cset-shield(1)
==============
Alex Tsariounov <tsariounov@gmail.com>
v1.6, December 2018

NAME
----
cset-shield - cpuset supercommand which implements cpu shielding

SYNOPSIS
--------
[verse]
'cset' [cset options] 'shield' [shield options] [args]
'cset' shield --help
'cset' shield
'cset' shield --cpu 1-7
'cset' shield --cpu 1-7 --kthread=on
'cset' shield --exec /opt/software/myapp/doit --my_opt1 --my_opt2
'cset' shield --user appuser --exec run_benchmark.sh
'cset' shield --shield --pid 1024,2048,5000-1000
'cset' shield --unshield --pid 6000-8500
'cset' shield --kthread=off
'cset' shield --kthread=on
'cset' shield --shield bash

OPTIONS
-------
-h, --help::
  prints the list of options for this command

-c CPUSPEC, --cpu=CPUSPEC::
  modifies or initializes the shield cpusets

-r, --reset::
  destroys the shield

-e, --exec::
  executes args in the shield

--user=USER::
  use this USER for --exec (id or name)

--group=GROUP::
  use this GROUP for --exec (id or name)

-s, --shield::
  shield PIDSPEC specified with -p/--pid of processes or threads

-u, --unshield::
  remove PIDSPEC specified with -p/--pid of processes or threads from
  the shield, the tasks keep running in the unshielded cpuset

--threads::
  if specified, any processes found in the PIDSPEC to have multiple
  threads will automatically have all their threads added to the 
  PIDSPEC (use to shield or unshield all related threads)

-k on|off, --kthread=on|off::
  shield from unbound interrupt threads as well

-f, --force::
  force operation, use with care

-v, --verbose::
  prints more detailed output, additive

--sysset=SYSSET::
  optionally specify system cpuset name

--userset=USERSET::
  optionally specify user cpuset name

DESCRIPTION
-----------
This is a supercommand that creates basic cpu shielding.  The
normal cset commands can of course be used to create this basic
shield, but the shield command combines many such commands to
create and manage a common type of cpu shielding setup.

The concept of shielding implies at minimum three cpusets, for
example: root, user and system.  The root cpuset always exists in
all implementations of cpusets and contains all available CPUs on
the machine.  The system cpuset is so named because normal system
tasks are made to run on it.  The user cpuset is so named because
that is the "shielded" cpuset on which you would run your tasks
of interest.

Usually, CPU zero would be in the system set and the rest of the
CPUs would be in the user set.  After creation of the cpusets,
all processes running in the root cpuset are moved to the system
cpuset.  Thus any new processes or threads spawned from these
processes will also run the system cpuset.

If the optional --kthread=on option is given to the shield
command, then all kernel threads (with exception of the per-CPU
bound interrupt kernel threads) are also moved to the system set.

One executes processes on the shielded user cpuset with the
--exec subcommand or moves processes or threads to the shielded
cpuset with the --shield subcommand with a --pid option.  

NOTE: You do not need to specify which cpuset a process or thread
is running in initially when using the --shield subcommand.

To create a shield, you would execute the shield command with the
--cpu option that specifies CPUSPEC argument that assigns CPUs to
be under the shield (this means assigned to the user cpuset, all
other cpus will be assigned to the system set).

For example:

*+# cset shield --cpu=1-3+*

On a 4-way machine, this command will dedicate the first
processor, CPU0, for the system set (unshielded) and  the last
three processors, CPU1, CPU2, CPU3, for the user set (shielded).

The CPUSPEC will accept a comma separated list of CPUs and
inclusive range specifications.   For example, --cpu=1,3,5-7 will
assign CPU1, CPU3, CPU5, CPU6, and CPU7 to the user (or shielded)
cpuset and the inverse of that to the system (or unshielded)
cpuset.

If you do not like the names "system" and "user" for the
unshielded and shielded sets respectively, or if those names are
used already, then use the --sysset and --userset options.

For example:

*+# cset shield --sysset=free --userset=cage --cpu=2,3 --kthread=on+*

The above command will use the name "free" for the unshielded
system cpuset, the name "cage" for the shielded user cpuset,
initialize these cpusets and dedicate CPU0 and CPU1 to the "free"
set and (on a 4-way machine) dedicate CPU2 and CPU3 to the "cage"
set.  Further, the command moves all processes and threads,
including kernel threads from the root cpuset to the "free"
cpuset.  

NOTE: If you do use the --sysset/--userset options, then you must
continue to use those for every invocation of the shield supercommand.

After initialization, you can run the process of interest on the
shielded cpuset with the --exec subcommand, or move processes or
threads already running to the shielded cpuset with the --shield
subcommand and the --pid option.

Note that if your execed command takes options, then use the
traditional "--" marker to separate cset's options from your
command's options.

For example:

*+# cset shield --exec -- ls -l+*

This command will execute "ls -l" inside the shield.

The PIDSPEC argument taken for the --pid (or -p) option is a
comma separated list of PIDs or TIDs.  The list can also include
brackets of PIDs or TIDs that are inclusive of the endpoints.

For example:

    1,2,5               Means processes 1, 2 and 5
    1,2,600-700         Means processes 1, 2 and from 600 to 700

*+# cset shield --shield --pid=50-65+*

The above command moves all processes and threads with PID or TID
in the range 50-65 inclusive, from the system cpuset into the
shielded user cpuset.  If they are running in the root cpuset,
you must use the --force option to actually move them into the
shield.

NOTE: The range of PIDs or TIDs does not need to have every
position populated.  In other words, for the example above, if
there is only one process, say PID 57, in the range of 50-65,
then only that process will be moved.

The --unshield (or -u) subcommand will remove the specified
processes or threads from the shielded cpuset and move them into
the unshielded (or system) cpuset.  This command is also used in
conjunction with a -p/--pid option that specifies a PIDSPEC
argument, the same as for the --shield subcommand.

Both the --shield and the --unshield commands will also finally
output the number of tasks running in the shield and out of the
shield if you do not specify a PIDSPEC with --pid.  By specifying
also a --verbose in addition, then you will get a listing of
every task that is running in either the shield or out of the
shield.

Using no subcommand, ie. only "cset shield", will output the
status of both shield and non-shield.  Tasks will be listed if
--verbose is used.

You can adjust which CPUs are in the shielded cpuset by issuing
the --cpu subcommand again anytime after the shield has been
initialized.

For example if the original shield contained CPU0 and CPU1 in the
system set and CPU2 and CPU3 in the user set, if you then issue
the following command:

*+# cset shield --cpu=1,2,3+*

then that command will move CPU1 into the shielded "user" cpuset.
Any processes or threads that were running on CPU1 that belonged
to the unshielded "system" cpuset are migrated to CPU0 by the
system.

The --reset subcommand will in essence destroy the shield.  For
example, if there was a shield on a 4-way machine with CPU0 in
system and CPUs 1-3 in user with processes running on the user
cpuset (i.e. in the shield), and a --reset subcommand was issued,
then all processes running in both system and user cpusets would
be migrated to the root cpuset (which has access to all CPUs and
never goes away), after which both system and user cpusets would
be destroyed.

NOTE: Even though you can mix general usage of cpusets with
the shielding concepts described here, you generally will not
want to.  For more complex shielding or usage scenarios, one
would generally use the normal cpuset commands (i.e. cset set
and proc) directly.

LICENSE
-------
Cpuset is licensed under the GNU GPL V2 only.

COPYRIGHT
---------
Copyright (c) 2008-2011 Novell Inc.

AUTHOR
------
Written by Alex Tsariounov <\tsariounov@gmail.com>.

SEE ALSO
--------
cset(1), cset-set(1), cset-proc(1)

/usr/share/doc/packages/cpuset/html/tutorial.html

taskset(1), chrt(1)

/usr/src/linux/Documentation/cpusets.txt
