• Josef Bacik's avatar
    btrfs: track DIO bytes in flight · 4297ff84
    Josef Bacik authored
    When diagnosing a slowdown of generic/224 I noticed we were not doing
    anything when calling into shrink_delalloc().  This is because all
    writes in 224 are O_DIRECT, not delalloc, and thus our delalloc_bytes
    counter is 0, which short circuits most of the work inside of
    shrink_delalloc().  However O_DIRECT writes still consume metadata
    resources and generate ordered extents, which we can still wait on.
    
    Fix this by tracking outstanding DIO write bytes, and use this as well
    as the delalloc bytes counter to decide if we need to lookup and wait on
    any ordered extents.  If we have more DIO writes than delalloc bytes
    we'll go ahead and wait on any ordered extents regardless of our flush
    state as flushing delalloc is likely to not gain us anything.
    Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
    [ use dio instead of odirect in identifiers ]
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    4297ff84
ctree.h 129 KB