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Thread: Linux Kernel Power Management Targeting Memory

  1. #11
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    There are pci-e ramdrives, and there's no need for RAID - even a single stick of DDR3 is faster than SATA-3.

  2. #12
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    Quote Originally Posted by curaga View Post
    There are pci-e ramdrives, and there's no need for RAID - even a single stick of DDR3 is faster than SATA-3.
    Have a link? And if you want a ram drive that isn't going to lose its data as soon as you power off then it doesn't matter how fast it is. What I'm thinking of is using a computer as a dedicated RAM drive, so if you could create a SATA connection then you can boot from it. Sure it won't be as fast as being directly on the board or on a PCIe bus but it'd be very "portable" and still faster than any other SSD.

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  4. #14
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    Quote Originally Posted by Luke_Wolf View Post
    But.... RAMDrive....
    Tmpfs is better than ramfs

  5. #15
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    Quote Originally Posted by Thaodan View Post
    Tmpfs is better than ramfs
    That depends on your purpose, but generally speaking tmpfs is safer to use and makes more sense as a RAM drive. It'd be nice if there was a way to prevent tmpfs from accessing swap, but I personally never use swap so I guess I don't have much to worry about.

  6. #16
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    Quote Originally Posted by schmidtbag View Post
    That depends on your purpose, but generally speaking tmpfs is safer to use and makes more sense as a RAM drive. It'd be nice if there was a way to prevent tmpfs from accessing swap, but I personally never use swap so I guess I don't have much to worry about.
    The explanation I've heard is that tmpfs is just the disk cache, presented as a filesystem.
    Of course, caching in swap is rather pointless, though perhaps not entirely.

  7. #17
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    Quote Originally Posted by Ibidem View Post
    The explanation I've heard is that tmpfs is just the disk cache, presented as a filesystem.
    Of course, caching in swap is rather pointless, though perhaps not entirely.
    I'm not sure about that.... you can mount a tmpfs to any location you want and of any size you want. It is a RAM filesystem, it just doesn't dynamically expand like ramfs. I'm not sure of any simple way to directly access disk cache - it sounds like a severe security flaw to me.

  8. #18
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    Quote Originally Posted by schmidtbag View Post
    I'm not sure about that.... you can mount a tmpfs to any location you want and of any size you want. It is a RAM filesystem, it just doesn't dynamically expand like ramfs. I'm not sure of any simple way to directly access disk cache - it sounds like a severe security flaw to me.
    1: Sorry for the unclear wording: it is not the cache of another filesystem, but a "filesystem" backed only by RAM used by the disk caching code, as if you had a cache for another filesystem, but no file or device to back that:
    Quote Originally Posted by Documentation/fs/tmpfs.txt
    tmpfs puts everything into the kernel internal caches and grows and
    shrinks to accommodate the files it contains and is able to swap
    unneeded pages out to swap space. It has maximum size limits which can
    be adjusted on the fly via 'mount -o remount ...'
    2: It does dynamically expand, as written above. But it has limits. And that and whether it can swap are the main difference from ramfs. (ramfs does not swap.)

    (If you want a _good_ explanation, refer to the document within the kernel source tree having the name mentioned...)
    Last edited by Ibidem; 04-13-2013 at 10:23 PM.

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