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Commit 766a9d6e authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

writeback: implement backing_dev_info->tot_write_bandwidth 



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: default avatarTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent d6c10f1f

fs/fs-writeback.c

+6 −1
Original line number Diff line number Diff line
@@ -99,6 +99,8 @@ 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;

	}

}
@@ -106,8 +108,11 @@ 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);

	}

}



/**

include/linux/backing-dev-defs.h

+2 −0
Original line number Diff line number Diff line
@@ -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

mm/page-writeback.c

+3 −0
Original line number Diff line number Diff line
@@ -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;

}