Re: [gentoo-user] Swap performance

[Alan McKinnon <alan.mckinnon@gmail.com>]

Apparently, though unproven, at 18:58 on Wednesday 25 May 2011, Volker Armin 
Hemmann did opine thusly:

> On Wednesday 25 May 2011 10:31:19 Paul Hartman wrote:
> > When I move the swap to a slow SD card instead (2MB/sec transfer
> > rate), even in that slow device, swapoff on the eMMC swap partition
> > with ~500M in-use takes about 2 or 3 minutes at most with the data
> > being swapped slowly into the SD card.
> > 
> > So I think in your case it should be much faster than that!
> 
> you are comparing apples with oranges (harddisks with moving arms with
> solid state devices).
> 
> Do yourself a favour. Look up how long a harddisk needs to position its
> head.
> 
> Now you can calculate how many times a second a harddisk can position its
> head.
> 
> Now remember: swap is stupid, so lots and lots of head movement needed (and
> a cash flush is running too - so even more movements to write all that
> crap to disk),
> 
> The result: the whole mess is fscking slow.
> 
> You can have a nice fat raid with nice and fast harddisks - if you try to
> stream to a 15 year old DLT drive with 5/10mb/sec speed the dlt drive will
> constantly rewind - because harddisks suck when they have to seek. And swap
> (just like a backup) = lots and lots and lots of seeks.

That reminds me of how SSDs ought to be much faster than hard disks.

But every time I use my Acer netbook (8G SSD) I curse and swear and commit 
random acts of violence - that first gen SSD controller is the worst possible 
thing to ever hit computers. I swear the 4G SDHC expansion card is leaps 
faster....

(completely OT, I know. I'll keep quiet now.)

-- 
alan dot mckinnon at gmail dot com