code was added to use /proc/stat "procs_blocked" if it was available. Nothing in the commit message for this change makes reference to this field or any change in reporting semantics. IMHO, this was a bug introduced into vmstat long ago... since nobody has complained in the interim, I would suggest changing the vmstat documentation to match its current implementation: FIELD DESCRIPTION FOR VM MODE Procs r: The number of runnable processes (running or waiting for run time). b: The number of processes blocked on IO (in uninterruptible sleep.) ^^^^^^^^^^^^^ or something to the effect of explaining that the value is only the subset of TASK_UNINTERRUPTIBLE waiting on I/O completion. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~