writeback: move global_dirty_limit into wb_domain
This patch is a part of the series to define wb_domain which
represents a domain that wb's (bdi_writeback's) belong to and are
measured against each other in. This will enable IO backpressure
propagation for cgroup writeback.
global_dirty_limit exists to regulate the global dirty threshold which
is a property of the wb_domain. This patch moves hard_dirty_limit,
dirty_lock, and update_time into wb_domain.
This is pure reorganization and doesn't introduce any behavioral
changes.
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>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 08e1737..27e60ba 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -122,9 +122,7 @@
/* End of sysctl-exported parameters */
-unsigned long global_dirty_limit;
-
-static struct wb_domain global_wb_domain;
+struct wb_domain global_wb_domain;
/*
* Length of period for aging writeout fractions of bdis. This is an
@@ -470,9 +468,15 @@
int wb_domain_init(struct wb_domain *dom, gfp_t gfp)
{
memset(dom, 0, sizeof(*dom));
+
+ spin_lock_init(&dom->lock);
+
init_timer_deferrable(&dom->period_timer);
dom->period_timer.function = writeout_period;
dom->period_timer.data = (unsigned long)dom;
+
+ dom->dirty_limit_tstamp = jiffies;
+
return fprop_global_init(&dom->completions, gfp);
}
@@ -532,7 +536,9 @@
static unsigned long hard_dirty_limit(unsigned long thresh)
{
- return max(thresh, global_dirty_limit);
+ struct wb_domain *dom = &global_wb_domain;
+
+ return max(thresh, dom->dirty_limit);
}
/**
@@ -916,17 +922,10 @@
wb->avg_write_bandwidth = avg;
}
-/*
- * The global dirtyable memory and dirty threshold could be suddenly knocked
- * down by a large amount (eg. on the startup of KVM in a swapless system).
- * This may throw the system into deep dirty exceeded state and throttle
- * heavy/light dirtiers alike. To retain good responsiveness, maintain
- * global_dirty_limit for tracking slowly down to the knocked down dirty
- * threshold.
- */
static void update_dirty_limit(unsigned long thresh, unsigned long dirty)
{
- unsigned long limit = global_dirty_limit;
+ struct wb_domain *dom = &global_wb_domain;
+ unsigned long limit = dom->dirty_limit;
/*
* Follow up in one step.
@@ -939,7 +938,7 @@
/*
* Follow down slowly. Use the higher one as the target, because thresh
* may drop below dirty. This is exactly the reason to introduce
- * global_dirty_limit which is guaranteed to lie above the dirty pages.
+ * dom->dirty_limit which is guaranteed to lie above the dirty pages.
*/
thresh = max(thresh, dirty);
if (limit > thresh) {
@@ -948,28 +947,27 @@
}
return;
update:
- global_dirty_limit = limit;
+ dom->dirty_limit = limit;
}
static void global_update_bandwidth(unsigned long thresh,
unsigned long dirty,
unsigned long now)
{
- static DEFINE_SPINLOCK(dirty_lock);
- static unsigned long update_time = INITIAL_JIFFIES;
+ struct wb_domain *dom = &global_wb_domain;
/*
* check locklessly first to optimize away locking for the most time
*/
- if (time_before(now, update_time + BANDWIDTH_INTERVAL))
+ if (time_before(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL))
return;
- spin_lock(&dirty_lock);
- if (time_after_eq(now, update_time + BANDWIDTH_INTERVAL)) {
+ spin_lock(&dom->lock);
+ if (time_after_eq(now, dom->dirty_limit_tstamp + BANDWIDTH_INTERVAL)) {
update_dirty_limit(thresh, dirty);
- update_time = now;
+ dom->dirty_limit_tstamp = now;
}
- spin_unlock(&dirty_lock);
+ spin_unlock(&dom->lock);
}
/*
@@ -1761,10 +1759,12 @@
void writeback_set_ratelimit(void)
{
+ struct wb_domain *dom = &global_wb_domain;
unsigned long background_thresh;
unsigned long dirty_thresh;
+
global_dirty_limits(&background_thresh, &dirty_thresh);
- global_dirty_limit = dirty_thresh;
+ dom->dirty_limit = dirty_thresh;
ratelimit_pages = dirty_thresh / (num_online_cpus() * 32);
if (ratelimit_pages < 16)
ratelimit_pages = 16;