[PATCH 1.5/18] writeback: clean up wb_dirty_limit()

Tejun Heo
2015-03-25T22:39:57Z

>From e28d6181cb196846ca64870137fe157351a5b029 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 25 Mar 2015 18:34:35 -0400

The function name wb_dirty_limit(), its argument @dirty and the local
variable @wb_dirty are mortally confusing given that the function
calculates per-wb threshold value not dirty pages, especially given
that @dirty and @wb_dirty are used elsewhere for dirty pages.

Let's rename the function to wb_calc_thresh() and wb_dirty to
wb_thresh.

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>
---
The rewview git branch has been updated accordingly.

git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-cgroup-writeback-backpressure-20150322

This creates quite a few conflicts down the series. Please use the
git branch for testing. I'll post v2 series once I get more feedback.

Thanks.

fs/fs-writeback.c | 2 +-
include/linux/writeback.h | 2 +-
mm/backing-dev.c | 6 +++---
mm/page-writeback.c | 30 +++++++++++++++---------------
4 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 890cff1..5e6f2dd 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1072,7 +1072,7 @@ static bool over_bground_thresh(struct bdi_writeback *wb)
global_page_state(NR_UNSTABLE_NFS) > background_thresh)
return true;

- if (wb_stat(wb, WB_RECLAIMABLE) > wb_dirty_limit(wb, background_thresh))
+ if (wb_stat(wb, WB_RECLAIMABLE) > wb_calc_thresh(wb, background_thresh))
return true;

return false;
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 75349bb..6f6b8c8 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -152,7 +152,7 @@ int dirty_writeback_centisecs_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);

void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
-unsigned long wb_dirty_limit(struct bdi_writeback *wb, unsigned long dirty);
+unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);

void __wb_update_bandwidth(struct bdi_writeback *wb,
unsigned long thresh,
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index ad5608d..9c8b7b5 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -49,7 +49,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
struct bdi_writeback *wb = &bdi->wb;
unsigned long background_thresh;
unsigned long dirty_thresh;
- unsigned long bdi_thresh;
+ unsigned long wb_thresh;
unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
struct inode *inode;

@@ -67,7 +67,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
spin_unlock(&wb->list_lock);

global_dirty_limits(&background_thresh, &dirty_thresh);
- bdi_thresh = wb_dirty_limit(wb, dirty_thresh);
+ wb_thresh = wb_calc_thresh(wb, dirty_thresh);

#define K(x) ((x) << (PAGE_SHIFT - 10))
seq_printf(m,
@@ -87,7 +87,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
"state: %10lx\n",
(unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
(unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
- K(bdi_thresh),
+ K(wb_thresh),
K(dirty_thresh),
K(background_thresh),
(unsigned long) K(wb_stat(wb, WB_DIRTIED)),
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 1767658..3401634 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -556,7 +556,7 @@ static unsigned long hard_dirty_limit(unsigned long thresh)
}

/**
- * wb_dirty_limit - @wb's share of dirty throttling threshold
+ * wb_calc_thresh - @wb's share of dirty throttling threshold
* @wb: bdi_writeback to query
* @dirty: global dirty limit in pages
*
@@ -577,28 +577,28 @@ 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_dirty_limit(struct bdi_writeback *wb, unsigned long dirty)
+unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh)
{
- u64 wb_dirty;
+ u64 wb_thresh;
long numerator, denominator;
unsigned long wb_min_ratio, wb_max_ratio;

/*
- * Calculate this BDI's share of the dirty ratio.
+ * Calculate this BDI's share of the thresh ratio.
*/
wb_writeout_fraction(wb, &numerator, &denominator);

- wb_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
- wb_dirty *= numerator;
- do_div(wb_dirty, 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_dirty += (dirty * wb_min_ratio) / 100;
- if (wb_dirty > (dirty * wb_max_ratio) / 100)
- wb_dirty = dirty * wb_max_ratio / 100;
+ wb_thresh += (thresh * wb_min_ratio) / 100;
+ if (wb_thresh > (thresh * wb_max_ratio) / 100)
+ wb_thresh = thresh * wb_max_ratio / 100;

- return wb_dirty;
+ return wb_thresh;
}

/*
@@ -750,7 +750,7 @@ static unsigned long wb_position_ratio(struct bdi_writeback *wb,
* total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global
* limits are set by default to 10% and 20% (background and throttle).
* Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages.
- * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. wb_setpoint is
+ * wb_calc_thresh(wb, bg_thresh) is about ~4K pages. wb_setpoint is
* about ~6K pages (as the average of background and throttle wb
* limits). The 3rd order polynomial will provide positive feedback if
* wb_dirty is under wb_setpoint and vice versa.
@@ -1115,7 +1115,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
*
* 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 (see the implementation of wb_calc_thresh()).
*/
if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
dirty = wb_dirty;
@@ -1123,7 +1123,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
setpoint = wb_dirty + 1;
else
setpoint = (wb_thresh +
- wb_dirty_limit(wb, bg_thresh)) / 2;
+ wb_calc_thresh(wb, bg_thresh)) / 2;
}

if (dirty < setpoint) {
@@ -1352,7 +1352,7 @@ static inline void wb_dirty_limits(struct bdi_writeback *wb,
* wb_position_ratio() will let the dirtier task progress
* at some rate <= (write_bw / 2) for bringing down wb_dirty.
*/
- *wb_thresh = wb_dirty_limit(wb, dirty_thresh);
+ *wb_thresh = wb_calc_thresh(wb, dirty_thresh);

if (wb_bg_thresh)
*wb_bg_thresh = dirty_thresh ? div_u64((u64)*wb_thresh *
--
2.1.0