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    SubjectDocumentation/proc.txt update
    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
    -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.,
    @@ -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
    -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
    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
    +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
    +connects the CPUs in a SMP system. This means that an error has been
    +the IO-APIC automatically retry the transmision, so it should not be a
    +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
    +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
    +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
    +block trafic that has this bit set, so it could be necessary to echo 0
    +/proc/sys/net/ipv4/tcp_ecn, if you want to talk to this sites. For more
    +you could read RFC2481.

    Jorge Nerin
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