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NVMe: Set queue max segments

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This sets the queue's max segment size to match the device's
capabilities. The default of 128 is usable until a device's transfer
capability exceeds 512k, assuming a device page size of 4k. Many nvme
devices exceed that transfer limit, so this lets the block layer know what
kind of commands it to allow to form rather than unnecessarily split them.

One additional segment is added to account for a transfer that may start
in the middle of a page.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Keith Busch 2015-08-12 16:17:54 -06:00 committed by Jens Axboe
parent 22d109c1bb
commit e824410ffc
1 changed files with 4 additions and 1 deletions
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5
drivers/block/nvme-core.c
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@ -2120,8 +2120,11 @@ static void nvme_alloc_ns(struct nvme_dev *dev, unsigned nsid)
list_add_tail(&ns->list, &dev->namespaces);
blk_queue_logical_block_size(ns->queue, 1 << ns->lba_shift);
if (dev->max_hw_sectors)
if (dev->max_hw_sectors) {
blk_queue_max_hw_sectors(ns->queue, dev->max_hw_sectors);
blk_queue_max_segments(ns->queue,
((dev->max_hw_sectors << 9) / dev->page_size) + 1);
}
if (dev->stripe_size)
blk_queue_chunk_sectors(ns->queue, dev->stripe_size >> 9);
if (dev->vwc & NVME_CTRL_VWC_PRESENT)