readme.top

linux下获取一些环境信息的代码

Credit for this belongs to:
Jim / James C. Warner, <[e-mail]>

----------------------------------

Ok, ok, I yield -- most of what follows has been removed from the manual page
and packaged separately as this README (hey, it was only TEMPORARY insanity).

Of course, that means that now absolutely nobody will ever read it.

This is probably a good thing...


## Table of Contents ---------------------------------------------------##
      # the only darn thing that wasn't in the man page
   CUSTOMIZING the Sources
      # the following carry their original topic numbers
   DIFFERENCES / New Features
      Interface Etiquette
      Expanded Configurable Display Support
      Enhanced Field/Column Management
      Customization Flexibility
   NOTES and Rantings
      The top Binary
      Comparing Performance
      Cost of Stuff
      The top Sources
   EXAMPLES of Windows
      The 'A' Mode Command Toggle
      STACKIN' & WHACKIN' Windows
      ALL TOGETHER Now, Window(s)


## CUSTOMIZING the Sources ---------------------------------------------##

Listed below are the conditionals available should you wish to recompile
this top.  The author's favorite is:  PRETEND4CPUS.

That's the #define allowing you to simulate an SMP environment, and
(perhaps) impress your friends.  It's currently set to display four
separate CPUs, but could easily be changed.

   Caution: do NOT use this provision in an effort to impress someone
            who truly possesses such a machine!  The fact that all 4
            CPUs show the same dynamic results will likely have the
            opposite effect.


//#define ATEOJ_REPORT            /* report a bunch of stuff, at end-of-job  */
//#define CASEUP_HEXES            /* show any hex values in upper case       */
//#define CASEUP_SCALE            /* show scaled time/num suffix upper case  */
//#define CASEUP_SUMMK            /* show memory summary kilobytes with 'K'  */
//#define POSIX_CMDLIN            /* use '[ ]' for kernel threads, not '( )' */
//#define PRETEND2_5_X            /* pretend we're linux 2.5.x (for IO-wait) */
//#define PRETEND4CPUS            /* pretend we're smp with 4 ticsers (sic)  */
//#define PRETENDNOCAP            /* use a terminal without essential caps   */
//#define SORT_SUPRESS            /* *attempt* to reduce qsort overhead      */
//#define STDOUT_IOLBF            /* disable our own stdout _IOFBF override  */
//#define USE_LIB_STA3            /* use lib status (3 ch) vs. proc_t (1 ch) */
//#define WARN_NOT_SMP            /* restrict '1' & 'I' commands to true smp */


## 6. DIFFERENCES / New Features ---------------------------------------##
       The  following  summarizes  differences  between this top and your
       former top.  It was originally based  on  procps-2.0.7.   However,
       except  for  the separate/summary CPU toggle, all of these differ-
       ences also apply through procps-2.0.10.

   6a. Interface Etiquette
       -*-  Input and  output  are  far  more  carefully  implemented  in
            this top.   You won't be subjected to 4 - 5 'Unknown command'
            messages should you press the wrong key.

       -*-  You need suffer a confirmation message only when the  results
            of a command are not obvious by their effects on the display.

       -*-  The Help screen will no longer overflow,  even  when  running
            with a 24 row xterm (vt100).

       -*-  The  fields  selection/ordering  screens  do  not  carelessly
            destroy important information through unintended line  wraps.

       -*-  Should  you  narrow  a  xterm  window to less than 80 columns
            while this top is running, you  will  not  be  left  with  an
            utterly worthless, embarrassing display.

   6b. Expanded Configurable Display Support
       -*-  In  an SMP environment, you can choose between a summary dis-
            play or you may show each cpu  separately.   No  longer  must
            this choice be irrevocably made at startup.

       -*-  There  are  new  fields  and  with  this top,  any  field  is
            selectable for sorting.  Plus,  your  sorted  column  can  be
            instantly reversed with just a single keystroke.

       -*-  You  may optionally apply 2 distinct types of highlighting to
            running tasks and/or sorted columns.  With  this top,  you'll
            be  able  to instantly spot running tasks and always know the
            current sort field.

       -*-  While you could  continue  to  use  the  more  familiar  (and
            boring)  monochrome display, you might want to try this top's
            new color display.  You can even create your own unique  col-
            ors  used in summaries, messages, headings and tasks, each of
            which can be made persistent until you choose to change them.

       -*-  Up  to four separate windows can be displayed simultaneously,
            giving you four separate ways to sort and view the tasks cur-
            rently cluttering up your system.  You could have one view by
            pids, another by cpu usage, yet another showing  memory  con-
            sumption.  You get the idea...

       -*-  Each window comes with pre-configured (but user configurable)
            fields and you can size each window individually.

       -*-  Virtually every one of this top's options (summaries, fields,
            colors,  sorted  column, etc.) is separately configurable for
            each of those four windows.

            Heck, you can even change a window's name, if you don't  care
            for  top's  choices.  Your changes will be reflected not only
            when you're in what top calls alternate-display mode but also
            on his special new 'Windows' help screen.

       -*-  And,  [ ** Drum-Roll + Ta-Da ** ] with just one keystroke you
            can quickly switch between full-screen  and  multiple  window
            modes!   Or, with a different keystroke, toggle a single win-
            dow Off for now, then On again later!!

   6c. Enhanced Field/Column Management
       -*-  Many Field/Column names have been changed to make  them  more
            intuitive,  more  self-descriptive.   And  with  this top you
            won't be fooled with field choices that are "not  yet  imple-
            mented".

       -*-  Task memory statistics are more meaningful and more accurate.

       -*-  You'll finally have complete display integrity regardless  of
            field  selections,  their  order  or  screen width.  And that
            means the command column no longer need be kept as the right-
            most  field,  lest  your  screen turn to <bleep> when all the
            following columns get misaligned.

   6d. Customization Flexibility
       -*-  You have complete program naming  freedom  with  no  internal
            ties  to  a  specific  personal configuration file.  Symbolic
            links could be  used  to  establish  different  configuration
            files  reflecting  the  different  personalities of your cus-
            tomized "tops", under whatever aliases you've used.

            Thus, you could have an  alias  for  running  top  in  'Batch
            mode',  another  for when you work from the Linux console and
            maybe a third used with X-Windows.  All of  that,  yet  still
            just a single binary image!

       -*-  All  of your configuration choices can be preserved in a per-
            sonal configuration file, including any  changes  made  on  a
            per-window  basis.   Thus,  once  you personalize things they
            remain personalized until you decide to  change  them  again.
            This top has been completely cured of:
                     i-cant-remember-so-please-do-that-all-over-again
                                         ( and again, and again ... )

            The  bottom  line  is  this:  if  you save your configuration
            before quitting top, upon restart  the  display  will  appear
            exactly as you left it.  And that means you no longer have to
            keep top  running  until-the-end-of-time  (ok,  a  long  time
            anyway), lest your customizations go bye-bye.


## 7. NOTES and Rantings -----------------------------------------------##
   7a. The top Binary
       To  whom  it may (should) concern:  this top, even with its vastly
       expanded capabilities, is only slightly larger than the  old  top.
       Were it not for extensive help text and additional sort callbacks,
       it would be smaller.
                       Throw source carelessly at objectives, it will
                       produce equally careless machine instructions.
                       example: (num_pages - an_address)/1024 == duh?
                       kicker: document result as broken, due to elf!
                       ----------------------------------------------
                       I know you're out there, are you getting this?

       Now, as for all those new capabilities like colors and windows and
       highlighting, you'd expect this top to be the "mother of all pigs"
       compared to old top  --  right?

       Yea, with this top expect following piglets:
        . A smaller virtual image and resident footprint
        . Slightly fewer major page faults
        . A large reduction in minor page faults for SMP
        . The same or better response time
        . The same or even less CPU costs

       Ideally any comparison of the old and new top  should  be  against
       the  same libproc format (32-bit or 64-bit tics) and run in a true
       or simulated SMP environment (producing separate CPU stats).  This
       latter  requirement  will  coax  old  top  into  handling  his own
       '/proc/stat' access  --  something this top always does, but  with
       less cost.

   7b. Comparing Performance
       Even  with equivalent libraries and '/proc/stat' access, it's dif-
       ficult to  accurately  compare  tops  using  their  own  displays.
       Results  for  these  cpu-intensive programs (who frequently exceed
       their time-slice) generally show a wide disparity in  %CPU.   This
       is due to differing call patterns, kernel preemptions and the tim-
       ing of process snapshots.  For slightly better results, start each
       program with the following commands:
            ./old-top -d 0.5
            nice -n-10 ./new-top -d 0.4

       While actually putting this top at a performance disadvantage, the
       higher scheduling priority and staggered timing will  periodically
       yield  a  somewhat  truer  picture.   You could even reverse those
       roles and get similar results.

       The most consistent performance results  will  be  obtained  'off-
       line',  using  your  shell's time pipe or the time program itself.
       And even in a single processor environment or  without  equivalent
       libraries,  total cpu costs (user time + system time) are similar.

       However, this top's cpu costs ARE influenced by  the  capabilities
       you  choose to exploit, even if they don't SEEM to be reflected in
       such timings.  So let's examine some...

   7c. Cost of Stuff
       Colors Cost  --  Nada (almost).
          Once the terminfo strings are built (at  and  during  a  user's
          behest)  they  are  SAVED  with each window's stuff.  And while
          there will be extra tty escape sequences transmitted because of
          colors, it makes no difference which 'char *' is actually used.

       Highlighting Cost  --  Nada (maybe), or blame it on Rio.
          On second thought, let's blame it on the user.

          For row highlighting, there is only the cost of those extra tty
          escape  sequences  (same as for colors).  For column highlight-
          ing, there is a fairly significant cost associated with  column
          transition  management  combined  with  even  more  tty output.
          These increased costs are incurred on every task display row.

          Sooo... hey USER  --  do NOT highlight COLUMNS.  You  shouldn't
          need  a  constant  visual  reminder  of your chosen sort field.
          However, if you forget which field top is sorting it can  serve
          as a quick visual reminder.

       Windows Cost  --  Nada (if just 1 window).
          If more than 1 window, almost certainly NOT Nada so blame it on
          reality.  Colors are not an issue, but those sort fields are.

          If we could trust the user to always select the same 'c' state,
          'S' state and sort field (hey, why ya got multiple windows then
          user, huh?) AND if we can trust someone to recompile top with a
          #define enabled, then we could achieve 'Nada'.

          Ok,  not likely, so we're gonna' be doing multiple sorts.  BUT,
          it may not be as bad as it sounds.  Those sorts involve  point-
          ers only.  And, that's as good as it gets !  (right Mr. N?)

   7d. The top Sources
       top.h
          Unlike  his predecessor, this top has a proper header file.  It
          contains ONLY declarations, NOT  definitions.   And  there  are
          several  conditionals  present  to help with further customiza-
          tions and experimentation.  All are Off by default.

       top.c
          Hopefully proves that source code needn't  be  a  disorganized,
          misaligned  MESS.   And,  WHO  says  a source listing shouldn't
          occasionally make you SMILE?  Why, top.c even does a darn  good
          job  of  following the suggestions in a document hardly anybody
          seems to observe.