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一份很好的linux入门资料

is,&nbsp;if&nbsp;you&nbsp;have&nbsp;anything&nbsp;that&nbsp;runs&nbsp;really&nbsp;heavy&nbsp;disk&nbsp;I/O&nbsp;like&nbsp;web&nbsp;<BR>
page&nbsp;logging&nbsp;put&nbsp;it&nbsp;on&nbsp;the&nbsp;fastest&nbsp;drive&nbsp;you've&nbsp;got.&nbsp;If&nbsp;you&nbsp;have&nbsp;<BR>
a&nbsp;RAID&nbsp;drive&nbsp;and&nbsp;a&nbsp;normal&nbsp;drive&nbsp;make&nbsp;sure&nbsp;that&nbsp;all&nbsp;your&nbsp;log&nbsp;<BR>
activities&nbsp;write&nbsp;to&nbsp;the&nbsp;RAID&nbsp;disk.&nbsp;&nbsp;<BR>
&nbsp;<BR>
/&nbsp;contains&nbsp;most&nbsp;of&nbsp;the&nbsp;system&nbsp;utilities&nbsp;and&nbsp;doesn't&nbsp;get&nbsp;used&nbsp;<BR>
much.&nbsp;These&nbsp;can&nbsp;be&nbsp;shipped&nbsp;off&nbsp;to&nbsp;the&nbsp;slowest&nbsp;disk.&nbsp;&nbsp;<BR>
&nbsp;<BR>
/var/log&nbsp;contains&nbsp;a&nbsp;_lot_&nbsp;of&nbsp;logging&nbsp;information.&nbsp;Best&nbsp;on&nbsp;a&nbsp;fast&nbsp;<BR>
disk&nbsp;&nbsp;<BR>
&nbsp;<BR>
/usr&nbsp;is&nbsp;typically&nbsp;on&nbsp;a&nbsp;separate&nbsp;partition&nbsp;anyway.&nbsp;Place&nbsp;it&nbsp;<BR>
wherever,&nbsp;but&nbsp;if&nbsp;you&nbsp;have&nbsp;a&nbsp;lot&nbsp;of&nbsp;clients&nbsp;starting&nbsp;lots&nbsp;of&nbsp;X&nbsp;<BR>
applications,&nbsp;some&nbsp;speedy&nbsp;disk&nbsp;may&nbsp;be&nbsp;in&nbsp;order.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Before&nbsp;deciding&nbsp;on&nbsp;your&nbsp;partitioning&nbsp;scheme,&nbsp;you&nbsp;really&nbsp;need&nbsp;to&nbsp;<BR>
know&nbsp;exactly&nbsp;what&nbsp;sort&nbsp;of&nbsp;applications&nbsp;you&nbsp;will&nbsp;be&nbsp;running.&nbsp;Here&nbsp;<BR>
are&nbsp;two&nbsp;typical&nbsp;examples&nbsp;of&nbsp;the&nbsp;sorts&nbsp;of&nbsp;configurations&nbsp;that&nbsp;you&nbsp;<BR>
need&nbsp;to&nbsp;know&nbsp;about:&nbsp;&nbsp;<BR>
&nbsp;<BR>
Mail:&nbsp;Sendmail&nbsp;writes&nbsp;to&nbsp;two&nbsp;main&nbsp;locations&nbsp;mail&nbsp;queue&nbsp;(usually&nbsp;<BR>
/var/spool/mqueue&nbsp;and&nbsp;/var/spool/mail&nbsp;as&nbsp;well&nbsp;as&nbsp;possibly&nbsp;having&nbsp;<BR>
to&nbsp;read&nbsp;into&nbsp;a&nbsp;user's&nbsp;home&nbsp;directory&nbsp;for&nbsp;a&nbsp;procmail&nbsp;configuration&nbsp;<BR>
OR&nbsp;.forward&nbsp;file.&nbsp;If&nbsp;you&nbsp;are&nbsp;attempting&nbsp;to&nbsp;boost&nbsp;sendmail&nbsp;<BR>
performance&nbsp;and&nbsp;nfs&nbsp;mounted&nbsp;mail&nbsp;queue,&nbsp;mail&nbsp;spool,&nbsp;or&nbsp;home&nbsp;<BR>
directories&nbsp;might&nbsp;cause&nbsp;some&nbsp;serious&nbsp;issues&nbsp;and&nbsp;you'll&nbsp;have&nbsp;to&nbsp;<BR>
take&nbsp;a&nbsp;look&nbsp;into&nbsp;your&nbsp;mail&nbsp;scheme.&nbsp;For&nbsp;more&nbsp;information,&nbsp;you&nbsp;<BR>
should&nbsp;look&nbsp;at&nbsp;the&nbsp;section&nbsp;on&nbsp;mail&nbsp;server&nbsp;tuning.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Apache&nbsp;uses&nbsp;several&nbsp;different&nbsp;files,&nbsp;two&nbsp;logs&nbsp;files&nbsp;for&nbsp;logging&nbsp;<BR>
and&nbsp;access&nbsp;to&nbsp;the&nbsp;actual&nbsp;pages.&nbsp;While&nbsp;you&nbsp;may&nbsp;think&nbsp;that&nbsp;you&nbsp;want&nbsp;<BR>
your&nbsp;web&nbsp;pages&nbsp;on&nbsp;the&nbsp;fastest&nbsp;drive,&nbsp;apache&nbsp;spends&nbsp;quite&nbsp;a&nbsp;bit&nbsp;of&nbsp;<BR>
time&nbsp;writing&nbsp;to&nbsp;logs&nbsp;files.&nbsp;You&nbsp;will&nbsp;want&nbsp;to&nbsp;make&nbsp;sure&nbsp;that&nbsp;you&nbsp;<BR>
take&nbsp;this&nbsp;into&nbsp;consideration&nbsp;in&nbsp;developing&nbsp;a&nbsp;partition&nbsp;scheme.&nbsp;&nbsp;<BR>
&nbsp;<BR>
2.5&nbsp;Swap&nbsp;Space&nbsp;<BR>
&nbsp;<BR>
Swap&nbsp;partitions.&nbsp;How&nbsp;often&nbsp;do&nbsp;we&nbsp;see&nbsp;someone&nbsp;screwing&nbsp;up&nbsp;a&nbsp;<BR>
perfectly&nbsp;good&nbsp;system&nbsp;by&nbsp;a&nbsp;badly&nbsp;configured&nbsp;swap&nbsp;space?&nbsp;The&nbsp;<BR>
difference&nbsp;can&nbsp;be&nbsp;phenomenal.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Always&nbsp;have&nbsp;swap&nbsp;space&nbsp;on&nbsp;a&nbsp;separate&nbsp;partition(s).&nbsp;The&nbsp;use&nbsp;of&nbsp;<BR>
swap&nbsp;files&nbsp;can&nbsp;really&nbsp;grind&nbsp;a&nbsp;system&nbsp;to&nbsp;a&nbsp;halt&nbsp;under&nbsp;even&nbsp;<BR>
moderate&nbsp;load.&nbsp;When&nbsp;using&nbsp;a&nbsp;swap&nbsp;file,&nbsp;it&nbsp;adds&nbsp;an&nbsp;extra&nbsp;layer&nbsp;of&nbsp;<BR>
system&nbsp;calls&nbsp;for&nbsp;every&nbsp;write&nbsp;and&nbsp;read.&nbsp;Instead&nbsp;of&nbsp;talking&nbsp;to&nbsp;<BR>
&quot;raw&quot;&nbsp;disk,&nbsp;you&nbsp;are&nbsp;writing&nbsp;into&nbsp;the&nbsp;filesystem.&nbsp;Access&nbsp;to&nbsp;the&nbsp;<BR>
raw&nbsp;filesystem&nbsp;will&nbsp;be&nbsp;quicker&nbsp;&nbsp;<BR>
&nbsp;<BR>
Two&nbsp;smaller&nbsp;swaps&nbsp;on&nbsp;two&nbsp;disks&nbsp;is&nbsp;better&nbsp;than&nbsp;one&nbsp;big&nbsp;one&nbsp;on&nbsp;a&nbsp;<BR>
single&nbsp;disk.&nbsp;Based&nbsp;on&nbsp;the&nbsp;same&nbsp;reasons&nbsp;as&nbsp;earlier,&nbsp;there&nbsp;is&nbsp;also&nbsp;<BR>
an&nbsp;advantage&nbsp;to&nbsp;using&nbsp;RAID&nbsp;for&nbsp;your&nbsp;swap&nbsp;partition&nbsp;as&nbsp;well.&nbsp;&nbsp;<BR>
&nbsp;<BR>
If&nbsp;possible,&nbsp;make&nbsp;the&nbsp;swap&nbsp;partition&nbsp;the&nbsp;first&nbsp;partition&nbsp;on&nbsp;the&nbsp;<BR>
disk&nbsp;(it&nbsp;is&nbsp;physically&nbsp;located&nbsp;closest&nbsp;to&nbsp;the&nbsp;outer&nbsp;edge&nbsp;of&nbsp;the&nbsp;<BR>
hard&nbsp;drive&nbsp;platter).&nbsp;There&nbsp;can&nbsp;be&nbsp;up&nbsp;to&nbsp;a&nbsp;factor&nbsp;of&nbsp;2&nbsp;difference&nbsp;<BR>
in&nbsp;transfer&nbsp;rates&nbsp;for&nbsp;data&nbsp;out&nbsp;on&nbsp;the&nbsp;edge&nbsp;compared&nbsp;to&nbsp;the&nbsp;middle&nbsp;<BR>
of&nbsp;the&nbsp;disk.&nbsp;As&nbsp;the&nbsp;kernel&nbsp;uses&nbsp;swap&nbsp;space&nbsp;as&nbsp;extra&nbsp;memory,&nbsp;the&nbsp;<BR>
quicker&nbsp;you&nbsp;can&nbsp;get&nbsp;this&nbsp;stuff&nbsp;on&nbsp;and&nbsp;off&nbsp;disk,&nbsp;the&nbsp;better&nbsp;your&nbsp;<BR>
performance.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Have&nbsp;at&nbsp;least&nbsp;twice&nbsp;the&nbsp;amount&nbsp;of&nbsp;physical&nbsp;RAM&nbsp;set&nbsp;aside&nbsp;as&nbsp;swap&nbsp;<BR>
space.&nbsp;&nbsp;<BR>
&nbsp;<BR>
2.6&nbsp;Further&nbsp;information&nbsp;<BR>
&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;From&nbsp;the&nbsp;Configuration&nbsp;HOWTO:&nbsp;General&nbsp;System&nbsp;Setup&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://metalab.unc.edu/LDP/HOWTO/Config-HOWTO-2.html#ss2.4">http://metalab.unc.edu/LDP/HOWTO/Config-HOWTO-2.html#ss2.4</A>&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Multi&nbsp;Disk&nbsp;System&nbsp;Tuning&nbsp;HOWTO&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://metalab.unc.edu/LDP/HOWTO/Multi-Disk-HOWTO.html">http://metalab.unc.edu/LDP/HOWTO/Multi-Disk-HOWTO.html</A>&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Large&nbsp;Disk&nbsp;HOWTO&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://metalab.unc.edu/LDP/HOWTO/mini/Large-Disk.html">http://metalab.unc.edu/LDP/HOWTO/mini/Large-Disk.html</A>&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Software-RAID&nbsp;HOWTO&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://metalab.unc.edu/LDP/HOWTO/mini/Software-RAID.html">http://metalab.unc.edu/LDP/HOWTO/mini/Software-RAID.html</A>&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ultra-DMA&nbsp;Mini&nbsp;HOWTO&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<A HREF="http://metalab.unc.edu/LDP/HOWTO/mini/Ultra-DMA.html">http://metalab.unc.edu/LDP/HOWTO/mini/Ultra-DMA.html</A>&nbsp;&nbsp;<BR>
&nbsp;<BR>
3.&nbsp;Networking&nbsp;<BR>
&nbsp;<BR>
TBD&nbsp;&nbsp;<BR>
&nbsp;<BR>
3.1&nbsp;Further&nbsp;information&nbsp;<BR>
&nbsp;<BR>
4.&nbsp;Memory&nbsp;<BR>
&nbsp;<BR>
The&nbsp;final&nbsp;piece&nbsp;of&nbsp;the&nbsp;basic&nbsp;tuning&nbsp;is&nbsp;to&nbsp;look&nbsp;at&nbsp;the&nbsp;use&nbsp;of&nbsp;<BR>
memory&nbsp;in&nbsp;your&nbsp;machine.&nbsp;This&nbsp;is&nbsp;not&nbsp;just&nbsp;the&nbsp;main&nbsp;memory&nbsp;(RAM),&nbsp;<BR>
but&nbsp;the&nbsp;use&nbsp;of&nbsp;caches&nbsp;and&nbsp;access&nbsp;between&nbsp;the&nbsp;various&nbsp;levels&nbsp;of&nbsp;<BR>
memory.&nbsp;&nbsp;<BR>
&nbsp;<BR>
4.1&nbsp;Unix&nbsp;Memory&nbsp;<BR>
&nbsp;<BR>
In&nbsp;order&nbsp;to&nbsp;understand&nbsp;how&nbsp;memory&nbsp;can&nbsp;be&nbsp;optimised,&nbsp;you&nbsp;need&nbsp;to&nbsp;<BR>
know&nbsp;a&nbsp;little&nbsp;about&nbsp;how&nbsp;the&nbsp;underlying&nbsp;operating&nbsp;system&nbsp;allocates&nbsp;<BR>
memory&nbsp;to&nbsp;applications.&nbsp;Since&nbsp;Linux&nbsp;is&nbsp;a&nbsp;form&nbsp;of&nbsp;Unix,&nbsp;it&nbsp;follows&nbsp;<BR>
many&nbsp;of&nbsp;the&nbsp;same&nbsp;basic&nbsp;principles,&nbsp;so&nbsp;well&nbsp;talk&nbsp;about&nbsp;general&nbsp;<BR>
unix&nbsp;models&nbsp;here.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Unix&nbsp;uses&nbsp;an&nbsp;&quot;Always&nbsp;Full&quot;&nbsp;model&nbsp;for&nbsp;memory.&nbsp;All&nbsp;memory&nbsp;is&nbsp;always&nbsp;<BR>
being&nbsp;used,&nbsp;as&nbsp;in,&nbsp;it&nbsp;always&nbsp;contains&nbsp;some&nbsp;form&nbsp;of&nbsp;data.&nbsp;<BR>
Typically&nbsp;this&nbsp;is&nbsp;used&nbsp;to&nbsp;buffer&nbsp;information&nbsp;from&nbsp;slower&nbsp;forms&nbsp;of&nbsp;<BR>
memory&nbsp;like&nbsp;hard&nbsp;disks&nbsp;etc.&nbsp;Whether&nbsp;or&nbsp;not&nbsp;that&nbsp;information&nbsp;is&nbsp;<BR>
relevant&nbsp;is&nbsp;inconsequential.&nbsp;&nbsp;<BR>
&nbsp;<BR>
The&nbsp;first&nbsp;thing&nbsp;a&nbsp;unix&nbsp;box&nbsp;does&nbsp;when&nbsp;it&nbsp;starts&nbsp;up&nbsp;is&nbsp;grab&nbsp;all&nbsp;the&nbsp;<BR>
memory&nbsp;and&nbsp;divide&nbsp;it&nbsp;into&nbsp;a&nbsp;number&nbsp;of&nbsp;chunks.&nbsp;Typically&nbsp;this&nbsp;<BR>
consists&nbsp;of:&nbsp;&nbsp;<BR>
&nbsp;<BR>
Kernel&nbsp;Space&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A&nbsp;memory&nbsp;space&nbsp;that&nbsp;is&nbsp;reserved&nbsp;exclusively&nbsp;for&nbsp;the&nbsp;kernel&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;to&nbsp;use&nbsp;and&nbsp;abuse.&nbsp;This&nbsp;is&nbsp;the&nbsp;minimal&nbsp;breathing&nbsp;area&nbsp;needed&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for&nbsp;the&nbsp;kernel&nbsp;to&nbsp;run&nbsp;scheduling,&nbsp;keep&nbsp;itself&nbsp;permanently&nbsp;in&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;memory&nbsp;and&nbsp;other&nbsp;really&nbsp;important&nbsp;stuff&nbsp;like&nbsp;device&nbsp;drivers&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;etc.&nbsp;&nbsp;<BR>
User&nbsp;Space&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The&nbsp;memory&nbsp;space&nbsp;used&nbsp;to&nbsp;keep&nbsp;application&nbsp;level&nbsp;code.&nbsp;This&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;is&nbsp;all&nbsp;applications&nbsp;-&nbsp;even&nbsp;server&nbsp;processes&nbsp;like&nbsp;web/mail&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;servers,&nbsp;a&nbsp;user&nbsp;login&nbsp;shell&nbsp;or&nbsp;X&nbsp;Windows.&nbsp;Inside&nbsp;the&nbsp;user&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;space,&nbsp;each&nbsp;application&nbsp;(process)&nbsp;has&nbsp;its&nbsp;own&nbsp;block&nbsp;of&nbsp;space&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;to&nbsp;operate.&nbsp;No&nbsp;other&nbsp;application&nbsp;is&nbsp;allowed&nbsp;to&nbsp;invade&nbsp;this&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;space.&nbsp;If&nbsp;it&nbsp;does,&nbsp;the&nbsp;typical&nbsp;result&nbsp;is&nbsp;a&nbsp;core&nbsp;dump.&nbsp;(There&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;are&nbsp;caveats&nbsp;to&nbsp;this&nbsp;for&nbsp;things&nbsp;like&nbsp;Shared&nbsp;Memory&nbsp;usage&nbsp;that&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;puts&nbsp;in&nbsp;an&nbsp;explicit&nbsp;common&nbsp;space.)&nbsp;&nbsp;<BR>
Buffer&nbsp;Space&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This&nbsp;is&nbsp;basically&nbsp;everything&nbsp;else&nbsp;of&nbsp;the&nbsp;memory&nbsp;that&nbsp;is&nbsp;not&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;taken&nbsp;up&nbsp;by&nbsp;the&nbsp;requirements&nbsp;of&nbsp;user&nbsp;and&nbsp;kernel&nbsp;space.&nbsp;This&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;is&nbsp;used&nbsp;to&nbsp;buffer&nbsp;I/O&nbsp;for&nbsp;disks,&nbsp;network&nbsp;cards&nbsp;etc.&nbsp;Also,&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;importantly,&nbsp;this&nbsp;is&nbsp;used&nbsp;for&nbsp;DMA&nbsp;transfers&nbsp;between&nbsp;devices&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;to&nbsp;make&nbsp;things&nbsp;much&nbsp;quicker.&nbsp;Buffering&nbsp;is&nbsp;applied&nbsp;to&nbsp;both&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;read&nbsp;and&nbsp;write&nbsp;operations.&nbsp;Attempt&nbsp;to&nbsp;write&nbsp;something&nbsp;to&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;disk,&nbsp;and&nbsp;it&nbsp;will&nbsp;be&nbsp;first&nbsp;written&nbsp;to&nbsp;memory&nbsp;and&nbsp;then&nbsp;at&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;some&nbsp;later&nbsp;time&nbsp;it&nbsp;will&nbsp;be&nbsp;written&nbsp;to&nbsp;the&nbsp;physical&nbsp;media&nbsp;as&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;well.&nbsp;&nbsp;<BR>
&nbsp;<BR>
The&nbsp;job&nbsp;of&nbsp;the&nbsp;kernel&nbsp;is&nbsp;to&nbsp;manage&nbsp;all&nbsp;of&nbsp;these&nbsp;different&nbsp;spaces&nbsp;<BR>
according&nbsp;to&nbsp;the&nbsp;requirements&nbsp;of&nbsp;the&nbsp;currently&nbsp;running&nbsp;processes.&nbsp;<BR>
When&nbsp;you&nbsp;attempt&nbsp;to&nbsp;start&nbsp;a&nbsp;new&nbsp;application,&nbsp;it&nbsp;must&nbsp;first&nbsp;find&nbsp;<BR>
some&nbsp;memory&nbsp;to&nbsp;use&nbsp;that&nbsp;is&nbsp;big&nbsp;enough,&nbsp;allocate&nbsp;it&nbsp;and&nbsp;then&nbsp;start&nbsp;<BR>
your&nbsp;application.&nbsp;If&nbsp;there&nbsp;is&nbsp;not&nbsp;enough&nbsp;physical&nbsp;RAM,&nbsp;it&nbsp;must&nbsp;<BR>
make&nbsp;some&nbsp;by&nbsp;swapping&nbsp;out&nbsp;onto&nbsp;disk&nbsp;another&nbsp;application,&nbsp;or&nbsp;maybe&nbsp;<BR>
raid&nbsp;buffer&nbsp;space,&nbsp;and&nbsp;then&nbsp;copy&nbsp;your&nbsp;application&nbsp;into&nbsp;memory&nbsp;<BR>
before&nbsp;beginning&nbsp;the&nbsp;execution.&nbsp;Some&nbsp;of&nbsp;this&nbsp;task&nbsp;involves&nbsp;<BR>
&nbsp;re-arranging&nbsp;memory&nbsp;to&nbsp;get&nbsp;a&nbsp;contiguous&nbsp;chunk&nbsp;of&nbsp;space&nbsp;large&nbsp;<BR>
enough.&nbsp;(Coincidently,&nbsp;these&nbsp;are&nbsp;also&nbsp;why&nbsp;applications&nbsp;on&nbsp;Unix&nbsp;<BR>
machines&nbsp;tend&nbsp;to&nbsp;appear&nbsp;to&nbsp;typically&nbsp;take&nbsp;longer&nbsp;to&nbsp;start&nbsp;than&nbsp;<BR>
the&nbsp;equivalent&nbsp;Win32&nbsp;or&nbsp;MacOS&nbsp;app).&nbsp;&nbsp;<BR>
&nbsp;<BR>
＞<I>From&nbsp;this&nbsp;you&nbsp;should&nbsp;be&nbsp;starting&nbsp;to&nbsp;see&nbsp;some&nbsp;of&nbsp;the&nbsp;problems&nbsp;</I><BR>
that&nbsp;could&nbsp;occur&nbsp;that&nbsp;make&nbsp;your&nbsp;machine&nbsp;run&nbsp;slowly.&nbsp;Too&nbsp;little&nbsp;<BR>
RAM&nbsp;and&nbsp;the&nbsp;kernel&nbsp;spends&nbsp;its&nbsp;time&nbsp;swapping&nbsp;(commonly&nbsp;known&nbsp;as&nbsp;<BR>
Thrashing&nbsp;when&nbsp;it&nbsp;gets&nbsp;bad).&nbsp;Badly&nbsp;setup&nbsp;swap&nbsp;space&nbsp;and&nbsp;it&nbsp;slows&nbsp;<BR>
down&nbsp;that&nbsp;operation.&nbsp;Too&nbsp;many&nbsp;apps&nbsp;running&nbsp;and&nbsp;the&nbsp;kernel&nbsp;spends&nbsp;<BR>
all&nbsp;its&nbsp;time&nbsp;searching&nbsp;for&nbsp;new&nbsp;space&nbsp;or&nbsp;re-arranging&nbsp;memory&nbsp;to&nbsp;<BR>
fit.&nbsp;&nbsp;<BR>
&nbsp;<BR>
4.2&nbsp;Memory&nbsp;Types&nbsp;<BR>
&nbsp;<BR>
Over&nbsp;the&nbsp;years,&nbsp;the&nbsp;typical&nbsp;PC&nbsp;memory&nbsp;chip&nbsp;has&nbsp;gone&nbsp;through&nbsp;a&nbsp;<BR>
whole&nbsp;swathe&nbsp;of&nbsp;acronyms.&nbsp;Lets&nbsp;look&nbsp;at&nbsp;a&nbsp;few&nbsp;of&nbsp;them:&nbsp;&nbsp;<BR>
&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DRAM:&nbsp;Dynamic&nbsp;RAM.&nbsp;The&nbsp;original&nbsp;memory&nbsp;type.&nbsp;Could&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;allow&nbsp;one&nbsp;operation&nbsp;at&nbsp;once:&nbsp;read&nbsp;or&nbsp;write.&nbsp;&nbsp;<BR>
&nbsp;<BR>