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| author | Uday Shankar <ushankar@purestorage.com> | 2024-04-30 15:16:24 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2024-04-30 15:36:50 -0600 |
| commit | eaf4a9b19b9961f8ca294c39c5f8984a4cf42212 (patch) | |
| tree | fceda50ff687c5afb6028b988fcd3a1afc7f38b0 | |
| parent | 01bc4fda9ea0a6b52f12326486f07a4910666cf6 (diff) | |
| download | linux-eaf4a9b19b9961f8ca294c39c5f8984a4cf42212.tar.gz | |
ublk: remove segment count and size limits
ublk_drv currently creates block devices with the default max_segments
and max_segment_size limits of BLK_MAX_SEGMENTS (128) and
BLK_MAX_SEGMENT_SIZE (65536) respectively. These defaults can
artificially constrain the I/O size seen by the ublk server - for
example, suppose that the ublk server has configured itself to accept
I/Os up to 1M and the application is also issuing 1M sized I/Os. If the
I/O buffer used by the application is backed by 4K pages, the buffer
could consist of up to 1M / 4K = 256 physically discontiguous segments
(even if the buffer is virtually contiguous). As such, the I/O could
exceed the default max_segments limit and get split. This can cause
unnecessary performance issues if the ublk server is optimized to handle
1M I/Os. The block layer's segment count/size limits exist to model
hardware constraints which don't exist in ublk_drv's case, so just
remove those limits for the block devices created by ublk_drv.
Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Riley Thomasson <riley@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20240430211623.2802036-1-ushankar@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/block/ublk_drv.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index bea3d5cf8a834..374e4efa8759f 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -2177,7 +2177,8 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd) .max_hw_sectors = p->max_sectors, .chunk_sectors = p->chunk_sectors, .virt_boundary_mask = p->virt_boundary_mask, - + .max_segments = USHRT_MAX, + .max_segment_size = UINT_MAX, }; struct gendisk *disk; int ret = -EINVAL; |