• Jens Axboe's avatar
    blk-wbt: add general throttling mechanism · e34cbd30
    Jens Axboe authored
    We can hook this up to the block layer, to help throttle buffered
    writes.
    
    wbt registers a few trace points that can be used to track what is
    happening in the system:
    
    wbt_lat: 259:0: latency 2446318
    wbt_stat: 259:0: rmean=2446318, rmin=2446318, rmax=2446318, rsamples=1,
                   wmean=518866, wmin=15522, wmax=5330353, wsamples=57
    wbt_step: 259:0: step down: step=1, window=72727272, background=8, normal=16, max=32
    
    This shows a sync issue event (wbt_lat) that exceeded it's time. wbt_stat
    dumps the current read/write stats for that window, and wbt_step shows a
    step down event where we now scale back writes. Each trace includes the
    device, 259:0 in this case.
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    e34cbd30
wbt.h 3.69 KB