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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> |
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| .. | ||
| aoe | ||
| drbd | ||
| mtip32xx | ||
| null_blk | ||
| rnbd | ||
| xen-blkback | ||
| zram | ||
| amiflop.c | ||
| ataflop.c | ||
| brd.c | ||
| floppy.c | ||
| Kconfig | ||
| loop.c | ||
| Makefile | ||
| n64cart.c | ||
| nbd.c | ||
| pktcdvd.c | ||
| ps3disk.c | ||
| ps3vram.c | ||
| rbd_types.h | ||
| rbd.c | ||
| sunvdc.c | ||
| swim3.c | ||
| swim_asm.S | ||
| swim.c | ||
| ublk_drv.c | ||
| virtio_blk.c | ||
| xen-blkfront.c | ||
| z2ram.c | ||