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    SubjectRe: Proposal: make RAID6 code optional
    On Sat, 18 Apr 2009, Prakash Punnoor wrote:

    > On Samstag 18 April 2009 10:09:54 Michael Tokarev wrote:
    > > Prakash Punnoor wrote:
    > > > Hi,
    > > >
    > > > as I am using only RAID5 I wonder why the RAID6 code also needs to be
    > > > built. Here is a rough patch of making RAID6 optional (but depending on
    > > > raid456) without reording of functions to minimize ifdef scattering.
    > > > (I also haven't checked yet who needs ASYNC_MEMCPY and ASYNC_XOR...)
    > > > It would probably be nicer to make RAID4/5 and RAID6 independently
    > > > selectable of each other. But that requires more refactoring, as I can
    > > > see.
    > >
    > > Hm. In "old good days" there were 3 independent kernel modules,
    > > named raid4, raid5 and raid6. Later on, they got merged into one
    > > since they share quite alot of the code, and has only a few specific
    > > parts. Now you're trying to separate them back somewhat....
    > >
    > > What's your goal? What's the problem you're trying to solve?
    > Having duplicate code is not good, of course. But unused code is also not
    > good. As I said, I only use RAID5, so I don't need RAID6 support. The RAID6
    > support enlarges kernel (the built-in.o in drivers/md grows from 325kb to
    > 414kb in my case), making boot time and compile time longer

    By a few ms perhaps - nothing that you'd ever notice in real life... A
    small price to pay for the shared code. If you were to split them all
    again, the combined total size would be greater still.

    > - admittedly not
    > by a big margin. But then again I could argue: Why not put RAID0,1,10,4,5,6
    > into one big module? Makes no sense, huh?

    Makes perfect sense to me. Just modprobe raid.o and you have all
    raid levels available. That would make a lot of sense.

    > For me putting 5 and 6 into one
    > monolithic module makes no sense. A proper architecture would be to have some
    > common shared code (in a separate module?), not a monolithic big one.
    That's also a way, and certainly better than just splitting out raid6.

    Jesper Juhl <>
    Plain text mails only, please
    Don't top-post

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