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blk-mq: don't keep offline CPUs mapped to hctx 0 

From commit 4b855ad371 ("blk-mq: Create hctx for each present CPU),
blk-mq doesn't remap queue after CPU topo is changed, that said when
some of these offline CPUs become online, they are still mapped to
hctx 0, then hctx 0 may become the bottleneck of IO dispatch and
completion.

This patch sets up the mapping from the beginning, and aligns to
queue mapping for PCI device (blk_mq_pci_map_queues()).

Cc: Stefan Haberland <sth@linux.vnet.ibm.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: stable@vger.kernel.org
Fixes: 4b855ad371 ("blk-mq: Create hctx for each present CPU)
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
hifive-unleashed-5.1
Ming Lei 2018-04-08 17:48:08 +08:00 committed by Jens Axboe
parent a1c735fb79
commit bffa9909a6
1 changed files with 0 additions and 5 deletions
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5
block/blk-mq-cpumap.c
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@ -16,11 +16,6 @@
static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
{
/*
* Non present CPU will be mapped to queue index 0.
*/
if (!cpu_present(cpu))
return 0;
return cpu % nr_queues;
}