2002-10-14 03:27:07 +05:30
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Ok, ok, I yield -- much of what follows has been removed from the manual page
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and packaged separately as this README. Which means, of course, that absolutely
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nobody will ever read it.
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If that proves to be wrong, I hope the individual will drop a line to:
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procps-feedback@lists.sourceforge.net
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Just say "Ha, I read it!" and the author will die happy (but not right away).
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Thanks.
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## Table of Contents ---------------------------------------------------##
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NOTES and Rantings
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CUSTOMIZING the Sources
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## 7. NOTES and Rantings -----------------------------------------------##
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7a. The top Binary
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To whom it may (should) concern: this top, even with its vastly
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expanded capabilities, is only slightly larger than the old top.
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Were it not for extensive help text and additional sort callbacks,
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it would be smaller.
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Throw source carelessly at objectives, it will
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produce equally careless machine instructions.
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example: (num_pages - an_address)/1024 == duh?
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kicker: document result as broken, due to elf!
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----------------------------------------------
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I know you're out there, are you getting this?
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Now, as for all those new capabilities like colors and windows and
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highlighting, you'd expect this top to be the "mother of all pigs"
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compared to old top -- right?
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Yea, with this top expect following piglets:
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. A smaller virtual image and resident footprint
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. Slightly fewer major page faults
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. A large reduction in minor page faults for SMP
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. The same or better response time
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. The same or even less CPU costs
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Ideally any comparison of the old and new top should be against
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the same libproc format (32-bit or 64-bit tics) and run in a true
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or simulated SMP environment (producing separate CPU stats). This
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latter requirement will coax old top into handling his own
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'/proc/stat' access -- something this top always does, but with
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less cost.
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7b. Comparing Performance
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Even with equivalent libraries and '/proc/stat' access, it's dif-
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ficult to accurately compare tops using their own displays.
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Results for these cpu-intensive programs (who frequently exceed
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their time-slice) generally show a wide disparity in %CPU. This
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is due to differing call patterns, kernel preemptions and the tim-
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ing of process snapshots. For slightly better results, start each
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program with the following commands:
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./old-top -d 0.5
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nice -n-10 ./new-top -d 0.4
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While actually putting this top at a performance disadvantage, the
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higher scheduling priority and staggered timing will periodically
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yield a somewhat truer picture. You could even reverse those
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roles and get similar results.
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The most consistent performance results will be obtained 'off-
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line', using your shell's time pipe or the time program itself.
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And even in a single processor environment or without equivalent
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libraries, total cpu costs (user time + system time) are similar.
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However, this top's cpu costs ARE influenced by the capabilities
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you choose to exploit, even if they don't SEEM to be reflected in
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such timings. So let's examine some...
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7c. Cost of Stuff
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Colors Cost -- Nada (almost).
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Once the terminfo strings are built (at and during a user's
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behest) they are SAVED with each window's stuff. And while
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there will be extra tty escape sequences transmitted because of
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colors, it makes no difference which 'char *' is actually used.
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Highlighting Cost -- Nada (maybe), or blame it on Rio.
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On second thought, let's blame it on the user.
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For row highlighting, there is only the cost of those extra tty
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escape sequences (same as for colors). For column highlight-
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ing, there is a fairly significant cost associated with column
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transition management combined with even more tty output.
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These increased costs are incurred on every task display row.
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Sooo... hey USER -- do NOT highlight COLUMNS. You shouldn't
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need a constant visual reminder of your chosen sort field.
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However, if you forget which field top is sorting it can serve
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as a quick visual reminder.
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Windows Cost -- Nada (if just 1 window).
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If more than 1 window, almost certainly NOT Nada so blame it on
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reality. Colors are not an issue, but those sort fields are.
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If we could trust the user to always select the same 'c' state,
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'S' state and sort field (hey, why ya got multiple windows then
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user, huh?) AND if we can trust someone to recompile top with a
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#define enabled, then we could achieve 'Nada'.
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Ok, not likely, so we're gonna' be doing multiple sorts. BUT,
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it may not be as bad as it sounds. Those sorts involve point-
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ers only. And, that's as good as it gets ! (right Mr. N?)
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7d. The top Sources
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top.h
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Unlike his predecessor, this top has a proper header file. It
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contains ONLY declarations, NOT definitions. And there are
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several conditionals present to help with further customiza-
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tions and experimentation. All are Off by default.
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top.c
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Hopefully proves that source code needn't be a disorganized,
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misaligned MESS. And, WHO says a source listing shouldn't
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occasionally make you SMILE? Why, top.c even does a darn good
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job of following the suggestions in a document hardly anybody
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seems to observe.
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the Linus Torvalds CodingStyle guidelines ...
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-*- -*- -*- on indentation + etc. -*- -*- -*-
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well almost all, except for those stinkin'...
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I suppose even Linus Torvalds is entitled to err now and again.
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How so you say? Tabs, me' bucko, stinkin' tabs! That, plus the
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simplistic position regarding indentation espoused in that other-
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wise excellent document.
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-*- Rant On, and on -*-
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Let's compare two approaches to the tab/indentation issue with a
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small code sample using tabs then spaces. This snippet happens to
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be the key to top's use of dynamic colors on many static screens,
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while also ensuring screen width isn't exceeded so as to avoid
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line wraps. We'll view just the first 40 columns, assuming one
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wishes to occasionally provide comments to the right of actual
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code (you do, don't you?).
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Then YOU decide which approach makes the most SENSE!
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Stinkin' Tabs versus Spaces: the Linus way
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Hey, where'd my +----+----1----+----2----+----3----+----4+
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many code lines | while (*sub_beg) { :
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up-and-gone-to? | switch (*sub_end:
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| case 0: :
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Gosh, wonder if | \ Tabs Induced / :
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Linus expects a | case 1: :
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fellow to stick | + WASTE-Lands! + case 5: :
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his comments on | :
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the left side?! | + Not a Living + :
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Ever see source | + line-of-code + :
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with not enough | :
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whitespace; and | / To Be Found! \ :
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this is better? | default::
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| :
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Oh lookie here, \ } :
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there's just a hint of REAL code! ----> if (0 >= room) b:
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/ } /* end: while 'subtrin:
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+----------------------------------------+
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Spaces versus Stinkin' Tabs: the other way
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+----+----1----+----2----+----3----+----4+
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Wow, now this is | while (*sub_beg) { :
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Visible hackin'! | switch (*sub_end) { :
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| case 0: :
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Hmmm, wonder how | *(sub_end + 1) = '\0'; :
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many programmers | case 1: case 2: case 3: case:
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read those lines | case 5: case 6: case 7: case:
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from the LEFT to | cap = Curwin->captab[(int:
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the RIGHT? This | *sub_end = '\0'; :
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"innovation" may | PUTP("%s%.*s%s", cap, roo:
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possibly benefit | room -= (sub_end - sub_be:
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those particular | sub_beg = ++sub_end; :
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kinds of people, | break; :
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you agree? Duh! | default: :
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| ++sub_end; :
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AND, there might | } :
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even be room for | if (0 >= room) break; :
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unseen comments! | } /* end: while 'subtrings' */ :
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+----------------------------------------+
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Gosh, I just don't KNOW -- it's such a TOUGH choice...
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Oh you Stinkin' Tabs: correspondence, Who-Cares; documentation,
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Oh-Alright; even scripts, Well-If-You-Must. But you have NO place
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within the code-space of MY C-source listing! So be gone
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already!!
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In Summation...
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- If you want to use tabs to the right of the code, go-for-it.
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But PLEASE, not ever in the C-source code-space, thank-you-
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kindly. Just use three little ol' spaces (exactly 3, no-more,
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no-less) where you WOULD have stuck a stinkin' tab.
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We'll get far more READABLE files, much less WAISTED precious
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horizontal space, more consistent CURSORS and on, and ON, AND
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ON! Plus, without those awful *the-devil's-own-handiwork*, the
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aforementioned document need NEVER speak of their EVILS again.
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- Lastly, since SPACES (not stinkin' tabs) are SO beneficial,
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maybe we should use just a few more of 'em. Some of those C-
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thingies are VERY sensitive -- they don't like being TOUCHED
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by any other syntax element! Which ones? Why these guys:
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braces, reserved words and binary operators
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( it's the TRUTH, they told me themselves )
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It's so EASY to keep 'em HAPPY! And lo-and-behold, the combi-
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nation of <sp>thingy<sp> turns out to be a darn effective bug
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repellent, too. So much so, one can actually code while
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TOTALLY NUDE yet still avoid them ol' bug-bytes (sic-sic)!
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step
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down_from
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me_punctilious
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soap-box_once_again
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[1 +5 +5 +5 = huh?]
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## CUSTOMIZING the Sources ---------------------------------------------##
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Listed below are the conditionals available should you wish to recompile
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this top. The author's favorite is: PRETEND4CPUS.
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That's the #define allowing you to simulate an SMP environment, and
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(perhaps) impress your friends. It's currently set to display four
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separate CPUs, but could easily be changed.
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Caution: do NOT use this provision in an effort to impress someone
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who truly possesses such a machine! The fact that all 4
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CPUs show the same dynamic results will likely have the
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opposite effect.
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Enjoy...
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//#define ATEOJ_REPORT /* report a bunch of stuff, at end-of-job */
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//#define CASEUP_HEXES /* show any hex values in upper case */
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//#define CASEUP_SCALE /* show scaled time/num suffix upper case */
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//#define CASEUP_SUMMK /* show memory summary kilobytes with 'K' */
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//#define POSIX_CMDLIN /* use '[ ]' for kernel threads, not '( )' */
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//#define PRETEND2_5_X /* pretend we're linux 2.5.x (for IO-wait) */
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//#define PRETEND4CPUS /* pretend we're smp with 4 ticsers (sic) */
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//#define PRETENDNOCAP /* use a terminal without essential caps */
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//#define SORT_SUPRESS /* *attempt* to reduce qsort overhead */
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//#define USE_LIB_STA3 /* use lib status (3 ch) vs. proc_t (1 ch) */
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//#define YIELDCPU_OFF /* hang on tight, DON'T issue sched_yield */
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//#define WARN_NOT_SMP /* restrict '1' & 'I' commands to true smp */
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