| Message ID | CAHsXFKFy+ZVvaCr=H224VGA755k45fAJhz5TaMz+tOP6hNpj1g@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] add io_uring support in scsi layer | expand |
On 9/3/20 10:14 AM, Kashyap Desai wrote: > Currently io_uring support is only available in the block layer. > This RFC is to extend support of mq_poll in the scsi layer. I think this needs to clarify that io_uring with IOPOLL is not currently supported, outside of that everything else should work and no extra support in the driver is needed. The summary and title makes it sound like it currently doesn't work at all, which obviously isn't true! > megaraid_sas and mpt3sas driver will be immediate users of this interface. > Both the drivers can use mq_poll only if it has exposed more than one > nr_hw_queues. > Waiting for below changes to enable shared host tag support. Just a quick question, do these low level drivers support non-irq mode for requests? That's a requirement for IOPOLL support to work well, and I don't think it'd be worthwhile to plumb anything up that _doesn't_ support pure non-IRQ mode. That's identical to the NVMe support, we will not allow IOPOLL if you don't have explicit non-IRQ support. Outside of that, no comments on this enablement patch, looks pretty straight forward and fine to me.
> On 9/3/20 10:14 AM, Kashyap Desai wrote: > > Currently io_uring support is only available in the block layer. > > This RFC is to extend support of mq_poll in the scsi layer. > > I think this needs to clarify that io_uring with IOPOLL is not currently > supported, outside of that everything else should work and no extra > support > in the driver is needed. > > The summary and title makes it sound like it currently doesn't work at > all, > which obviously isn't true! I actually mean io_uring with IOPOLL support. I will fix this. > > > megaraid_sas and mpt3sas driver will be immediate users of this > > interface. > > Both the drivers can use mq_poll only if it has exposed more than one > > nr_hw_queues. > > Waiting for below changes to enable shared host tag support. > > Just a quick question, do these low level drivers support non-irq mode for > requests? That's a requirement for IOPOLL support to work well, and I > don't > think it'd be worthwhile to plumb anything up that _doesn't_ support pure > non-IRQ mode. That's identical to the NVMe support, we will not allow > IOPOLL if you don't have explicit non-IRQ support. I guess you mean non-IRQ mode = There will not be any msix vector associated for poll_queues and h/w can still work in this mode. If above is correct, yes both the controller can support non-IRQ mode, but we need support of shared host tag as well for completeness of this feature in driver. Both the h/w are single submission queue and multiple reply queue, but using shared host tagset support we will enable simulated multiple hw queue. I have megaraid_sas driver patch available and it does identical to what NVME driver does. Driver allocates some extra reply queues and it will be marked as poll_queue. This poll_queue will not have associated msix vectors. All the IO completion on this queue will be done from IOPOLL interface. I tested megaraid_sas driver having 8 poll_queues and using io_uring hiprio=1 settings. It can reach 3.2M IOPs and there is *zero* interrupt. This is what NVME does so I assume this is what you wanted to confirm here. > > Outside of that, no comments on this enablement patch, looks pretty > straight > forward and fine to me. Thanks for review. > > -- > Jens Axboe
> > megaraid_sas and mpt3sas driver will be immediate users of this > > interface. > > Both the drivers can use mq_poll only if it has exposed more than one > > nr_hw_queues. > > Perhaps you could add some comments in scsi_host.h about what the > int (* mq_poll)(struct Scsi_Host *shost, unsigned int queue_num); > > callback should do. And you could implement it in the scsi_debug driver > which > should have all the other hooks as it is part 15 of the shared host tag > support > patchset. I will add supporting comment in scsi_host.h. I will also add scsi_debug support and include it in my next patchset. Kashyap > > > Waiting for below changes to enable shared host tag support. > > > > https://patchwork.kernel.org/cover/11724429/ > > I'm testing this at the moment. So far so good. > > Doug Gilbert
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 780cf084e366..7a3c59d2dfcc 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1802,6 +1802,19 @@ static void scsi_mq_exit_request(struct blk_mq_tag_set *set, struct request *rq, cmd->sense_buffer); } + +static int scsi_mq_poll(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + struct scsi_device *sdev = q->queuedata; + struct Scsi_Host *shost = sdev->host; + + if (shost->hostt->mq_poll) + return shost->hostt->mq_poll(shost, hctx->queue_num); + + return 0; +} + static int scsi_map_queues(struct blk_mq_tag_set *set) { struct Scsi_Host *shost = container_of(set, struct Scsi_Host, tag_set); @@ -1869,6 +1882,7 @@ static const struct blk_mq_ops scsi_mq_ops_no_commit = { .cleanup_rq = scsi_cleanup_rq, .busy = scsi_mq_lld_busy, .map_queues = scsi_map_queues, + .poll = scsi_mq_poll, }; @@ -1897,6 +1911,7 @@ static const struct blk_mq_ops scsi_mq_ops = { .cleanup_rq = scsi_cleanup_rq, .busy = scsi_mq_lld_busy, .map_queues = scsi_map_queues, + .poll = scsi_mq_poll, }; struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev) @@ -1929,6 +1944,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) else tag_set->ops = &scsi_mq_ops_no_commit; tag_set->nr_hw_queues = shost->nr_hw_queues ? : 1; + tag_set->nr_maps = shost->nr_maps ? : 1; tag_set->queue_depth = shost->can_queue; tag_set->cmd_size = cmd_size; tag_set->numa_node = NUMA_NO_NODE; diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h index e76bac4d14c5..5844374a85b1 100644 --- a/include/scsi/scsi_cmnd.h +++ b/include/scsi/scsi_cmnd.h @@ -9,6 +9,7 @@ #include <linux/types.h> #include <linux/timer.h> #include <linux/scatterlist.h> +#include <scsi/scsi_host.h> #include <scsi/scsi_device.h> #include <scsi/scsi_request.h> diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index 701f178b20ae..d34602c68d0b 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -269,6 +269,8 @@ struct scsi_host_template { * Status: OPTIONAL */ int (* map_queues)(struct Scsi_Host *shost); + + int (* mq_poll)(struct Scsi_Host *shost, unsigned int queue_num); /* * Check if scatterlists need to be padded for DMA draining. @@ -610,6 +612,7 @@ struct Scsi_Host { * the total queue depth is can_queue. */ unsigned nr_hw_queues; + unsigned nr_maps; unsigned active_mode:2; unsigned unchecked_isa_dma:1;
Currently io_uring support is only available in the block layer. This RFC is to extend support of mq_poll in the scsi layer. megaraid_sas and mpt3sas driver will be immediate users of this interface. Both the drivers can use mq_poll only if it has exposed more than one nr_hw_queues. Waiting for below changes to enable shared host tag support. https://patchwork.kernel.org/cover/11724429/ Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com> --- drivers/scsi/scsi_lib.c | 16 ++++++++++++++++ include/scsi/scsi_cmnd.h | 1 + include/scsi/scsi_host.h | 3 +++ 3 files changed, 20 insertions(+)