WB_FRN_HIST_SLOTS  238 fs/fs-writeback.c #define WB_FRN_HIST_UNIT	(WB_FRN_TIME_PERIOD / WB_FRN_HIST_SLOTS)
WB_FRN_HIST_SLOTS  240 fs/fs-writeback.c #define WB_FRN_HIST_THR_SLOTS	(WB_FRN_HIST_SLOTS / 2)