On Fri, Feb 14, 2020 at 1:50 PM Bart Van Assche <bvanassche@xxxxxxx> wrote: > > On 2020-02-13 11:21, Salman Qazi wrote: > > AFAICT, This is not actually sufficient, because the issuer of the bio > > is waiting for the entire bio, regardless of how it is split later. > > But, also there isn't a good mapping between the size of the secure > > discard and how long it will take. If given the geometry of a flash > > device, it is not hard to construct a scenario where a relatively > > small secure discard (few thousand sectors) will take a very long time > > (multiple seconds). > > > > Having said that, I don't like neutering the hung task timer either. > > Hi Salman, > > How about modifying the block layer such that completions of bio > fragments are considered as task activity? I think that bio splitting is > rare enough for such a change not to affect performance of the hot path. Are you sure that the task hung warning won't be triggered in case of non-splitting? > > How about setting max_discard_segments such that a discard always > completes in less than half the hung task timeout? This may make > discards a bit slower for one particular block driver but I think that's > better than hung task complaints. I am afraid you can't find a golden setting max_discard_segments working for every drivers. Even it is found, the performance may have been affected. So just wondering why not take the simple approach used in blk_execute_rq()? Thanks, Ming Lei
