From: Tejun Heo <tj@kernel.org> To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, Tejun Heo <tj@kernel.org> Subject: [PATCH 06/18] writeback: add dirty_throttle_control->wb_bg_thresh Date: Mon, 23 Mar 2015 01:07:35 -0400 [thread overview] Message-ID: <1427087267-16592-7-git-send-email-tj@kernel.org> (raw) In-Reply-To: <1427087267-16592-1-git-send-email-tj@kernel.org> wb_bg_thresh is currently treated as a second-class citizen. It's only used when BDI_CAP_STRICTLIMIT is set and balance_dirty_pages() doesn't calculate it unless the cap is set. When the cap is set, the calculated value is not passed around but instead recalculated whenever it's used. wb_position_ratio() calculates it by scaling wb_thresh proportional to bg_thresh / thresh. wb_update_dirty_ratelimit() uses wb_dirty_limit() on bg_thresh, which should generally lead to a similar result as the proportional scaling but can also be way off in the presence of max/min_ratio settings. Avoiding wb_bg_thresh calculation saves us one u64 multiplication and divsion when BDI_CAP_STRICTLIMIT is not set. Given that balance_dirty_pages() is already ratelimited, this doesn't justify the incurred extra complexity. This patch adds wb_bg_thresh to dirty_throttle_control and makes wb_dirty_limits() always calculate it and updates the users to use the pre-calculated value. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Greg Thelen <gthelen@google.com> --- mm/page-writeback.c | 27 +++++++++++---------------- 1 file changed, 11 insertions(+), 16 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index b8e95a4..00218e9 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -134,6 +134,7 @@ struct dirty_throttle_control { unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; + unsigned long wb_bg_thresh; }; #define GDTC_INIT(__wb) .wb = (__wb) @@ -761,7 +762,6 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { long long wb_pos_ratio; - unsigned long wb_bg_thresh; if (dtc->wb_dirty < 8) return min_t(long long, pos_ratio * 2, @@ -770,9 +770,8 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) if (dtc->wb_dirty >= wb_thresh) return 0; - wb_bg_thresh = div_u64((u64)wb_thresh * dtc->bg_thresh, - dtc->thresh); - wb_setpoint = dirty_freerun_ceiling(wb_thresh, wb_bg_thresh); + wb_setpoint = dirty_freerun_ceiling(wb_thresh, + dtc->wb_bg_thresh); if (wb_setpoint == 0 || wb_setpoint == wb_thresh) return 0; @@ -1104,15 +1103,14 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, * * We rampup dirty_ratelimit forcibly if wb_dirty is low because * it's possible that wb_thresh is close to zero due to inactivity - * of backing device (see the implementation of wb_dirty_limit()). + * of backing device. */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { dirty = dtc->wb_dirty; if (dtc->wb_dirty < 8) setpoint = dtc->wb_dirty + 1; else - setpoint = (dtc->wb_thresh + - wb_dirty_limit(wb, dtc->bg_thresh)) / 2; + setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; } if (dirty < setpoint) { @@ -1307,8 +1305,7 @@ static long wb_min_pause(struct bdi_writeback *wb, return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; } -static inline void wb_dirty_limits(struct dirty_throttle_control *dtc, - unsigned long *wb_bg_thresh) +static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) { struct bdi_writeback *wb = dtc->wb; unsigned long wb_reclaimable; @@ -1327,11 +1324,8 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc, * at some rate <= (write_bw / 2) for bringing down wb_dirty. */ dtc->wb_thresh = wb_dirty_limit(dtc->wb, dtc->thresh); - - if (wb_bg_thresh) - *wb_bg_thresh = dtc->thresh ? div_u64((u64)dtc->wb_thresh * - dtc->bg_thresh, - dtc->thresh) : 0; + dtc->wb_bg_thresh = dtc->thresh ? + div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; /* * In order to avoid the stacked BDI deadlock we need @@ -1396,10 +1390,11 @@ static void balance_dirty_pages(struct address_space *mapping, global_dirty_limits(&gdtc->bg_thresh, &gdtc->thresh); if (unlikely(strictlimit)) { - wb_dirty_limits(gdtc, &bg_thresh); + wb_dirty_limits(gdtc); dirty = gdtc->wb_dirty; thresh = gdtc->wb_thresh; + bg_thresh = gdtc->wb_bg_thresh; } else { dirty = gdtc->dirty; thresh = gdtc->thresh; @@ -1427,7 +1422,7 @@ static void balance_dirty_pages(struct address_space *mapping, wb_start_background_writeback(wb); if (!strictlimit) - wb_dirty_limits(gdtc, NULL); + wb_dirty_limits(gdtc); dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && ((gdtc->dirty > gdtc->thresh) || strictlimit); -- 2.1.0
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org> To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, Tejun Heo <tj@kernel.org> Subject: [PATCH 06/18] writeback: add dirty_throttle_control->wb_bg_thresh Date: Mon, 23 Mar 2015 01:07:35 -0400 [thread overview] Message-ID: <1427087267-16592-7-git-send-email-tj@kernel.org> (raw) In-Reply-To: <1427087267-16592-1-git-send-email-tj@kernel.org> wb_bg_thresh is currently treated as a second-class citizen. It's only used when BDI_CAP_STRICTLIMIT is set and balance_dirty_pages() doesn't calculate it unless the cap is set. When the cap is set, the calculated value is not passed around but instead recalculated whenever it's used. wb_position_ratio() calculates it by scaling wb_thresh proportional to bg_thresh / thresh. wb_update_dirty_ratelimit() uses wb_dirty_limit() on bg_thresh, which should generally lead to a similar result as the proportional scaling but can also be way off in the presence of max/min_ratio settings. Avoiding wb_bg_thresh calculation saves us one u64 multiplication and divsion when BDI_CAP_STRICTLIMIT is not set. Given that balance_dirty_pages() is already ratelimited, this doesn't justify the incurred extra complexity. This patch adds wb_bg_thresh to dirty_throttle_control and makes wb_dirty_limits() always calculate it and updates the users to use the pre-calculated value. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Greg Thelen <gthelen@google.com> --- mm/page-writeback.c | 27 +++++++++++---------------- 1 file changed, 11 insertions(+), 16 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index b8e95a4..00218e9 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -134,6 +134,7 @@ struct dirty_throttle_control { unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; + unsigned long wb_bg_thresh; }; #define GDTC_INIT(__wb) .wb = (__wb) @@ -761,7 +762,6 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { long long wb_pos_ratio; - unsigned long wb_bg_thresh; if (dtc->wb_dirty < 8) return min_t(long long, pos_ratio * 2, @@ -770,9 +770,8 @@ static unsigned long wb_position_ratio(struct dirty_throttle_control *dtc) if (dtc->wb_dirty >= wb_thresh) return 0; - wb_bg_thresh = div_u64((u64)wb_thresh * dtc->bg_thresh, - dtc->thresh); - wb_setpoint = dirty_freerun_ceiling(wb_thresh, wb_bg_thresh); + wb_setpoint = dirty_freerun_ceiling(wb_thresh, + dtc->wb_bg_thresh); if (wb_setpoint == 0 || wb_setpoint == wb_thresh) return 0; @@ -1104,15 +1103,14 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc, * * We rampup dirty_ratelimit forcibly if wb_dirty is low because * it's possible that wb_thresh is close to zero due to inactivity - * of backing device (see the implementation of wb_dirty_limit()). + * of backing device. */ if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) { dirty = dtc->wb_dirty; if (dtc->wb_dirty < 8) setpoint = dtc->wb_dirty + 1; else - setpoint = (dtc->wb_thresh + - wb_dirty_limit(wb, dtc->bg_thresh)) / 2; + setpoint = (dtc->wb_thresh + dtc->wb_bg_thresh) / 2; } if (dirty < setpoint) { @@ -1307,8 +1305,7 @@ static long wb_min_pause(struct bdi_writeback *wb, return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; } -static inline void wb_dirty_limits(struct dirty_throttle_control *dtc, - unsigned long *wb_bg_thresh) +static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) { struct bdi_writeback *wb = dtc->wb; unsigned long wb_reclaimable; @@ -1327,11 +1324,8 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc, * at some rate <= (write_bw / 2) for bringing down wb_dirty. */ dtc->wb_thresh = wb_dirty_limit(dtc->wb, dtc->thresh); - - if (wb_bg_thresh) - *wb_bg_thresh = dtc->thresh ? div_u64((u64)dtc->wb_thresh * - dtc->bg_thresh, - dtc->thresh) : 0; + dtc->wb_bg_thresh = dtc->thresh ? + div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0; /* * In order to avoid the stacked BDI deadlock we need @@ -1396,10 +1390,11 @@ static void balance_dirty_pages(struct address_space *mapping, global_dirty_limits(&gdtc->bg_thresh, &gdtc->thresh); if (unlikely(strictlimit)) { - wb_dirty_limits(gdtc, &bg_thresh); + wb_dirty_limits(gdtc); dirty = gdtc->wb_dirty; thresh = gdtc->wb_thresh; + bg_thresh = gdtc->wb_bg_thresh; } else { dirty = gdtc->dirty; thresh = gdtc->thresh; @@ -1427,7 +1422,7 @@ static void balance_dirty_pages(struct address_space *mapping, wb_start_background_writeback(wb); if (!strictlimit) - wb_dirty_limits(gdtc, NULL); + wb_dirty_limits(gdtc); dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) && ((gdtc->dirty > gdtc->thresh) || strictlimit); -- 2.1.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-03-23 5:13 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-03-23 5:07 [PATCHSET 2/3 block/for-4.1/core] writeback: cgroup writeback backpressure propagation Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 01/18] memcg: make mem_cgroup_read_{stat|event}() iterate possible cpus instead of online Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-25 22:39 ` [PATCH 1.5/18] writeback: clean up wb_dirty_limit() Tejun Heo 2015-03-25 22:39 ` Tejun Heo 2015-03-25 22:39 ` Tejun Heo 2015-03-25 22:39 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 02/18] writeback: reorganize [__]wb_update_bandwidth() Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 03/18] writeback: implement wb_domain Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 04/18] writeback: move global_dirty_limit into wb_domain Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 05/18] writeback: consolidate dirty throttle parameters into dirty_throttle_control Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` Tejun Heo [this message] 2015-03-23 5:07 ` [PATCH 06/18] writeback: add dirty_throttle_control->wb_bg_thresh Tejun Heo 2015-03-23 5:07 ` [PATCH 07/18] writeback: make __wb_dirty_limit() take dirty_throttle_control Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-25 22:42 ` [PATCH v2 07/18] writeback: make __wb_calc_thresh() " Tejun Heo 2015-03-25 22:42 ` Tejun Heo 2015-03-25 22:42 ` Tejun Heo 2015-03-25 22:42 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 08/18] writeback: add dirty_throttle_control->pos_ratio Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 09/18] writeback: add dirty_throttle_control->wb_completions Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 10/18] writeback: add dirty_throttle_control->dom Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 11/18] writeback: make __wb_writeout_inc() and hard_dirty_limit() take wb_domaas a parameter Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 12/18] writeback: separate out domain_dirty_limits() Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 13/18] writeback: move over_bground_thresh() to mm/page-writeback.c Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 14/18] writeback: update wb_over_bg_thresh() to use wb_domain aware operations Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 15/18] writeback: implement memcg wb_domain Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 16/18] writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 17/18] writeback: implement memcg writeback domain based throttling Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:07 ` [PATCH 18/18] mm: vmscan: remove memcg stalling on writeback pages during direct reclaim Tejun Heo 2015-03-23 5:07 ` Tejun Heo 2015-03-23 5:27 ` Tejun Heo 2015-03-23 5:27 ` Tejun Heo 2015-03-25 22:26 ` [PATCH v2 18/18] mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use Tejun Heo 2015-03-25 22:26 ` Tejun Heo 2015-03-25 22:26 ` Tejun Heo 2015-03-25 22:26 ` Tejun Heo
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