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Subject[PATCH 02/13] writeback: consolidate variable names in balance_dirty_pages()
Lots of lenthy tests.. Let's compact the names

*_dirty = NR_FILE_DIRTY + NR_WRITEBACK + NR_UNSTABLE_NFS

balance_dirty_pages() only cares about the above dirty sum except
in one place -- on starting background writeback.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-11-15 19:50:16.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-11-15 19:50:27.000000000 +0800
@@ -461,8 +461,8 @@ unsigned long bdi_dirty_limit(struct bac
static void balance_dirty_pages(struct address_space *mapping,
unsigned long pages_dirtied)
{
- long nr_reclaimable, bdi_nr_reclaimable;
- long nr_writeback, bdi_nr_writeback;
+ long nr_reclaimable;
+ long nr_dirty, bdi_dirty; /* = file_dirty + writeback + unstable_nfs */
unsigned long background_thresh;
unsigned long dirty_thresh;
unsigned long bdi_thresh;
@@ -480,7 +480,7 @@ static void balance_dirty_pages(struct a
*/
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
- nr_writeback = global_page_state(NR_WRITEBACK);
+ nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);

global_dirty_limits(&background_thresh, &dirty_thresh);

@@ -489,8 +489,7 @@ static void balance_dirty_pages(struct a
* catch-up. This avoids (excessively) small writeouts
* when the bdi limits are ramping up.
*/
- if (nr_reclaimable + nr_writeback <=
- (background_thresh + dirty_thresh) / 2)
+ if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
break;

bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
@@ -507,21 +506,21 @@ static void balance_dirty_pages(struct a
* deltas.
*/
if (bdi_thresh < 2*bdi_stat_error(bdi)) {
- bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
- bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
+ bdi_dirty = bdi_stat_sum(bdi, BDI_RECLAIMABLE) +
+ bdi_stat_sum(bdi, BDI_WRITEBACK);
} else {
- bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
- bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+ bdi_dirty = bdi_stat(bdi, BDI_RECLAIMABLE) +
+ bdi_stat(bdi, BDI_WRITEBACK);
}

- if (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh) {
+ if (bdi_dirty >= bdi_thresh) {
pause = HZ/10;
goto pause;
}

bw = 100 << 20; /* use static 100MB/s for the moment */

- bw = bw * (bdi_thresh - (bdi_nr_reclaimable + bdi_nr_writeback));
+ bw = bw * (bdi_thresh - bdi_dirty);
bw = bw / (bdi_thresh / TASK_SOFT_DIRTY_LIMIT + 1);

pause = HZ * (pages_dirtied << PAGE_CACHE_SHIFT) / (bw + 1);
@@ -537,9 +536,8 @@ pause:
* bdi or process from holding back light ones; The latter is
* the last resort safeguard.
*/
- dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
- || (nr_reclaimable + nr_writeback > dirty_thresh);
+ dirty_exceeded = (bdi_dirty > bdi_thresh) ||
+ (nr_dirty > dirty_thresh);

if (!dirty_exceeded)
break;



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