[PATCH 08/18] writeback: add dirty_throttle_control->pos_ratio
wb_position_ratio() is used to calculate pos_ratio, which is used for two purposes. wb_update_dirty_ratelimit() uses it to adjust wb->[balanced_]dirty_ratelimit gradually and balance_dirty_pages() to immediately adjust dirty_ratelimit right before applying it to determine pause duration. While wb_update_dirty_ratelimit() is separately rate limited from balance_dirty_pages(), on the run where the ratelimit is updated, we end up calculating pos_ratio twice with the same parameters. This patch adds dirty_throttle_control->pos_ratio. balance_dirty_pages() calculates it once per run and wb_update_dirty_ratelimit() uses the value stored in dirty_throttle_control. This removes the duplicate calculation and also will help implementing memcg wb_domain. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Wu Fengguang Cc: Greg Thelen --- mm/page-writeback.c | 36 +--- 1 file changed, 21 insertions(+), 15 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index a4b6dab..ac2d7b1 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -135,6 +135,8 @@ struct dirty_throttle_control { unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; unsigned long wb_bg_thresh; + + unsigned long pos_ratio; }; #define GDTC_INIT(__wb).wb = (__wb) @@ -717,7 +719,7 @@ static long long pos_ratio_polynom(unsigned long setpoint, * card's wb_dirty may rush to many times higher than wb_setpoint. * - the wb dirty thresh drops quickly due to change of JBOD workload */ -static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) +static void wb_position_ratio(struct dirty_throttle_control *dtc) { struct bdi_writeback *wb = dtc->wb; unsigned long write_bw = wb->avg_write_bandwidth; @@ -731,8 +733,10 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) long long pos_ratio;/* for scaling up/down the rate limit */ long x; + dtc->pos_ratio = 0; + if (unlikely(dtc->dirty >= limit)) - return 0; + return; /* * global setpoint @@ -770,18 +774,20 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { long long wb_pos_ratio; - if (dtc->wb_dirty < 8) - return min_t(long long, pos_ratio * 2, -2 << RATELIMIT_CALC_SHIFT); + if (dtc->wb_dirty < 8) { + dtc->pos_ratio = min_t(long long, pos_ratio * 2, + 2 << RATELIMIT_CALC_SHIFT); + return; + } if (dtc->wb_dirty >= wb_thresh) - return 0; + return; wb_setpoint = dirty_freerun_ceiling(wb_thresh, dtc->wb_bg_thresh); if (wb_setpoint == 0 || wb_setpoint == wb_thresh) - return 0; + return; wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc->wb_dirty, wb_thresh); @@ -807,7 +813,8 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) * is 2. We might want to tweak this if we observe the control * system is too slow to adapt. */ - return min(pos_ratio, wb_pos_ratio); + dtc->pos_ratio = min(pos_ratio, wb_pos_ratio); + return; } /* @@ -888,7 +895,7 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) pos_ratio *= 8; } - return pos_ratio; + dtc->pos_ratio = pos_ratio; } static void wb_update_write_bandwidth(struct bdi_writeback *wb, @@ -1009,7 +1016,6 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, unsigned long dirty_rate; unsigned long task_ratelimit; unsigned long balanced_dirty_ratelimit; - unsigned long pos_ratio; unsigned long step; unsigned long x; @@ -1019,12 +1025,11 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, */ dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed; - pos_ratio = wb_position_ratio(dtc); /* * task_ratelimit reflects each dd's dirty rate for the past 200ms. */ task_ratelimit = (u64)dirty_ratelimit * - pos_ratio >> RATELIMIT_CALC_SHIFT; + dtc->pos_ratio >> RATELIMIT_CALC_SHIFT; task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */
[PATCH 08/18] writeback: add dirty_throttle_control-pos_ratio
wb_position_ratio() is used to calculate pos_ratio, which is used for two purposes. wb_update_dirty_ratelimit() uses it to adjust wb-[balanced_]dirty_ratelimit gradually and balance_dirty_pages() to immediately adjust dirty_ratelimit right before applying it to determine pause duration. While wb_update_dirty_ratelimit() is separately rate limited from balance_dirty_pages(), on the run where the ratelimit is updated, we end up calculating pos_ratio twice with the same parameters. This patch adds dirty_throttle_control-pos_ratio. balance_dirty_pages() calculates it once per run and wb_update_dirty_ratelimit() uses the value stored in dirty_throttle_control. This removes the duplicate calculation and also will help implementing memcg wb_domain. Signed-off-by: Tejun Heo t...@kernel.org Cc: Jens Axboe ax...@kernel.dk Cc: Jan Kara j...@suse.cz Cc: Wu Fengguang fengguang...@intel.com Cc: Greg Thelen gthe...@google.com --- mm/page-writeback.c | 36 +--- 1 file changed, 21 insertions(+), 15 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index a4b6dab..ac2d7b1 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -135,6 +135,8 @@ struct dirty_throttle_control { unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; unsigned long wb_bg_thresh; + + unsigned long pos_ratio; }; #define GDTC_INIT(__wb).wb = (__wb) @@ -717,7 +719,7 @@ static long long pos_ratio_polynom(unsigned long setpoint, * card's wb_dirty may rush to many times higher than wb_setpoint. * - the wb dirty thresh drops quickly due to change of JBOD workload */ -static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) +static void wb_position_ratio(struct dirty_throttle_control *dtc) { struct bdi_writeback *wb = dtc-wb; unsigned long write_bw = wb-avg_write_bandwidth; @@ -731,8 +733,10 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) long long pos_ratio;/* for scaling up/down the rate limit */ long x; + dtc-pos_ratio = 0; + if (unlikely(dtc-dirty = limit)) - return 0; + return; /* * global setpoint @@ -770,18 +774,20 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) if (unlikely(wb-bdi-capabilities BDI_CAP_STRICTLIMIT)) { long long wb_pos_ratio; - if (dtc-wb_dirty 8) - return min_t(long long, pos_ratio * 2, -2 RATELIMIT_CALC_SHIFT); + if (dtc-wb_dirty 8) { + dtc-pos_ratio = min_t(long long, pos_ratio * 2, + 2 RATELIMIT_CALC_SHIFT); + return; + } if (dtc-wb_dirty = wb_thresh) - return 0; + return; wb_setpoint = dirty_freerun_ceiling(wb_thresh, dtc-wb_bg_thresh); if (wb_setpoint == 0 || wb_setpoint == wb_thresh) - return 0; + return; wb_pos_ratio = pos_ratio_polynom(wb_setpoint, dtc-wb_dirty, wb_thresh); @@ -807,7 +813,8 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) * is 2. We might want to tweak this if we observe the control * system is too slow to adapt. */ - return min(pos_ratio, wb_pos_ratio); + dtc-pos_ratio = min(pos_ratio, wb_pos_ratio); + return; } /* @@ -888,7 +895,7 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) pos_ratio *= 8; } - return pos_ratio; + dtc-pos_ratio = pos_ratio; } static void wb_update_write_bandwidth(struct bdi_writeback *wb, @@ -1009,7 +1016,6 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, unsigned long dirty_rate; unsigned long task_ratelimit; unsigned long balanced_dirty_ratelimit; - unsigned long pos_ratio; unsigned long step; unsigned long x; @@ -1019,12 +1025,11 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, */ dirty_rate = (dirtied - wb-dirtied_stamp) * HZ / elapsed; - pos_ratio = wb_position_ratio(dtc); /* * task_ratelimit reflects each dd's dirty rate for the past 200ms. */ task_ratelimit = (u64)dirty_ratelimit * - pos_ratio RATELIMIT_CALC_SHIFT; + dtc-pos_ratio RATELIMIT_CALC_SHIFT; task_ratelimit++; /* it