From: Tang Junhui <tang.junhui@xxxxxxxxxx> Hello Coly: >It is because of ca->set->error_decay. When error_decay is set, bcache >tries to do an exponential decay for error count. That is, error numbers >is decaying against the quantity of io count, this is to avoid long time >accumulated errors exceeds error_limit and trigger bch_cache_set_error(). > >The I/O error counter, uses most significant 12 bits to record real >errors number. And too many I/Os may decay the errors number too fast, >so left shit it by 20 bits to make sure there are still enough errors >number after a while (e.g. the halflife). > >The we don't use the left shifting, when error_deay is set, and too many >I/Os happen, after a small piece of time, number of I/O errors will be >decayed too fast to reach error_limit. Therefore IMHO the left shifting >is necessary. > >BTW, I doubt whether current exponential error decay in >bch_count_io_errors() works properly. Because I don't catch the >connection between IO counter (ca->io_count) and error counter >(ca->io_errors). By default ca->set->error_decay is 0, so I doubt how >many people use/test this piece of code. (Maybe I am wrong) OK, LGTM. Reviewed-by: Tang Junhui <tang.junhui@xxxxxxxxxx> And ping Mike? Thanks, Tang Junhui
