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Subject[PATCH 21/21] Remove useless struct wbs
Subject: zoned vm counters: remove useless writeback structure
From: Christoph Lameter <clameter@sgi.com>

Remove writeback state

We can remove some functions now that were needed to calculate the page state
for writeback control since these statistics are now directly available.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Index: linux-2.6.17-rc6-cl/mm/page-writeback.c
===================================================================
--- linux-2.6.17-rc6-cl.orig/mm/page-writeback.c 2006-06-13 17:16:41.187504717 -0700
+++ linux-2.6.17-rc6-cl/mm/page-writeback.c 2006-06-13 17:18:26.555990446 -0700
@@ -99,23 +99,6 @@ EXPORT_SYMBOL(laptop_mode);

static void background_writeout(unsigned long _min_pages);

-struct writeback_state
-{
- unsigned long nr_dirty;
- unsigned long nr_unstable;
- unsigned long nr_mapped;
- unsigned long nr_writeback;
-};
-
-static void get_writeback_state(struct writeback_state *wbs)
-{
- wbs->nr_dirty = global_page_state(NR_DIRTY);
- wbs->nr_unstable = global_page_state(NR_UNSTABLE);
- wbs->nr_mapped = global_page_state(NR_MAPPED) +
- global_page_state(NR_ANON);
- wbs->nr_writeback = global_page_state(NR_WRITEBACK);
-}
-
/*
* Work out the current dirty-memory clamping and background writeout
* thresholds.
@@ -134,8 +117,8 @@ static void get_writeback_state(struct w
* clamping level.
*/
static void
-get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
- struct address_space *mapping)
+get_dirty_limits(long *pbackground, long *pdirty,
+ struct address_space *mapping)
{
int background_ratio; /* Percentages */
int dirty_ratio;
@@ -145,8 +128,6 @@ get_dirty_limits(struct writeback_state
unsigned long available_memory = total_pages;
struct task_struct *tsk;

- get_writeback_state(wbs);
-
#ifdef CONFIG_HIGHMEM
/*
* If this mapping can only allocate from low memory,
@@ -157,7 +138,9 @@ get_dirty_limits(struct writeback_state
#endif


- unmapped_ratio = 100 - (wbs->nr_mapped * 100) / total_pages;
+ unmapped_ratio = 100 - ((global_page_state(NR_MAPPED) +
+ global_page_state(NR_ANON)) * 100) /
+ total_pages;

dirty_ratio = vm_dirty_ratio;
if (dirty_ratio > unmapped_ratio / 2)
@@ -190,7 +173,6 @@ get_dirty_limits(struct writeback_state
*/
static void balance_dirty_pages(struct address_space *mapping)
{
- struct writeback_state wbs;
long nr_reclaimable;
long background_thresh;
long dirty_thresh;
@@ -208,11 +190,12 @@ static void balance_dirty_pages(struct a
.range_cyclic = 1,
};

- get_dirty_limits(&wbs, &background_thresh,
- &dirty_thresh, mapping);
- nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
- if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
- break;
+ get_dirty_limits(&background_thresh, &dirty_thresh, mapping);
+ nr_reclaimable = global_page_state(NR_DIRTY) +
+ global_page_state(NR_UNSTABLE);
+ if (nr_reclaimable + global_page_state(NR_WRITEBACK) <=
+ dirty_thresh)
+ break;

if (!dirty_exceeded)
dirty_exceeded = 1;
@@ -225,11 +208,14 @@ static void balance_dirty_pages(struct a
*/
if (nr_reclaimable) {
writeback_inodes(&wbc);
- get_dirty_limits(&wbs, &background_thresh,
- &dirty_thresh, mapping);
- nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
- if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
- break;
+ get_dirty_limits(&background_thresh,
+ &dirty_thresh, mapping);
+ nr_reclaimable = global_page_state(NR_DIRTY) +
+ global_page_state(NR_UNSTABLE);
+ if (nr_reclaimable +
+ global_page_state(NR_WRITEBACK)
+ <= dirty_thresh)
+ break;
pages_written += write_chunk - wbc.nr_to_write;
if (pages_written >= write_chunk)
break; /* We've done our duty */
@@ -237,8 +223,9 @@ static void balance_dirty_pages(struct a
blk_congestion_wait(WRITE, HZ/10);
}

- if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh && dirty_exceeded)
- dirty_exceeded = 0;
+ if (nr_reclaimable + global_page_state(NR_WRITEBACK)
+ <= dirty_thresh && dirty_exceeded)
+ dirty_exceeded = 0;

if (writeback_in_progress(bdi))
return; /* pdflush is already working this queue */
@@ -300,12 +287,11 @@ EXPORT_SYMBOL(balance_dirty_pages_rateli

void throttle_vm_writeout(void)
{
- struct writeback_state wbs;
long background_thresh;
long dirty_thresh;

for ( ; ; ) {
- get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
+ get_dirty_limits(&background_thresh, &dirty_thresh, NULL);

/*
* Boost the allowable dirty threshold a bit for page
@@ -313,8 +299,9 @@ void throttle_vm_writeout(void)
*/
dirty_thresh += dirty_thresh / 10; /* wheeee... */

- if (wbs.nr_unstable + wbs.nr_writeback <= dirty_thresh)
- break;
+ if (global_page_state(NR_UNSTABLE) +
+ global_page_state(NR_WRITEBACK) <= dirty_thresh)
+ break;
blk_congestion_wait(WRITE, HZ/10);
}
}
@@ -337,12 +324,12 @@ static void background_writeout(unsigned
};

for ( ; ; ) {
- struct writeback_state wbs;
long background_thresh;
long dirty_thresh;

- get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
- if (wbs.nr_dirty + wbs.nr_unstable < background_thresh
+ get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
+ if (global_page_state(NR_DIRTY) +
+ global_page_state(NR_UNSTABLE) < background_thresh
&& min_pages <= 0)
break;
wbc.encountered_congestion = 0;
@@ -366,12 +353,9 @@ static void background_writeout(unsigned
*/
int wakeup_pdflush(long nr_pages)
{
- if (nr_pages == 0) {
- struct writeback_state wbs;
-
- get_writeback_state(&wbs);
- nr_pages = wbs.nr_dirty + wbs.nr_unstable;
- }
+ if (nr_pages == 0)
+ nr_pages = global_page_state(NR_DIRTY) +
+ global_page_state(NR_UNSTABLE);
return pdflush_operation(background_writeout, nr_pages);
}

@@ -402,7 +386,6 @@ static void wb_kupdate(unsigned long arg
unsigned long start_jif;
unsigned long next_jif;
long nr_to_write;
- struct writeback_state wbs;
struct writeback_control wbc = {
.bdi = NULL,
.sync_mode = WB_SYNC_NONE,
@@ -415,11 +398,11 @@ static void wb_kupdate(unsigned long arg

sync_supers();

- get_writeback_state(&wbs);
oldest_jif = jiffies - dirty_expire_interval;
start_jif = jiffies;
next_jif = start_jif + dirty_writeback_interval;
- nr_to_write = wbs.nr_dirty + wbs.nr_unstable +
+ nr_to_write = global_page_state(NR_DIRTY) +
+ global_page_state(NR_UNSTABLE) +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
while (nr_to_write > 0) {
wbc.encountered_congestion = 0;
-
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