Messages in this thread |  | | | Date | Wed, 26 May 2004 20:33:28 +1000 | | From | Nick Piggin <> | | Subject | Re: why swap at all? |
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Matthias Schniedermeyer wrote: > 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). >
I don't disagree that you could find a situation where swap is worse than no swap. I don't understand what you mean by trashed and more trashed though :)
Creating your ISOs makes your system swap a lot when swap is enabled?
> > > > 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. >
The 2.6 VM has changed pretty fundamentally. It would be good if you could retest. - 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/
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