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SubjectRe: [PATCH] writeback: Per-block device bdi->dirty_writeback_interval and bdi->dirty_expire_interval.
Kautuk,

Here is a quick demo for bdi->dirty_background_time. Totally untested.

Thanks,
Fengguang

---
fs/fs-writeback.c | 16 +++++++++++-----
include/linux/backing-dev.h | 1 +
include/linux/writeback.h | 1 +
mm/backing-dev.c | 23 +++++++++++++++++++++++
mm/page-writeback.c | 3 ++-
5 files changed, 38 insertions(+), 6 deletions(-)
--- linux-next.orig/fs/fs-writeback.c 2011-08-19 13:59:41.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2011-08-19 14:00:36.000000000 +0800
@@ -653,14 +653,20 @@ long writeback_inodes_wb(struct bdi_writ
return nr_pages - work.nr_pages;
}

-static inline bool over_bground_thresh(void)
+bool over_bground_thresh(struct backing_dev_info *bdi)
{
unsigned long background_thresh, dirty_thresh;

global_dirty_limits(&background_thresh, &dirty_thresh);

- return (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) > background_thresh);
+ if (global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS) > background_thresh)
+ return true;
+
+ background_thresh = bdi->avg_write_bandwidth *
+ (u64)bdi->dirty_background_time / 1000;
+
+ return bdi_stat(bdi, BDI_RECLAIMABLE) > background_thresh;
}

/*
@@ -722,7 +728,7 @@ static long wb_writeback(struct bdi_writ
* For background writeout, stop when we are below the
* background dirty threshold
*/
- if (work->for_background && !over_bground_thresh())
+ if (work->for_background && !over_bground_thresh(wb->bdi))
break;

if (work->for_kupdate) {
@@ -806,7 +812,7 @@ static unsigned long get_nr_dirty_pages(

static long wb_check_background_flush(struct bdi_writeback *wb)
{
- if (over_bground_thresh()) {
+ if (over_bground_thresh(wb->bdi)) {

struct wb_writeback_work work = {
.nr_pages = LONG_MAX,
--- linux-next.orig/include/linux/backing-dev.h 2011-08-19 13:59:41.000000000 +0800
+++ linux-next/include/linux/backing-dev.h 2011-08-19 14:00:07.000000000 +0800
@@ -91,6 +91,7 @@ struct backing_dev_info {

unsigned int min_ratio;
unsigned int max_ratio, max_prop_frac;
+ unsigned int dirty_background_time;

struct bdi_writeback wb; /* default writeback info for this bdi */
spinlock_t wb_lock; /* protects work_list */
--- linux-next.orig/mm/backing-dev.c 2011-08-19 13:59:41.000000000 +0800
+++ linux-next/mm/backing-dev.c 2011-08-19 14:03:15.000000000 +0800
@@ -225,12 +225,33 @@ static ssize_t max_ratio_store(struct de
}
BDI_SHOW(max_ratio, bdi->max_ratio)

+static ssize_t dirty_background_time_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct backing_dev_info *bdi = dev_get_drvdata(dev);
+ char *end;
+ unsigned int ms;
+ ssize_t ret = -EINVAL;
+
+ ms = simple_strtoul(buf, &end, 10);
+ if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
+ bdi->dirty_background_time = ms;
+ if (!ret)
+ ret = count;
+ if (over_bground_thresh(bdi))
+ bdi_start_background_writeback(bdi);
+ }
+ return ret;
+}
+BDI_SHOW(dirty_background_time, bdi->dirty_background_time)
+
#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)

static struct device_attribute bdi_dev_attrs[] = {
__ATTR_RW(read_ahead_kb),
__ATTR_RW(min_ratio),
__ATTR_RW(max_ratio),
+ __ATTR_RW(dirty_background_time),
__ATTR_NULL,
};

@@ -657,6 +678,8 @@ int bdi_init(struct backing_dev_info *bd
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = PROP_FRAC_BASE;
+ bdi->dirty_background_time = 10000;
+
spin_lock_init(&bdi->wb_lock);
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->work_list);
--- linux-next.orig/mm/page-writeback.c 2011-08-19 14:00:07.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-08-19 14:00:07.000000000 +0800
@@ -1163,7 +1163,8 @@ pause:
if (laptop_mode)
return;

- if (nr_reclaimable > background_thresh)
+ if (nr_reclaimable > background_thresh ||
+ over_bground_thresh(bdi))
bdi_start_background_writeback(bdi);
}

--- linux-next.orig/include/linux/writeback.h 2011-08-19 14:00:41.000000000 +0800
+++ linux-next/include/linux/writeback.h 2011-08-19 14:01:19.000000000 +0800
@@ -132,6 +132,7 @@ extern int block_dump;
extern int laptop_mode;

extern unsigned long determine_dirtyable_memory(void);
+extern bool over_bground_thresh(struct backing_dev_info *bdi);

extern int dirty_background_ratio_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,

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