Commit b99b00e5 authored by Simon A. F. Lund's avatar Simon A. F. Lund Committed by Tomasz Zawadzki
Browse files

bdev_xnvme: add option to conserve cpu and set default to false 



To achieve the highest possible IO-rates and lowest latency, then CPU
cycles must be spent processing IO. This commit introduces three
different techniques dependendent on the 'io_mechanism' used.

For 'libaio', xNVMe is instructued via 'opts.poll_io' to not wait for
completions, thus xnvme_queue_poke() returns immmediatly, the user can
then call xnvme_queue_poke() as frequently as desired. This requires
xNVMe v0.5.0. Earlier versions will ignore 'opts.poll_io' for 'libaio'.

For 'io_uring', xNVMe is instructed via 'opts.poll_io' to enable
IORING_SETUP_IOPOLL.

For 'io_uring_cmd', xNVMe is instructued via 'opts.poll_sq' to enable
IORING_SETUP_SQPOLL, this sets up a kernel-side thread reaping
completions from user-space on the ring. Note that 'io_uring_cmd'
requires liburing >= 2.2.

This commit enables the above by default. The above can be disabled by
setting 'conserve_cpu' to true on the bdev-setup.

Signed-off-by: default avatarSimon A. F. Lund <simon.lund@samsung.com>
Change-Id: Id54f1e59733ce9ae3b174ad4562904d868d4ef4f
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/14678


Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarJim Harris <james.r.harris@intel.com>
Reviewed-by: default avatarTomasz Zawadzki <tomasz.zawadzki@intel.com>
parent 87757389

doc/jsonrpc.md

+3 −1
Original line number Diff line number Diff line
@@ -5737,6 +5737,7 @@ Name | Optional | Type | Description 
name                    | Required | string      | name of xNVMe bdev to create

filename                | Required | string      | path to device or file (ex: /dev/nvme0n1)

io_mechanism            | Required | string      | IO mechanism to use (ex: libaio, io_uring, io_uring_cmd, etc.)

conserve_cpu            | Optional | boolean     | Whether or not to conserve CPU when polling (default: false)



#### Result
@@ -5754,7 +5755,8 @@ Example request: 
  "params": {

    "name": "bdev_ng0n1",

    "filename": "/dev/ng0n1",

    "io_mechanism": "io_uring_cmd"

    "io_mechanism": "io_uring_cmd",

    "conserve_cpu": false,

  }

}

~~~

module/bdev/xnvme/bdev_xnvme.c

+12 −3
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ struct bdev_xnvme { 
	char			*io_mechanism;

	struct xnvme_dev	*dev;

	uint32_t		nsid;

	bool			conserve_cpu;



	TAILQ_ENTRY(bdev_xnvme) link;

};
@@ -68,6 +69,7 @@ bdev_xnvme_config_json(struct spdk_json_write_ctx *w) 
		spdk_json_write_named_string(w, "name", xnvme->bdev.name);

		spdk_json_write_named_string(w, "filename", xnvme->filename);

		spdk_json_write_named_string(w, "io_mechanism", xnvme->io_mechanism);

		spdk_json_write_named_bool(w, "conserve_cpu", xnvme->conserve_cpu);

		spdk_json_write_object_end(w);



		spdk_json_write_object_end(w);
@@ -304,7 +306,8 @@ bdev_xnvme_queue_destroy_cb(void *io_device, void *ctx_buf) 
}



struct spdk_bdev *

create_xnvme_bdev(const char *name, const char *filename, const char *io_mechanism)

create_xnvme_bdev(const char *name, const char *filename, const char *io_mechanism,

		  bool conserve_cpu)

{

	struct bdev_xnvme *xnvme;

	uint32_t block_size;
@@ -328,9 +331,15 @@ create_xnvme_bdev(const char *name, const char *filename, const char *io_mechani 
		goto error_return;

	}



	if (!strcmp(xnvme->io_mechanism, "io_uring_cmd")) {

	if (!conserve_cpu) {

		if (!strcmp(xnvme->io_mechanism, "libaio")) {

			opts.poll_io = 1;

		} else if (!strcmp(xnvme->io_mechanism, "io_uring")) {

			opts.poll_io = 1;

		} else if (!strcmp(xnvme->io_mechanism, "io_uring_cmd")) {

			opts.poll_sq = 1;

		}

	}



	xnvme->filename = strdup(filename);

	if (!xnvme->filename) {

module/bdev/xnvme/bdev_xnvme.h

+1 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ 
typedef void (*spdk_delete_xnvme_complete)(void *cb_arg, int bdeverrno);



struct spdk_bdev *create_xnvme_bdev(const char *name, const char *filename,

				    const char *io_mechanism);

				    const char *io_mechanism, bool conserve_cpu);



void delete_xnvme_bdev(struct spdk_bdev *bdev, spdk_delete_xnvme_complete cb_fn, void *cb_arg);

module/bdev/xnvme/bdev_xnvme_rpc.c

+3 −1
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ struct rpc_create_xnvme { 
	char *name;

	char *filename;

	char *io_mechanism;

	bool conserve_cpu;

};



/* Free the allocated memory resource after the RPC handling. */
@@ -30,6 +31,7 @@ static const struct spdk_json_object_decoder rpc_create_xnvme_decoders[] = { 
	{"name", offsetof(struct rpc_create_xnvme, name), spdk_json_decode_string},

	{"filename", offsetof(struct rpc_create_xnvme, filename), spdk_json_decode_string},

	{"io_mechanism", offsetof(struct rpc_create_xnvme, io_mechanism), spdk_json_decode_string},

	{"conserve_cpu", offsetof(struct rpc_create_xnvme, conserve_cpu), spdk_json_decode_bool, true},

};



static void
@@ -57,7 +59,7 @@ rpc_bdev_xnvme_create(struct spdk_jsonrpc_request *request, 
		goto cleanup;

	}



	bdev = create_xnvme_bdev(req.name, req.filename, req.io_mechanism);

	bdev = create_xnvme_bdev(req.name, req.filename, req.io_mechanism, req.conserve_cpu);

	if (!bdev) {

		SPDK_ERRLOG("Unable to create xNVMe bdev from file %s\n", req.filename);

		spdk_jsonrpc_send_error_response(request, SPDK_JSONRPC_ERROR_INTERNAL_ERROR,

python/spdk/rpc/bdev.py

+9 −4
Original line number Diff line number Diff line
@@ -492,20 +492,25 @@ def bdev_uring_delete(client, name): 
    return client.call('bdev_uring_delete', params)





def bdev_xnvme_create(client, filename, name, io_mechanism):

def bdev_xnvme_create(client, filename, name, io_mechanism, conserve_cpu=None):

    """Create a bdev with xNVMe backend.



    Args:

        filename: path to device or file (ex: /dev/nvme0n1)

        name: name of xNVMe bdev to create

        io_mechanism: I/O mechanism to use (ex: io_uring, io_uring_cmd, etc.)

        conserve_cpu: Whether or not to conserve CPU when polling (default: False)



    Returns:

        Name of created bdev.

    """

    params = {'name': name,

    params = {

        'name': name,

        'filename': filename,

              'io_mechanism': io_mechanism}

        'io_mechanism': io_mechanism,

    }

    if conserve_cpu:

        params['conserve_cpu'] = conserve_cpu



    return client.call('bdev_xnvme_create', params)