This introduces a percentage-flushing mechanism that works in-tandem to the delay timer. The percentage argument is based on the number of chunks dirty. It was chosen to use number of chunks due to large drives requiring smaller and smaller percentages (eg, 32TB drives-> 1% is 320GB). The first patch fixes a performance gap observed in RAID1 configurations. With a synchronous qd1 workload, bitmap writes can easily become almost half of the I/O. This could be argued to be expected, but undesirable. Moving the unplug operation to the periodic delay work seemed to help the situation. The second part of this set adds a new field in the superblock and version, allowing for a new argument through mdadm specifying the number of chunks allowed to be dirty before flushing. Accompanying this set is an RFC for mdadm patch. It lacks documentation which will be sent in v2 if this changeset is appropriate. Jonathan Derrick (2): md/bitmap: Move unplug to daemon thread md/bitmap: Add chunk-count-based bitmap flushing drivers/md/md-bitmap.c | 38 +++++++++++++++++++++++++++++++++++--- drivers/md/md-bitmap.h | 5 ++++- drivers/md/md.h | 1 + drivers/md/raid1.c | 2 -- drivers/md/raid10.c | 4 ---- 5 files changed, 40 insertions(+), 10 deletions(-) -- 2.31.1
