Commit b1cbc6d4 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

writeback: make __wb_calc_thresh() take dirty_throttle_control 



wb_calc_thresh() calculates wb_thresh by scaling thresh according to
the wb's portion in the system-wide write bandwidth.  cgroup writeback
support would need to calculate wb_thresh against memcg domain too.
This patch renames wb_calc_thresh() to __wb_calc_thresh() and makes it
take dirty_throttle_control so that the function can later be updated
to calculate against different domains according to
dirty_throttle_control.

wb_calc_thresh() is now a thin wrapper around __wb_calc_thresh().

v2: The original version was incorrectly scaling dtc->dirty instead of
    dtc->thresh.  This was due to the extremely confusing function and
    variable names.  Added a rename patch and fixed this one.

Signed-off-by: default avatarTejun 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>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 970fb01a

mm/page-writeback.c

+14 −7
Original line number Diff line number Diff line
@@ -557,9 +557,8 @@ static unsigned long hard_dirty_limit(unsigned long thresh) 
}



/**

 * wb_calc_thresh - @wb's share of dirty throttling threshold

 * @wb: bdi_writeback to query

 * @dirty: global dirty limit in pages

 * __wb_calc_thresh - @wb's share of dirty throttling threshold

 * @dtc: dirty_throttle_context of interest

 *

 * Returns @wb's dirty limit in pages. The term "dirty" in the context of

 * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
@@ -578,9 +577,10 @@ static unsigned long hard_dirty_limit(unsigned long thresh) 
 * The wb's share of dirty limit will be adapting to its throughput and

 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.

 */

unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh)

static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc)

{

	struct wb_domain *dom = &global_wb_domain;

	unsigned long thresh = dtc->thresh;

	u64 wb_thresh;

	long numerator, denominator;

	unsigned long wb_min_ratio, wb_max_ratio;
@@ -588,14 +588,14 @@ unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) 
	/*

	 * Calculate this BDI's share of the thresh ratio.

	 */

	fprop_fraction_percpu(&dom->completions, &wb->completions,

	fprop_fraction_percpu(&dom->completions, &dtc->wb->completions,

			      &numerator, &denominator);



	wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100;

	wb_thresh *= numerator;

	do_div(wb_thresh, denominator);



	wb_min_max_ratio(wb, &wb_min_ratio, &wb_max_ratio);

	wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio);



	wb_thresh += (thresh * wb_min_ratio) / 100;

	if (wb_thresh > (thresh * wb_max_ratio) / 100)
@@ -604,6 +604,13 @@ unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh) 
	return wb_thresh;

}



unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh)

{

	struct dirty_throttle_control gdtc = { GDTC_INIT(wb),

					       .thresh = thresh };

	return __wb_calc_thresh(&gdtc);

}



/*

 *                           setpoint - dirty 3

 *        f(dirty) := 1.0 + (----------------)
@@ -1323,7 +1330,7 @@ static inline void wb_dirty_limits(struct dirty_throttle_control *dtc) 
	 *   wb_position_ratio() will let the dirtier task progress

	 *   at some rate <= (write_bw / 2) for bringing down wb_dirty.

	 */

	dtc->wb_thresh = wb_calc_thresh(dtc->wb, dtc->thresh);

	dtc->wb_thresh = __wb_calc_thresh(dtc);

	dtc->wb_bg_thresh = dtc->thresh ?

		div_u64((u64)dtc->wb_thresh * dtc->bg_thresh, dtc->thresh) : 0;

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