From 21d2287119e843929c29fb1adbd271bde1fac7ae Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Javier=20Gonz=C3=A1lez?= Date: Fri, 13 Oct 2017 14:46:26 +0200 Subject: lightnvm: pblk: enable 1 LUN configuration MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Matias Bjørling Signed-off-by: Jens Axboe --- drivers/lightnvm/pblk-init.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/lightnvm/pblk-init.c') diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c index 34527646c01b..3c3749186053 100644 --- a/drivers/lightnvm/pblk-init.c +++ b/drivers/lightnvm/pblk-init.c @@ -711,8 +711,12 @@ add_emeta_page: } lm->emeta_bb = geo->nr_luns - i; - lm->min_blk_line = 1 + DIV_ROUND_UP(lm->smeta_sec + lm->emeta_sec[0], - geo->sec_per_blk); + + lm->min_blk_line = 1; + if (geo->nr_luns > 1) + lm->min_blk_line += DIV_ROUND_UP(lm->smeta_sec + + lm->emeta_sec[0], geo->sec_per_blk); + if (lm->min_blk_line > lm->blk_per_line) { pr_err("pblk: config. not supported. Min. LUN in line:%d\n", lm->blk_per_line); -- cgit v1.2.3