Messages in this thread | | | Date | Tue, 12 Jul 2005 17:53:32 -0400 | From | Wakko Warner <> | Subject | Re: Swap partition vs swap file |
| |
Helge Hafting wrote: > Wakko Warner wrote: > You don't need to zero out swapfiles. You can fill them with anything, > even /dev/urandom. Zero-filling may be faster though. A swapfile > is not zero the second time you use it - then it contains leftovers > from last time.
I understand this part.
> >So are you saying that if I create a swap partition it's best to use dd to > >zero it out before mkswap? If no, then why would a file be different? I > >know there's no documented way to create a file of given size without > >writing content. I saw windows grow a pagefile several meg in less than a > >second so I'm sure that it doesn't zero out the space first. > > Linux doesn't grow swapfiles at all. It uses what's there at mkswap time. > You can make new ones of course - manually.
And this part. I've never known linux to grow the swap file. I did try the sparse one a long time ago. Of course it didn't work.
> >As far as portable, we're talking about linux, portability is not an issue > >in this case. I myself don't use swap files (or partitions), however, > >there > >was a project I recall that would dynamically add/remove swap as needed. > >Creating a file of 20-50mb quickly would have been beneficial. > > You can create 50M quickly - even if it actually have to be written. If > you can't, don't use that device for swap.
Not all systems can create 50mb in a short time. Especially when the system/device is under load. Not all systems have multiple disks either.
> Ability to allocate some blocks without actually writing to them is nice > for this > purpose, but current linux filesystems doesn't have an api for doing that. > The necessary changes would touch all existing writeable filesystems, and > that is a lot of work for very little gain. As they say, you don't > create swapfiles > all that often. The time saved on swapfile creation might take a long > time to > make up for the time spent on making, auditing and supporting those > changes.
I hadn't considered this "portability" so I didn't understand at that point.
-- Lab tests show that use of micro$oft causes cancer in lab animals - 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/
| |