Messages in this thread | | | Date | Wed, 26 May 2004 12:10:01 +0200 | From | Matthias Schniedermeyer <> | Subject | Re: why swap at all? |
| |
On Wed, May 26, 2004 at 07:48:10PM +1000, Nick Piggin wrote: > John Bradford wrote: > >Quote from Nick Piggin <nickpiggin@yahoo.com.au>: > > > >>Even for systems that don't *need* the extra memory space, swap can > >>actually provide performance improvements by allowing unused memory > >>to be replaced with often-used memory. > > > > > >That's true, but it's not a magical property of swap space - extra physical > >RAM would do more or less the same thing. > > > > Well it is a magical property of swap space, because extra RAM > doesn't allow you to replace unused memory with often used memory. > > The theory holds true no matter how much RAM you have. Swap can > improve performance. It can be trivially demonstrated.
The other way around can be "demonstrated" equally trivially.
In my personal machine i have 3GB of RAM and i regularly create DVD-ISO-Images (about 2 per day). After creating an image (reading up to 4,4GB and writing up to 4,4GB) the cache is 100% trashed(1). With swap it would be even more trashed then it is without swap(1).
1: This has "always(tm)" been so since i began burning DVDs 3 years ago. Beginning from kernel 2.4.4-2.4.25 and 2.6.4-2.6.6. Currently i use 2.6.5. (This is no typo!)
I have only tested the "with swap"-case with 2.4.4 as i didn't use swap after 2.4.4 trashed so badly with swap enabled. But i don't think that things have changed so fundamentaly that the "with swap"-case is better(FOR ME!) than the "without swap"-case.
Bis denn
-- Real Programmers consider "what you see is what you get" to be just as bad a concept in Text Editors as it is in women. No, the Real Programmer wants a "you asked for it, you got it" text editor -- complicated, cryptic, powerful, unforgiving, dangerous.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |