proc.txt

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        Adaptec SCSI BIOS: Enabled 
                      IRQ: 10 
                     SCBs: Active 0, Max Active 2, 
                           Allocated 15, HW 16, Page 255 
               Interrupts: 160328 
        BIOS Control Word: 0x18b6 
     Adapter Control Word: 0x005b 
     Extended Translation: Enabled 
  Disconnect Enable Flags: 0xffff 
       Ultra Enable Flags: 0x0001 
   Tag Queue Enable Flags: 0x0000 
  Ordered Queue Tag Flags: 0x0000 
  Default Tag Queue Depth: 8 
      Tagged Queue By Device array for aic7xxx host instance 0: 
        {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
      Actual queue depth per device for aic7xxx host instance 0: 
        {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
  Statistics: 
  (scsi0:0:0:0) 
    Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
    Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
    Total transfers 160151 (74577 reads and 85574 writes) 
  (scsi0:0:6:0) 
    Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
    Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
    Total transfers 0 (0 reads and 0 writes) 


1.6 Parallel port info in /proc/parport
---------------------------------------

The directory  /proc/parport  contains information about the parallel ports of
your system.  It  has  one  subdirectory  for  each port, named after the port
number (0,1,2,...).

These directories contain the four files shown in Table 1-8.


Table 1-8: Files in /proc/parport 
..............................................................................
 File      Content                                                             
 autoprobe Any IEEE-1284 device ID information that has been acquired.         
 devices   list of the device drivers using that port. A + will appear by the
           name of the device currently using the port (it might not appear
           against any). 
 hardware  Parallel port's base address, IRQ line and DMA channel.             
 irq       IRQ that parport is using for that port. This is in a separate
           file to allow you to alter it by writing a new value in (IRQ
           number or none). 
..............................................................................

1.7 TTY info in /proc/tty
-------------------------

Information about  the  available  and actually used tty's can be found in the
directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
this directory, as shown in Table 1-9.


Table 1-9: Files in /proc/tty 
..............................................................................
 File          Content                                        
 drivers       list of drivers and their usage                
 ldiscs        registered line disciplines                    
 driver/serial usage statistic and status of single tty lines 
..............................................................................

To see  which  tty's  are  currently in use, you can simply look into the file
/proc/tty/drivers:

  > cat /proc/tty/drivers 
  pty_slave            /dev/pts      136   0-255 pty:slave 
  pty_master           /dev/ptm      128   0-255 pty:master 
  pty_slave            /dev/ttyp       3   0-255 pty:slave 
  pty_master           /dev/pty        2   0-255 pty:master 
  serial               /dev/cua        5   64-67 serial:callout 
  serial               /dev/ttyS       4   64-67 serial 
  /dev/tty0            /dev/tty0       4       0 system:vtmaster 
  /dev/ptmx            /dev/ptmx       5       2 system 
  /dev/console         /dev/console    5       1 system:console 
  /dev/tty             /dev/tty        5       0 system:/dev/tty 
  unknown              /dev/tty        4    1-63 console 


1.8 Miscellaneous kernel statistics in /proc/stat
-------------------------------------------------

Various pieces   of  information about  kernel activity  are  available in the
/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
since the system first booted.  For a quick look, simply cat the file:

  > cat /proc/stat
  cpu  2255 34 2290 22625563 6290 127 456
  cpu0 1132 34 1441 11311718 3675 127 438
  cpu1 1123 0 849 11313845 2614 0 18
  intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
  ctxt 1990473
  btime 1062191376
  processes 2915
  procs_running 1
  procs_blocked 0

The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
lines.  These numbers identify the amount of time the CPU has spent performing
different kinds of work.  Time units are in USER_HZ (typically hundredths of a
second).  The meanings of the columns are as follows, from left to right:

- user: normal processes executing in user mode
- nice: niced processes executing in user mode
- system: processes executing in kernel mode
- idle: twiddling thumbs
- iowait: waiting for I/O to complete
- irq: servicing interrupts
- softirq: servicing softirqs

The "intr" line gives counts of interrupts  serviced since boot time, for each
of the  possible system interrupts.   The first  column  is the  total of  all
interrupts serviced; each  subsequent column is the  total for that particular
interrupt.

The "ctxt" line gives the total number of context switches across all CPUs.

The "btime" line gives  the time at which the  system booted, in seconds since
the Unix epoch.

The "processes" line gives the number  of processes and threads created, which
includes (but  is not limited  to) those  created by  calls to the  fork() and
clone() system calls.

The  "procs_running" line gives the  number of processes  currently running on
CPUs.

The   "procs_blocked" line gives  the  number of  processes currently blocked,
waiting for I/O to complete.


------------------------------------------------------------------------------
Summary
------------------------------------------------------------------------------
The /proc file system serves information about the running system. It not only
allows access to process data but also allows you to request the kernel status
by reading files in the hierarchy.

The directory  structure  of /proc reflects the types of information and makes
it easy, if not obvious, where to look for specific data.
------------------------------------------------------------------------------

------------------------------------------------------------------------------
CHAPTER 2: MODIFYING SYSTEM PARAMETERS
------------------------------------------------------------------------------

------------------------------------------------------------------------------
In This Chapter
------------------------------------------------------------------------------
* Modifying kernel parameters by writing into files found in /proc/sys
* Exploring the files which modify certain parameters
* Review of the /proc/sys file tree
------------------------------------------------------------------------------


A very  interesting part of /proc is the directory /proc/sys. This is not only
a source  of  information,  it also allows you to change parameters within the
kernel. Be  very  careful  when attempting this. You can optimize your system,
but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
production system.  Set  up  a  development machine and test to make sure that
everything works  the  way  you want it to. You may have no alternative but to
reboot the machine once an error has been made.

To change  a  value,  simply  echo  the new value into the file. An example is
given below  in the section on the file system data. You need to be root to do
this. You  can  create  your  own  boot script to perform this every time your
system boots.

The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
general things  in  the operation of the Linux kernel. Since some of the files
can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
documentation and  source  before actually making adjustments. In any case, be
very careful  when  writing  to  any  of these files. The entries in /proc may
change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
review the kernel documentation in the directory /usr/src/linux/Documentation.
This chapter  is  heavily  based  on the documentation included in the pre 2.2
kernels, and became part of it in version 2.2.1 of the Linux kernel.

2.1 /proc/sys/fs - File system data
-----------------------------------

This subdirectory  contains  specific  file system, file handle, inode, dentry
and quota information.

Currently, these files are in /proc/sys/fs:

dentry-state
------------

Status of  the  directory  cache.  Since  directory  entries  are  dynamically
allocated and  deallocated,  this  file indicates the current status. It holds
six values, in which the last two are not used and are always zero. The others
are listed in table 2-1.


Table 2-1: Status files of the directory cache 
..............................................................................
 File       Content                                                            
 nr_dentry  Almost always zero                                                 
 nr_unused  Number of unused cache entries                                     
 age_limit  
            in seconds after the entry may be reclaimed, when memory is short 
 want_pages internally                                                         
..............................................................................

dquot-nr and dquot-max
----------------------

The file dquot-max shows the maximum number of cached disk quota entries.

The file  dquot-nr  shows  the  number of allocated disk quota entries and the
number of free disk quota entries.

If the number of available cached disk quotas is very low and you have a large
number of simultaneous system users, you might want to raise the limit.

file-nr and file-max
--------------------

The kernel  allocates file handles dynamically, but doesn't free them again at
this time.

The value  in  file-max  denotes  the  maximum number of file handles that the
Linux kernel will allocate. When you get a lot of error messages about running
out of  file handles, you might want to raise this limit. The default value is
10% of  RAM in kilobytes.  To  change it, just  write the new number  into the
file:

  # cat /proc/sys/fs/file-max 
  4096 
  # echo 8192 > /proc/sys/fs/file-max 
  # cat /proc/sys/fs/file-max 
  8192 


This method  of  revision  is  useful  for  all customizable parameters of the
kernel - simply echo the new value to the corresponding file.

Historically, the three values in file-nr denoted the number of allocated file
handles,  the number of  allocated but  unused file  handles, and  the maximum
number of file handles. Linux 2.6 always  reports 0 as the number of free file
handles -- this  is not an error,  it just means that the  number of allocated
file handles exactly matches the number of used file handles.

Attempts to  allocate more  file descriptors than  file-max are  reported with
printk, look for "VFS: file-max limit <number> reached".

inode-state and inode-nr
------------------------

The file inode-nr contains the first two items from inode-state, so we'll skip
to that file...

inode-state contains  two  actual numbers and five dummy values. The numbers
are nr_inodes and nr_free_inodes (in order of appearance).

nr_inodes
~~~~~~~~~

Denotes the  number  of  inodes the system has allocated. This number will
grow and shrink dynamically.

nr_free_inodes
--------------

Represents the  number of free inodes. Ie. The number of inuse inodes is
(nr_inodes - nr_free_inodes).

super-nr and super-max
----------------------

Again, super  block structures are allocated by the kernel, but not freed. The
file super-max  contains  the  maximum  number  of super block handlers, where
super-nr shows the number of currently allocated ones.

Every mounted file system needs a super block, so if you plan to mount lots of
file systems, you may want to increase these numbers.

aio-nr and aio-max-nr
---------------------

aio-nr is the running total of the number of events specified on the
io_setup system call for all currently active aio contexts.  If aio-nr
reaches aio-max-nr then io_setup will fail with EAGAIN.  Note that
raising aio-max-nr does not result in the pre-allocation or re-sizing
of any kernel data structures.

2.2 /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
-----------------------------------------------------------

Besides these  files, there is the subdirectory /proc/sys/fs/binfmt_misc. This
handles the kernel support for miscellaneous binary formats.

Binfmt_misc provides  the ability to register additional binary formats to the
Kernel without  compiling  an additional module/kernel. Therefore, binfmt_misc
needs to  know magic numbers at the beginning or the filename extension of the
binary.

It works by maintaining a linked list of structs that contain a description of
a binary  format,  including  a  magic  with size (or the filename extension),
offset and  mask,  and  the  interpreter name. On request it invokes the given
interpreter with  the  original  program  as  argument,  as  binfmt_java  and
binfmt_em86 and  binfmt_mz  do.  Since binfmt_misc does not define any default
binary-formats, you have to register an additional binary-format.

There are two general files in binfmt_misc and one file per registered format.
The two general files are register and status.