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drum(4) [ultrix man page]

drum(4) 						     Kernel Interfaces Manual							   drum(4)

Name
       drum - paging device

Description
       This  file refers to the paging device in use by the system.  This may actually be a subdevice of one of the disk drivers, but, in a system
       with paging interleaved across multiple disk drives, it provides an indirect driver for the multiple drives.

Restrictions
       Reads from the drum are not allowed across the interleaving boundaries.	Because these occur only every .5Mbytes or  so,  and  because  the
       system never allocates blocks across the boundary, this is usually not a problem.

Files
See Also
       MAKEDEV(8)

																	   drum(4)

Check Out this Related Man Page

VMSTAT(1)						      General Commands Manual							 VMSTAT(1)

NAME
vmstat - report virtual memory statistics SYNOPSIS
vmstat [ -fsi ] [ drives ] [ interval [ count ] ] DESCRIPTION
Vmstat delves into the system and normally reports certain statistics kept about process, virtual memory, disk, trap and cpu activity. If given a -f argument, it instead reports on the number of forks and vforks since system startup and the number of pages of virtual memory involved in each kind of fork. If given a -s argument, it instead prints the contents of the sum structure, giving the total number of several kinds of paging related events which have occurred since boot. If given a -i argument, it instead reports on the number of inter- rupts taken by each device since system startup. If none of these options are given, vmstat will report in the first line a summary of the virtual memory activity since the system has been booted. If interval is specified, then successive lines are summaries over the last interval seconds. ``vmstat 5'' will print what the system is doing every five seconds; this is a good choice of printing interval since this is how often some of the statistics are sampled in the system; others vary every second, running the output for a while will make it apparent which are recomputed every second. If a count is given, the statistics are repeated count times. The format fields are: Procs: information about numbers of processes in various states. r in run queue b blocked for resources (i/o, paging, etc.) w runnable or short sleeper (< 20 secs) but swapped Memory: information about the usage of virtual and real memory. Virtual pages are considered active if they belong to processes which are running or have run in the last 20 seconds. A ``page'' here is 1024 bytes. avm active virtual pages fre size of the free list Page: information about page faults and paging activity. These are averaged each five seconds, and given in units per second. re page reclaims (simulating reference bits) at pages attached (found in free list) pi pages paged in po pages paged out fr pages freed per second de anticipated short term memory shortfall sr pages scanned by clock algorithm, per-second up/hp/rk/ra: Disk operations per second (this field is system dependent). Typically paging will be split across several of the available drives. The number under each of these is the unit number. Faults: trap/interrupt rate averages per second over last 5 seconds. in (non clock) device interrupts per second sy system calls per second cs cpu context switch rate (switches/sec) Cpu: breakdown of percentage usage of CPU time us user time for normal and low priority processes sy system time id cpu idle If more than 4 disk drives are configured in the system, vmstat displays only the first 4 drives, with priority given to Massbus disk drives (i.e. if both Unibus and Massbus drives are present and the total number of drives exceeds 4, then some number of Unibus drives will not be displayed in favor of the Massbus drives). To force vmstat to display specific drives, their names may be supplied on the command line. FILES
/dev/kmem, /vmunix SEE ALSO
systat(1), iostat(1) The sections starting with ``Interpreting system activity'' in Installing and Operating 4.2bsd. 4th Berkeley Distribution March 15, 1986 VMSTAT(1)
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