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    SubjectRe: spinlock usage - ext2_get_block, lru_list_lock
    Andreas Dilger wrote:
    > With per-group (or maybe per-bitmap) locking, files could be created in
    > parallel with only a small amount of global locking if they are in different
    > groups.

    ...and then we can let the disc go nuts seeking to actually commit all
    these new blocks. I suspect that this change would only be a win for
    memory-based discs where seek time is zero.

    I think that before anyone starts modifying the kernel for this they
    should benchmark how often the free block checker blocks on lock
    contention _AND_ how often the thread its contending with is looking
    for a free block in a _different_ allocation group. I bet it's not
    often at all.

    > It may also be
    > possible to have lazy updating of the superblock counts, and depend on
    > e2fsck to update the superblock counts on a crash.

    That sounds more promising.

    > , and only moving the deltas from the groups
    > to the superblock on sync or similar.

    If we're going to assume that e2fsck will correct the numbers anyway then
    there's really no reason to update them any time except when marking
    the filesystem clean (umount, remount-ro) As a bonus, we have to update
    the superblock then anyway.

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      Last update: 2005-03-22 13:29    [W:0.021 / U:16.364 seconds]
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