[PATCH 31/49] writeback: implement backing_dev_info->tot_write_bandwidth

Tejun Heo
2015-04-06T20:00:22Z

cgroup writeback support needs to keep track of the sum of
avg_write_bandwidth of all wb's (bdi_writeback's) with dirty inodes to
distribute write workload. This patch adds bdi->tot_write_bandwidth
and updates inode_wb_list_move_locked(), inode_wb_list_del_locked()
and wb_update_write_bandwidth() to adjust it as wb's gain and lose
dirty inodes and its avg_write_bandwidth gets updated.

As the update events are not synchronized with each other,
bdi->tot_write_bandwidth is an atomic_long_t.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
---
fs/fs-writeback.c | 7 ++++++-
include/linux/backing-dev-defs.h | 2 ++
mm/page-writeback.c | 3 +++
3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 29b4f8f..590c3ba 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -87,6 +87,8 @@ static bool wb_io_lists_populated(struct bdi_writeback *wb)
return false;
} else {
set_bit(WB_has_dirty_io, &wb->state);
+ atomic_long_add(wb->avg_write_bandwidth,
+ &wb->bdi->tot_write_bandwidth);
return true;
}
}
@@ -94,8 +96,11 @@ static bool wb_io_lists_populated(struct bdi_writeback *wb)
static void wb_io_lists_depopulated(struct bdi_writeback *wb)
{
if (wb_has_dirty_io(wb) && list_empty(&wb->b_dirty) &&
- list_empty(&wb->b_io) && list_empty(&wb->b_more_io))
+ list_empty(&wb->b_io) && list_empty(&wb->b_more_io)) {
clear_bit(WB_has_dirty_io, &wb->state);
+ atomic_long_sub(wb->avg_write_bandwidth,
+ &wb->bdi->tot_write_bandwidth);
+ }
}

/**
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 7a94b78..d631a61 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -142,6 +142,8 @@ struct backing_dev_info {
unsigned int min_ratio;
unsigned int max_ratio, max_prop_frac;

+ atomic_long_t tot_write_bandwidth; /* sum of active avg_write_bw */
+
struct bdi_writeback wb; /* the root writeback info for this bdi */
struct bdi_writeback_congested wb_congested; /* its congested state */
#ifdef CONFIG_CGROUP_WRITEBACK
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0aa2ffe..26c72e4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -881,6 +881,9 @@ static void wb_update_write_bandwidth(struct bdi_writeback *wb,
avg += (old - avg) >> 3;

out:
+ if (wb_has_dirty_io(wb))
+ atomic_long_add(avg - wb->avg_write_bandwidth,
+ &wb->bdi->tot_write_bandwidth);
wb->write_bandwidth = bw;
wb->avg_write_bandwidth = avg;
}
--
2.1.0