Documentation/proc.txt update

[Jorge Nerin <comandante@zaralinux.com>]

Hello, this is a patch with some updates to the Documetation/proc.txt
file, basically it contains updates to the new files in /proc/<PID>, new
files in /proc, and a paragraph about /proc/sys/net/ipv4/tcp_ecn. It's
far from complete, but it's a start point.


--- old/proc.txt	Mon Oct 23 15:20:00 2000
+++ new/proc.txt	Mon Nov 13 00:20:24 2000
@@ -46,7 +46,7 @@
 the SuSE  Linux  distribution.  As  there is no complete documentation
for the
 /proc file  system and we've used many freely available sources to
write these
 chapters, it  seems  only  fair  to give the work back to the Linux
community.
-This work is based on the 2.2.* kernel version. I'm afraid it's still
far from
+This work is based on the 2.2.* kernel version and the upcomming 2.4.*.
I'm afraid it's still far from
 complete, but  we  hope  it will be useful. As far as we know, it is
the first
 'all-in-one' document  about the /proc file system. It is focused on
the Intel
 x86 hardware,  so if you are looking for PPC, ARM, SPARC, APX, etc.,
features,
@@ -92,7 +92,7 @@
 
 The proc  file  system acts as an interface to internal data structures
in the
 kernel. It  can  be  used to obtain information about the system and to
change
-certain kernel parameters at runtime.
+certain kernel parameters at runtime (sysctl).
 
 First, we'll  take  a  look  at the read-only parts of /proc. In
Chapter 2, we
 show you how you can use /proc/sys to change settings.
@@ -111,16 +111,17 @@

..............................................................................
  File    Content                                        
  cmdline Command line arguments                         
- environ Values of environment variables                
+ cpu	 Current and last cpu in wich it was executed		(2.4)(smp)
+ cwd	 Link to the Current Working Directory
+ environ Values of environment variables      
+ exe	 Link to the executable in the filesystem
  fd      Directory, which contains all file descriptors 
+ maps	 Maps to executables and library files			(2.4)
  mem     Memory held by this process                    
+ root	 Link to the root directory of  this process
  stat    Process status                                 
- status  Process status in human readable form          
- cwd     Link to the current working directory          
- exe     Link to the executable of this process         
- maps    Memory maps                                    
- root    Link to the root directory of this process     
  statm   Process memory status information              
+ status  Process status in human readable form          

..............................................................................
 
 For example, to get the status information of a process, all you have
to do is
@@ -131,6 +132,7 @@
   State:  R (running) 
   Pid:    5452 
   PPid:   743 
+  TracerPid:      0						(2.4)
   Uid:    501     501     501     501 
   Gid:    100     100     100     100 
   Groups: 100 14 16 
@@ -187,13 +189,20 @@
  devices     Available devices (block and character)           
  dma         Used DMS channels                                 
  filesystems Supported filesystems                             
+ driver	     Various drivers grouped here, currently rtc	(2.4)
+ execdomains Execdomains, related to security			(2.4)
+ fb	     Frame Buffer devices				(2.4)
+ fs	     File system parameters, currently nfs/exports	(2.4)
  ide         Directory containing info about the IDE subsystem 
  interrupts  Interrupt usage                                   
+ iomem	     Memory map						(2.4)
  ioports     I/O port usage                                    
- kcore       Kernel core image (can be ELF or A.OUT)           
+ irq	     Masks for irq to cpu affinity			(2.4)(smp?)
+ isapnp	     ISA PnP (Plug&Play) Info				(2.4)
+ kcore       Kernel core image (can be ELF or A.OUT(depreciated in
2.4))   
  kmsg        Kernel messages                                   
  ksyms       Kernel symbol table                               
- loadavg     Load average                                      
+ loadavg     Load average of last 1, 5 & 15 minutes                
  locks       Kernel locks                                      
  meminfo     Memory info                                       
  misc        Miscellaneous                                     
@@ -201,14 +210,19 @@
  mounts      Mounted filesystems                               
  net         Networking info (see text)                        
  partitions  Table of partitions known to the system           
+ pci	     Depreciated info of PCI bus (new way -> /proc/bus/pci/, 
+             decoupled by lspci					(2.4)
  rtc         Real time clock                                   
  scsi        SCSI info (see text)                              
  slabinfo    Slab pool info                                    
  stat        Overall statistics                                
  swaps       Swap space utilization                            
  sys         See chapter 2                                     
+ sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
+ tty	     Info of tty drivers
  uptime      System uptime                                     
  version     Kernel version                                    
+ video	     bttv info of video resources			(2.4)

..............................................................................
 
 You can,  for  example,  check  which interrupts are currently in use
and what
@@ -230,6 +244,68 @@
    15:          7          XT-PIC  ide1 
   NMI:          0 
 
+In 2.4.* a couple of lines where added to this file LOC & ERR (this
time is the
+output of a SMP machine):
+
+  > cat /proc/interrupts 
+
+             CPU0       CPU1       
+    0:    1243498    1214548    IO-APIC-edge  timer
+    1:       8949       8958    IO-APIC-edge  keyboard
+    2:          0          0          XT-PIC  cascade
+    5:      11286      10161    IO-APIC-edge  soundblaster
+    8:          1          0    IO-APIC-edge  rtc
+    9:      27422      27407    IO-APIC-edge  3c503
+   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
+   13:          0          0          XT-PIC  fpu
+   14:      22491      24012    IO-APIC-edge  ide0
+   15:       2183       2415    IO-APIC-edge  ide1
+   17:      30564      30414   IO-APIC-level  eth0
+   18:        177        164   IO-APIC-level  bttv
+  NMI:    2457961    2457959 
+  LOC:    2457882    2457881 
+  ERR:       2155
+
+NMI is incremented in this case because every timer interrupt generates
a NMI
+(Non Maskable Interrupt) which is used by the NMI Watchdog to detect
lookups.
+
+LOC is the local interrupt counter of the internal APIC of every CPU.
+
+ERR is incremented in the case of errors in the IO-APIC bus (the bus
that
+connects the CPUs in a SMP system. This means that an error has been
detected,
+the IO-APIC automatically retry the transmision, so it should not be a
big
+problem, but you should read the SMP-FAQ.
+
+In this context it could be interesting to note the new irq directory
in 2.4.
+It could be used to set IRQ to CPU affinity, this means that you can
"hook" an
+IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents
of the
+irq subdir is one subdir for each IRQ, and one file; prof_cpu_mask
+
+For example 
+  > ls /proc/irq/
+  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
+  1  11  13  15  17  19  3  5  7  9
+  > ls /proc/irq/0/
+  smp_affinity
+
+The contents of the prof_cpu_mask file and each smp_affinity file for
each IRQ
+is the same by default:
+
+  > cat /proc/irq/0/smp_affinity 
+  ffffffff
+
+It's a bitmask, in wich you can specify wich CPUs can handle the IRQ,
you can
+set it by doing:
+
+  > echo 1 > /proc/irq/prof_cpu_mask
+
+This means that only the first CPU will handle the IRQ, but you can
also echo 5
+wich means that only the first and fourth CPU can handle the IRQ.
+
+The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
+between all the CPUs which are allowed to handle it. As usual the
kernel has
+more info than you and does a better job than you, so the defaults are
the
+best choice for almost everyone.
 
 There are  three  more  important subdirectories in /proc: net, scsi,
and sys.
 The general  rule  is  that  the  contents,  or  even  the  existence
of these
@@ -1306,6 +1382,15 @@
 
 TCP settings
 ------------
+
+tcp_ecn
+-------
+
+This file controls the use of the ECN bit in the IPv4 headers, this is
a new
+feature about Explicit Congestion Notification, but some routers and
firewalls
+block trafic that has this bit set, so it could be necessary to echo 0
to
+/proc/sys/net/ipv4/tcp_ecn, if you want to talk to this sites. For more
info
+you could read RFC2481.
 
 tcp_retrans_collapse
 --------------------

-- 
Jorge Nerin
<comandante@zaralinux.com>
-
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