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21d2287119
Metadata I/Os are scheduled to minimize their impact on user data I/Os. When there are enough LUNs instantiated (i.e., enough bandwidth), it is easy to interleave metadata and data one after the other so that metadata I/Os are the ones being blocked and not vice-versa. We do this by calculating the distance between the I/Os in terms of the LUNs that are not in used, and selecting a free LUN that satisfies a the simple heuristic that metadata is scheduled behind. The per-LUN semaphores guarantee consistency. This works fine on >1 LUN configuration. However, when a single LUN is instantiated, this design leads to a deadlock, where metadata waits to be scheduled on a free LUN. This patch implements the 1 LUN case by simply scheduling the metadada I/O after the data I/O. In the process, we refactor the way a line is replaced to ensure that metadata writes are submitted after data writes in order to guarantee block sequentiality. Note that, since there is only one LUN, both I/Os will block each other by design. However, such configuration only pursues tight read latencies, not write bandwidth. Signed-off-by: Javier González <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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| .. | ||
| core.c | ||
| Kconfig | ||
| Makefile | ||
| pblk-cache.c | ||
| pblk-core.c | ||
| pblk-gc.c | ||
| pblk-init.c | ||
| pblk-map.c | ||
| pblk-rb.c | ||
| pblk-read.c | ||
| pblk-recovery.c | ||
| pblk-rl.c | ||
| pblk-sysfs.c | ||
| pblk-write.c | ||
| pblk.h | ||
| rrpc.c | ||
| rrpc.h | ||