12-26-2010
Yes, disk space, swap space, swap rate are still challenges. I wish they would focus on making priority and sharing more intelligent in the kernel. For instance, if the system seems to be thrashing, then a "max pages owned by any process" limit could be lowered just enough to make the page generators write over their own pages while leaving a reasonable working set for the rest. If a page like a library is disowned by a process, another process may roll it back in and own it to the benefit of the heavy user, but you still do not need to choke it past that. It might be a process with a big working set, bigger than RAM, and giving it most to RAM, but not all, is good. Something like a big sort!
I wish there were separate queues for every priority/nice at every resource, so a nice -19 job can beat on disk as hard as it wants and still leave the door open for more prioritized jobs. Of course, if you want to do disk I/O on a spindle/arm that is reading for someone else, that is a modest delay on every I/O, and some devices have deep internal queues not prioritized.
For swap, you usually want the hammer to fall on a relatively recent piggy app.: less likely approved for so much swap, more relief than small proc's, but I suppose you might have to bundle proc's by terminal and then id to deal with the accidental wave of mosquitoes sort of swap problem. Maybe some sort of slow fork for groups that get too busy, not kills!
Last edited by DGPickett; 12-26-2010 at 02:14 PM..
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LEARN ABOUT REDHAT
swapon
SWAPON(8) Linux Programmer's Manual SWAPON(8)
NAME
swapon, swapoff - enable/disable devices and files for paging and swapping
SYNOPSIS
/sbin/swapon [-h -V]
/sbin/swapon -a [-v] [-e]
/sbin/swapon [-v] [-p priority] specialfile ...
/sbin/swapon [-s]
/sbin/swapoff [-h -V]
/sbin/swapoff -a
/sbin/swapoff specialfile ...
DESCRIPTION
Swapon is used to specify devices on which paging and swapping are to take place. Calls to swapon normally occur in the system multi-user
initialization file /etc/rc making all swap devices available, so that the paging and swapping activity is interleaved across several
devices and files.
Normally, the first form is used:
-h Provide help
-V Display version
-s Display swap usage summary by device. Equivalent to "cat /proc/swaps". Not available before Linux 2.1.25.
-a All devices marked as ``swap'' swap devices in /etc/fstab are made available. Devices that are already running as swap are silently
skipped.
-e When -a is used with swapon, -e makes swapon silently skip devices that do not exist.
-p priority
Specify priority for swapon. This option is only available if swapon was compiled under and is used under a 1.3.2 or later kernel.
priority is a value between 0 and 32767. See swapon(2) for a full description of swap priorities. Add pri=value to the option field
of /etc/fstab for use with swapon -a.
Swapoff disables swapping on the specified devices and files. When the -a flag is given, swapping is disabled on all known swap devices
and files (as found in /proc/swaps or /etc/fstab).
NOTE
You should not use swapon on a file with holes. Swap over NFS may not work.
SEE ALSO
swapon(2), swapoff(2), fstab(5), init(8), mkswap(8), rc(8), mount(8)
FILES
/dev/hd?? standard paging devices
/dev/sd?? standard (SCSI) paging devices
/etc/fstab ascii filesystem description table
HISTORY
The swapon command appeared in 4.0BSD.
Linux 1.x 25 September 1995 SWAPON(8)