[lkml]   [2007]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [RFC] Heads up on sys_fallocate()
    On Mon, Mar 05, 2007 at 07:15:33AM -0800, Ulrich Drepper wrote:
    > Well, I'm sure the kernel can do better than the code we have in libc
    > now. The kernel has access to the bitmasks which say which blocks have
    > already been allocated. The libc code does not and we have to be very
    > simple-minded and simply touch every block. And this means reading it
    > and then writing it back. The kernel would know when the reading part
    > is not necessary. Add to then the block granularity (we use f_bsize as
    > returned from fstatfs but that's not the best value in some cases) and
    > you have compelling data to have generic code in the kernel. Then libc
    > implementation can then go away completely which is a good thing.

    You have a very good point; indeed since we don't export an interface
    which allows userspace to determine whether or not a block is in use,
    that does mean a huge amount of churn in the page cache. So maybe it
    would be worth doing in the kernel as a result, although the libc
    implementation still wouldn't be able to go away for long time due to
    the need to be backwards compatible with older kernels that didn't
    have this support.


    - Ted
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2007-03-05 17:09    [W:0.020 / U:0.056 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site