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Ramdisks - Now We Are Talking Hyperspace

linux-mag.com

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Re: Ramdisks - Now We Are Talking Hyperspace

#2
For several months I have a 500MB tmpfs ramdisk (which I will probably turn into a ramfs one after reading that article).

I put my browser cache, several logging files and other volatile things there. Whenever I download something just to dispose it later, it goes in there. If I try something stupid with a lot files or some big ones, it goes in there.

It feels much nicer than to fragment the harddisk for such things; maybe it is just a placebo but it makes me happy. And of course access and usage of those files is blazing fast.

PS: Having Opera's temporary download directory automatically wiped away alone is worth it... :)

Re: Ramdisks - Now We Are Talking Hyperspace

#3
On Acard's page that CD-ROM sized module supporting up to 64GB without memory included costs $550. The memory for it would cost about $900 more. Maybe Joel could get this for all employees after they get tired of their new X25s.

Re: Ramdisks - Now We Are Talking Hyperspace

#5
post #2

For several months I have a 500MB tmpfs ramdisk (which I will probably turn into a ramfs one after reading that article). I put my browser cache, several logging files and other volatile things there. Whenever I download something just to dispose it later, it goes in there. If I try something stupid with a lot files or some big ones, it goes in there. It feels much nicer than to fragment the harddisk for such things;…

[deleted]

Re: Ramdisks - Now We Are Talking Hyperspace

#6
Can I ask a question?

Does anyone know how to signal to the Operating System NOT TO CACHE these filesystems? This would be ram caching a ram cache which wouldn't make performance sense.

I cannot work out if that is part of the tmpfs/ramdisk driver itself, or if people who write these sort of articles don't know about normal read/write caching that occurs in all operating systems.

Re: Ramdisks - Now We Are Talking Hyperspace

#7
A thing you can do with these is use an "at boot time, prime the ramfs" technique on file/web servers to pin important static files in memory if your normal serving patterns will push certain things in and out of the page cache more than you like.

Re: Ramdisks - Now We Are Talking Hyperspace

#8
post #6

Can I ask a question? Does anyone know how to signal to the Operating System NOT TO CACHE these filesystems? This would be ram caching a ram cache which wouldn't make performance sense. I cannot work out if that is part of the tmpfs/ramdisk driver itself, or if people who write these sort of articles don't know about normal read/write caching that occurs in all operating systems.

Both ramfs and tmpfs on Linux cause writes directly to the page cache, just like a normal write but without a backing store (though in tmpfs' case, the backing store is swap). So there is no double RAM usage.

This is confirmed in these docs:

Documentation/filesystems/ramfs-rootfs-initramfs.txt

Documentation/filesystems/tmpfs.txt

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