Unstable kernel,ginete afto???

[Christos Ricudis]

Hello I.Ioannou!

  On 28 Aug 01, I.Ioannou wrote to All with subject "Re: Unstable kernel,
ginete afto???":

 >>  roryt at roryt.gr->Tin ksereis thn mala#%$^kia pou ekane o Linus
 >> me ton VM pou apaitei na exeis roryt at roryt.gr->swap toulaxiston 
 >> diplasia ths ram sou ? 
 >> Nai to kserw alla emena den me "epeireazei"? dioti exw 256 RAM
 >> kai 128 swap.

 I> Se gelasane, me 2.4.x theleis swap >= 2 X RAM

1) Disk space is CHEAP, me ta shmerina mege8h diskwn mporeis na exei aneta swap
2x, 3x, 4x to RAM size sou. 

1.5) RAM SIZE IS CHEAP - balte PERISSOTERH MNHMH kai LIGOTERO SWAP SPACE. 

2) Ola eksartwntai apo to workload. O genikos kanonas einai oti ena systhma den
prepei na aggizei to swap space (opote de se noiazei poso swap space exeis :>).
Apo ekei kai pera yparxoyn orismena workloads gia ta opoia to 2.4 katanalwnei
poly perissotero swap page apo to 2.2

3) Na 8ymaste oti mono to RSS ("data+stack") ginetai swap out, oxi to full
memory space toy process (to text segment ("executable code") brisketai etsi ki
alliws sto disko, den yparxei anagkh na to kaneis swap out). 

4) Oi kanones toy styl "swap space = 2x RAM size" einai aplws rules of thumb.
Ti kanei to mhxanhma, gia ti douleia proorizetai? An einai p.x. server, to
performance toy apo to shmeio poy 8a arxisei na kanei swap kai meta 8a einai
aisxro, diplasiaste th mnhmh toy. An einai to proswpiko sas workstation,
xesthkame gia to performance sas, balte osh ligh mnhmh 8elete :>. 

5) Einai sxedon axrhsto na kaneis reclaim used swap space. Aplws to
xrhsimopoieis san ena cyclic buffer. To swap space megalwnei mexri na ftasei ta
max virtual memory requirements toy mhxanhmatos, kai paramenei ekei. Deite to
peirama poy ekana me peiramatozwa Indikous Mozilles Ergasthriou : 

* Katw apo to synh8ismeno workload toy mhxanhmatos moy (exw 512mb RAM) to swap
space einai 0.

* Arxizw n'anoigw Mozilles. 

* Gyrw ston dwdekato Mozilla, arxizei na ayksanetai to swap space usage. 

* Otan exw ftasei stoys dekaennia Mozilles, to swap space moy einai sta 50MB.

* Proxwraw se ekka8aristikes epixeirhseis, kai ystera apo mia genoktonia
Mozillwn, to swap space usage moy paramenei sta 50MB

* Ksananoigw toys Mozilles kai parathrw oti to swap space paramenei sta8ero sta
50MB, mexri na ftasw pali toys dekaennia Mozilles, ystera arxizei pali na
ayksanetai.  

6) Ean exeis ftasei sto shmeio na GEMISEIS to swap space sou, to systhma sou
exei plhsiasei toso poly to shmeio ths apolyths axrhstias, poy ligh diafora 8a
kanei na prospa8hseis na epanakthseis unused swap space - etsi ki alliws se
ligo 8a sou teleiwsei h mnhmh kai ta processes 8'arxisoyn na peftoun san
pagwmenes myges mia xeimwniatikh nyxta pagetwna ths sibhrias epanw sta
kalogyalismena plakakia toy dapedou kanontas "plok plok". 

7) To pio xrhsimo rule of thumb apo osa aforoun to swap space, einai : NEVER,
NEVER SWAP. Kai kalytero performence 8a exete, kai ligoteres anousies
syzhthseis gia ton pollaplasiasth toy mege8ous ths RAM poy mas dinei to swap
space 8a exoume. 

--
Christos Ricudis

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