On 2/5/18 8:20 AM, Ming Lei wrote: > Quite a few HBAs(such as HPSA, megaraid, mpt3sas, ..) support multiple > reply queues, but tags is often HBA wide. > > These HBAs have switched to use pci_alloc_irq_vectors(PCI_IRQ_AFFINITY) > for automatic affinity assignment. > > Now 84676c1f21e8ff5(genirq/affinity: assign vectors to all possible CPUs) > has been merged to V4.16-rc, and it is easy to allocate all offline CPUs > for some irq vectors, this can't be avoided even though the allocation > is improved. > > So all these drivers have to avoid to ask HBA to complete request in > reply queue which hasn't online CPUs assigned, and HPSA has been broken > with v4.15+: > > https://marc.info/?l=linux-kernel&m=151748144730409&w=2 > > This issue can be solved generically and easily via blk_mq(scsi_mq) multiple > hw queue by mapping each reply queue into hctx, but one tricky thing is > the HBA wide(instead of hw queue wide) tags. > > This patch is based on the following Hannes's patch: > > https://marc.info/?l=linux-block&m=149132580511346&w=2 > > One big difference with Hannes's is that this patch only makes the tags sbitmap > and active_queues data structure HBA wide, and others are kept as NUMA locality, > such as request, hctx, tags, ... > > The following patch will support global tags on null_blk, also the performance > data is provided, no obvious performance loss is observed when the whole > hw queue depth is same. GLOBAL implies that it's, strangely enough, global. That isn't really the case. Why not call this BLK_MQ_F_HOST_TAGS or something like that? I'd welcome better names, but global doesn't seem to be a great choice. BLK_MQ_F_SET_TAGS? -- Jens Axboe
