[PATCH 1/1] blk-mq: map all HWQ also in hyperthreaded system

[Guilherme G. Piccoli]

On 06/28/2017 09:44 AM, Max Gurtovoy wrote:
> This patch performs sequential mapping between CPUs and queues.
> In case the system has more CPUs than HWQs then there are still
> CPUs to map to HWQs. In hyperthreaded system, map the unmapped CPUs
> and their siblings to the same HWQ.
> This actually fixes a bug that found unmapped HWQs in a system with
> 2 sockets, 18 cores per socket, 2 threads per core (total 72 CPUs)
> running NVMEoF (opens upto maximum of 64 HWQs).
> 
> Performance results running fio (72 jobs, 128 iodepth)
> using null_blk (w/w.o patch):
> 
> bs      IOPS(read submit_queues=72)   IOPS(write submit_queues=72)   IOPS(read submit_queues=24)  IOPS(write submit_queues=24)
> -----  ----------------------------  ------------------------------ ---------------------------- -----------------------------
> 512    4890.4K/4723.5K                 4524.7K/4324.2K                   4280.2K/4264.3K               3902.4K/3909.5K
> 1k     4910.1K/4715.2K                 4535.8K/4309.6K                   4296.7K/4269.1K               3906.8K/3914.9K
> 2k     4906.3K/4739.7K                 4526.7K/4330.6K                   4301.1K/4262.4K               3890.8K/3900.1K
> 4k     4918.6K/4730.7K                 4556.1K/4343.6K                   4297.6K/4264.5K               3886.9K/3893.9K
> 8k     4906.4K/4748.9K                 4550.9K/4346.7K                   4283.2K/4268.8K               3863.4K/3858.2K
> 16k    4903.8K/4782.6K                 4501.5K/4233.9K                   4292.3K/4282.3K               3773.1K/3773.5K
> 32k    4885.8K/4782.4K                 4365.9K/4184.2K                   4307.5K/4289.4K               3780.3K/3687.3K
> 64k    4822.5K/4762.7K                 2752.8K/2675.1K                   4308.8K/4312.3K               2651.5K/2655.7K
> 128k   2388.5K/2313.8K                 1391.9K/1375.7K                   2142.8K/2152.2K               1395.5K/1374.2K
> 

Max, thanks for this patch. I was having the same issue, and was
thinking in how to address...

Your patch fixes it for me, just tested it.
I can test any follow-up patch you send, basaed on reviews you got in
the list.

Cheers,


Guilherme