• Liu Bo's avatar
    Btrfs: remove nr_async_bios · f851689b
    Liu Bo authored
    This was intended to congest higher layers to not send bios, but as
    
    1) the congested bit has been taken by writeback
    
    Async bios come from buffered writes and DIO writes.
    
    For DIO writes, we want to submit them ASAP, while for buffered writes,
    writeback uses balance_dirty_pages() to throttle how much dirty pages we
    can have.
    
    2) and no one is waiting for %nr_async_bios down to zero,
    
    Historically, it was introduced along with changes which let
    checksumming workload spread accross different cpus.  And at that time,
    pdflush was used instead of per-bdi flushing, perhaps pdflush did not
    have the necessary information for writeback to do throttling.
    
    We can safely remove them now.
    Signed-off-by: default avatarLiu Bo <bo.li.liu@oracle.com>
    [ additional explanation from mails, removed unused variable 'limit' ]
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    f851689b
disk-io.c 121 KB