625 lines
17 KiB
Groff
625 lines
17 KiB
Groff
.\" $NetBSD: dmover.9,v 1.10 2005/12/24 21:27:22 perry Exp $
|
|
.\"
|
|
.\" Copyright (c) 2002 Wasabi Systems, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Written by Jason R. Thorpe for Wasabi Systems, Inc.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed for the NetBSD Project by
|
|
.\" Wasabi Systems, Inc.
|
|
.\" 4. The name of Wasabi Systems, Inc. may not be used to endorse
|
|
.\" or promote products derived from this software without specific prior
|
|
.\" written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd December 24, 2005
|
|
.Dt DMOVER 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm dmover_backend_register ,
|
|
.Nm dmover_backend_unregister ,
|
|
.Nm dmover_session_create ,
|
|
.Nm dmover_session_destroy ,
|
|
.Nm dmover_request_alloc ,
|
|
.Nm dmover_request_free ,
|
|
.Nm dmover_process ,
|
|
.Nm dmover_done
|
|
.Nd hardware-assisted data mover interface
|
|
.Sh SYNOPSIS
|
|
.In dev/dmover/dmovervar.h
|
|
.Pp
|
|
Client interface routines:
|
|
.Pp
|
|
.Ft int
|
|
.Fn "dmover_session_create" "const char *" "struct dmover_session **"
|
|
.Ft void
|
|
.Fn "dmover_session_destroy" "struct dmover_session *"
|
|
.Ft "struct dmover_request *"
|
|
.Fn "dmover_request_alloc" "struct dmover_session *" "dmover_buffer *"
|
|
.Ft void
|
|
.Fn "dmover_request_free" "struct dmover_request *"
|
|
.Ft void
|
|
.Fn "dmover_process" "struct dmover_request *"
|
|
.Pp
|
|
Back-end interface routines:
|
|
.Pp
|
|
.Ft void
|
|
.Fn "dmover_backend_register" "struct dmover_backend *"
|
|
.Ft void
|
|
.Fn "dmover_backend_unregister" "struct dmover_backend *"
|
|
.Ft void
|
|
.Fn "dmover_done" "struct dmover_request *"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm dmover
|
|
facility provides an interface to hardware-assisted data movers.
|
|
This can be used to copy data from one location in memory to another, clear
|
|
a region of memory, fill a region of memory with a pattern, and perform
|
|
simple operations on multiple regions of memory, such as an XOR, without
|
|
intervention by the CPU.
|
|
.Pp
|
|
The drivers for hardware-assisted data movers present themselves to
|
|
.Nm dmover
|
|
by registering their capabilities.
|
|
When a client wishes to use a
|
|
.Nm dmover
|
|
function, it creates a session for that function, which identifies back-ends
|
|
capable of performing that function.
|
|
The client then enqueues requests on that session, which the back-ends
|
|
process asynchronously.
|
|
The client may choose to block until the request is completed, or may
|
|
have a call-back invoked once the request has been completed.
|
|
.Pp
|
|
When a client creates a session, the
|
|
.Nm dmover
|
|
facility identifies back-ends which are capable of handling the requested
|
|
function.
|
|
When a request is scheduled for processing, the
|
|
.Nm dmover
|
|
scheduler will identify the best back-end to process the request from
|
|
the list of candidate back-ends, in an effort to provide load balancing,
|
|
while considering the relative performance of each back-end.
|
|
.Pp
|
|
A
|
|
.Nm dmover
|
|
function always has one output region.
|
|
A function may have zero or more input regions, or may use an immediate
|
|
value as an input.
|
|
For functions which use input regions, the lengths of each input region
|
|
and the output region must be the same.
|
|
All
|
|
.Nm dmover
|
|
functions with the same name will have the same number of and type inputs.
|
|
If a back-end attempts to register a function which violates this invariant,
|
|
behavior is undefined.
|
|
.Pp
|
|
The
|
|
.Nm dmover
|
|
facility supports several types of buffer descriptors.
|
|
For functions which use input regions, each input buffer descriptor and
|
|
the output buffer descriptor must be of the same type.
|
|
This restriction may be removed in a future revision of the interface.
|
|
.Pp
|
|
The
|
|
.Nm dmover
|
|
facility may need to interrupt request processing and restart it.
|
|
Clients of the
|
|
.Nm dmover
|
|
facility should take care to avoid unwanted side-effects should this occur.
|
|
In particular, for functions which use input regions, no input region may
|
|
overlap with the output region.
|
|
.Ss DATA STRUCTURES
|
|
The
|
|
.Nm dmover
|
|
facility shares several data structures between the client and
|
|
back-end in order to describe sessions and requests.
|
|
.Bd -literal -offset indent
|
|
typedef enum {
|
|
DMOVER_BUF_LINEAR,
|
|
DMOVER_BUF_UIO
|
|
} dmover_buffer_type;
|
|
|
|
typedef struct {
|
|
void *l_addr;
|
|
size_t l_len;
|
|
} dmover_buf_linear;
|
|
|
|
typedef union {
|
|
dmover_buf_linear dmbuf_linear;
|
|
struct uio *dmbuf_uio;
|
|
} dmover_buffer;
|
|
.Ed
|
|
.Pp
|
|
Together, these data types are used to describe buffer data structures
|
|
which the
|
|
.Nm dmover
|
|
facility understands.
|
|
Additional buffer types may be added in future revisions of the
|
|
.Nm dmover
|
|
interface.
|
|
.Pp
|
|
The
|
|
.Fa dmover_assignment
|
|
structure contains the information about the back-end to which a
|
|
request is currently assigned.
|
|
It contains the following public members:
|
|
.Bl -tag -width "XXXX"
|
|
.It struct dmover_backend *das_backend
|
|
This is a pointer to the back-end.
|
|
.It const struct dmover_algdesc *das_algdesc
|
|
This is a pointer to the algorithm description provided by
|
|
the back-end for the request's function.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fa dmover_session
|
|
structure contains the following public members:
|
|
.Bl -tag -width "XXXX"
|
|
.It void *dses_cookie
|
|
This is a pointer to client private data.
|
|
.It int dses_ninputs
|
|
This is the number of inputs used by the selected function.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fa dmover_request
|
|
structure contains the following public members:
|
|
.Bl -tag -width "XXXX"
|
|
.It TAILQ_ENTRY(dmover_request) dreq_dmbq
|
|
Linkage on the back-end's queue of pending requests.
|
|
.It struct dmover_session *dreq_session
|
|
Pointer to the session with which this request is associated.
|
|
This is intended for use by the back-end.
|
|
.It struct dmover_assignment *dreq_assignment
|
|
Pointer to the
|
|
.Fa dmover_assignment
|
|
structure which describes the back-end to which the request is
|
|
currently assigned.
|
|
The back-end is assigned when the request is scheduled with
|
|
.Fn dmover_process .
|
|
.It void (*dreq_callback)(struct dmover_request *)
|
|
This is a pointer to an optional call-back function provided by the
|
|
client.
|
|
If provided, the call-back is invoked when the request is complete.
|
|
This field must be
|
|
.Dv NULL
|
|
if
|
|
.Em DMOVER_REQ_WAIT
|
|
is set in
|
|
.Em dreq_flags .
|
|
.It void *dreq_cookie
|
|
This is a pointer to client private data specific to the request.
|
|
.It void *dreq_dmbcookie
|
|
This is a pointer to back-end private data, for use while the back-end
|
|
is actively processing a request.
|
|
.It volatile int dreq_flags
|
|
The following flags are defined:
|
|
.Bl -tag -width "DMOVER_REQ_RUNNINGXX"
|
|
.It DMOVER_REQ_DONE
|
|
The request has been completed.
|
|
If not using a call-back, the client may poll this bit to determine
|
|
if a request has been processed.
|
|
.It DMOVER_REQ_ERROR
|
|
An error has occurred while processing the request.
|
|
.It DMOVER_REQ_RUNNING
|
|
The request is currently being executed by the back-end.
|
|
Once a command is running, it cannot be cancelled, and must run to completion.
|
|
.It DMOVER_REQ_WAIT
|
|
If set by the client,
|
|
.Fn dmover_process
|
|
will wait for the request to complete using
|
|
.Xr tsleep 9 .
|
|
This flag may only be used if the caller has a valid thread context.
|
|
If this flag is set, a callback may not be used.
|
|
.El
|
|
.It int dreq_error
|
|
If the
|
|
.Em DMOVER_REQ_ERROR
|
|
bit is set, this contains the
|
|
.Xr errno 2
|
|
value indicating the error that occurred during processing.
|
|
.It dmover_buffer_type dreq_outbuf_type
|
|
The type of the output buffer.
|
|
.It dmover_buffer dreq_outbuf
|
|
The output buffer.
|
|
.It uint8_t dreq_immediate[8]
|
|
This is the input for algorithms which use an immediate value.
|
|
Values smaller than 8 bytes should use the least-significant bytes first.
|
|
For example, a 32-bit integer would occupy bytes 0, 1, 2, and 3.
|
|
.It dmover_buffer_type dreq_inbuf_type
|
|
The type of the input buffer.
|
|
This is only used if the
|
|
.Nm dmover
|
|
function has one or more inputs.
|
|
.It dmover_buffer *dreq_inbuf
|
|
A pointer to an array of input buffers.
|
|
This is only used if the
|
|
.Nm dmover
|
|
function has one or more inputs.
|
|
The number of inputs, and thus the number of valid elements in the
|
|
array, is specified by the algorithm description for the session.
|
|
.El
|
|
.Ss CLIENT INTERFACE
|
|
The following functions are provided to the client:
|
|
.Bl -tag -width "XXXX"
|
|
.It int Fn dmover_session_create "const char *function" \
|
|
"struct dmover_session **sessionp"
|
|
.Pp
|
|
The
|
|
.Fn dmover_session_create
|
|
function creates a data mover session for the specified data movement
|
|
function
|
|
.Fa function .
|
|
A handle to the new session is returned in
|
|
.Fa *sessionp .
|
|
.Pp
|
|
The following are valid data movement function names:
|
|
.Bl -tag -width "fill8xx"
|
|
.It Dq zero
|
|
Fill a memory region with zeros.
|
|
This algorithm has an input count of 0.
|
|
.It Dq fill8
|
|
Fill a memory region with an 8-bit pattern.
|
|
This algorithm has an input count of 0.
|
|
The pattern is provided in the
|
|
.Em dreq_imm8
|
|
member of the
|
|
.Fa dmover_request
|
|
structure.
|
|
.It Dq copy
|
|
Copy a memory region from one location to another.
|
|
This algorithm has an input count of 1.
|
|
.It Dq xor2
|
|
Perform an XOR operation on 2 inputs.
|
|
This algorithm has an input count of 2.
|
|
.It Dq xor3
|
|
Perform an XOR operation on 3 inputs.
|
|
This algorithm has an input count of 3.
|
|
.It Dq xor4
|
|
Perform an XOR operation on 4 inputs.
|
|
This algorithm has an input count of 4.
|
|
.It Dq xor5
|
|
Perform an XOR operation on 5 inputs.
|
|
This algorithm has an input count of 5.
|
|
.It Dq xor6
|
|
Perform an XOR operation on 6 inputs.
|
|
This algorithm has an input count of 6.
|
|
.It Dq xor7
|
|
Perform an XOR operation on 7 inputs.
|
|
This algorithm has an input count of 7.
|
|
.It Dq xor8
|
|
Perform an XOR operation on 8 inputs.
|
|
This algorithm has an input count of 8.
|
|
.El
|
|
.Pp
|
|
Users of the
|
|
.Nm dmover
|
|
facility are encouraged to use the following aliases for the well-known
|
|
function names, as doing so saves space and reduces the chance of programming
|
|
errors:
|
|
.Bl -tag -width "DMOVER_FUNC_FILL32xx"
|
|
.It DMOVER_FUNC_ZERO
|
|
.Dq zero
|
|
.Pq Va dmover_funcname_zero
|
|
.It DMOVER_FUNC_FILL8
|
|
.Dq fill8
|
|
.Pq Va dmover_funcname_fill8
|
|
.It DMOVER_FUNC_COPY
|
|
.Dq copy
|
|
.Pq Va dmover_funcname_copy
|
|
.It DMOVER_FUNC_XOR2
|
|
.Dq xor2
|
|
.Pq Va dmover_funcname_xor2
|
|
.It DMOVER_FUNC_XOR3
|
|
.Dq xor3
|
|
.Pq Va dmover_funcname_xor3
|
|
.It DMOVER_FUNC_XOR4
|
|
.Dq xor4
|
|
.Pq Va dmover_funcname_xor4
|
|
.It DMOVER_FUNC_XOR5
|
|
.Dq xor5
|
|
.Pq Va dmover_funcname_xor5
|
|
.It DMOVER_FUNC_XOR6
|
|
.Dq xor6
|
|
.Pq Va dmover_funcname_xor6
|
|
.It DMOVER_FUNC_XOR7
|
|
.Dq xor7
|
|
.Pq Va dmover_funcname_xor7
|
|
.It DMOVER_FUNC_XOR8
|
|
.Dq xor8
|
|
.Pq Va dmover_funcname_xor8
|
|
.El
|
|
.It void Fn dmover_session_destroy "struct dmover_session *session"
|
|
.Pp
|
|
The
|
|
.Fn dmover_session_destroy
|
|
function tears down a data mover session and releases all resources
|
|
associated with it.
|
|
.It struct dmover_request * Fn dmover_request_alloc \
|
|
"struct dmover_session *session" "dmover_buffer *inbuf"
|
|
.Pp
|
|
The
|
|
.Fn dmover_request_alloc
|
|
function allocates a
|
|
.Nm dmover
|
|
request structure and associates it with the specified session.
|
|
If the
|
|
.Fa inbuf
|
|
argument is not
|
|
.Dv NULL ,
|
|
.Fa inbuf
|
|
is used as the array of input buffer descriptors in the request.
|
|
Otherwise, if
|
|
.Fa inbuf
|
|
is
|
|
.Dv NULL
|
|
and the
|
|
.Nm dmover
|
|
function requires input buffers, the input buffer descriptors will be
|
|
allocated automatically using
|
|
.Xr malloc 9 .
|
|
.Pp
|
|
If the request structure or input buffer descriptors cannot be allocated,
|
|
.Fn dmover_request_alloc
|
|
return
|
|
.Dv NULL
|
|
to indicate failure.
|
|
.It void Fn dmover_request_free "struct dmover_request *req"
|
|
.Pp
|
|
The
|
|
.Fn dmover_request_free
|
|
function frees a
|
|
.Nm dmover
|
|
request structure.
|
|
If the
|
|
.Nm dmover
|
|
function requires input buffers, and the input buffer descriptors
|
|
associated with
|
|
.Fa req
|
|
were allocated by
|
|
.Fn dmover_request_alloc ,
|
|
then the input buffer descriptors will also be freed.
|
|
.It void Fn dmover_process "struct dmover_request *req"
|
|
.Pp
|
|
The
|
|
.Fn dmover_process
|
|
function submits the
|
|
.Nm dmover
|
|
request
|
|
.Fa req
|
|
for processing.
|
|
The call-back specified by the request is invoked when processing is
|
|
complete.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn dmover_session_create
|
|
and
|
|
.Fn dmover_session_destroy
|
|
functions must not be called from interrupt context.
|
|
.Pp
|
|
The
|
|
.Fn dmover_request_alloc ,
|
|
.Fn dmover_request_free ,
|
|
and
|
|
.Fn dmover_process
|
|
functions may be called from interrupt handlers at levels
|
|
.Em IPL_BIO ,
|
|
.Em IPL_SOFTCLOCK ,
|
|
and
|
|
.Em IPL_SOFTNET ,
|
|
or in non-interrupt context.
|
|
.Pp
|
|
The request completion call-back is called from a software interrupt
|
|
handler at
|
|
.Em IPL_SOFTCLOCK .
|
|
.Ss BACK-END INTERFACE
|
|
A back-end describes the
|
|
.Nm dmover
|
|
functions it can perform using an array of
|
|
.Fa dmover_algdesc
|
|
structures:
|
|
.Bd -literal -offset indent
|
|
struct dmover_algdesc {
|
|
const char *dad_name; /* algorithm name */
|
|
void *dad_data; /* opaque algorithm description */
|
|
int dad_ninputs; /* number of inputs */
|
|
};
|
|
.Ed
|
|
.Pp
|
|
The
|
|
.Em dad_name
|
|
member points to a valid
|
|
.Nm dmover
|
|
function name which the client may specify.
|
|
The
|
|
.Em dad_data
|
|
member points to a back-end-specific description of the algorithm.
|
|
.Pp
|
|
A back-end presents itself to the
|
|
.Nm dmover
|
|
facility using the
|
|
.Fa dmover_backend
|
|
structure.
|
|
The back-end must initialize the following members of the structure:
|
|
.Bl -tag -width "XXXX"
|
|
.It const char *dmb_name
|
|
This is the name of the back-end.
|
|
.It u_int dmb_speed
|
|
This is an estimate of the number of kilobytes/second that the
|
|
back-end can process.
|
|
.It void *dmb_cookie
|
|
This is a pointer to back-end private data.
|
|
.It const struct dmover_algdesc *dmb_algdescs
|
|
This points to an array of
|
|
.Fa dmover_algdesc
|
|
structures which describe the functions the data mover can perform.
|
|
.It int dmb_nalgdescs
|
|
This is the number of elements in the
|
|
.Em dmb_algdescs
|
|
array.
|
|
.It void (*dmb_process)(struct dmover_backend *)
|
|
This is the entry point to the back-end used to process requests.
|
|
.El
|
|
.Pp
|
|
When invoked by the
|
|
.Nm dmover
|
|
facility, the back-end's
|
|
.Fn (*dmb_process)
|
|
function should examine the pending request queue in its
|
|
.Fa dmover_backend
|
|
structure:
|
|
.Bl -tag -width "XXXX"
|
|
.It TAILQ_HEAD(, dmover_request) dmb_pendreqs
|
|
This is the queue of pending requests.
|
|
.It int dmb_npendreqs
|
|
This is the number of requests in the
|
|
.Em dmb_pendreqs
|
|
queue.
|
|
.El
|
|
.Pp
|
|
If an error occurs when processing the request, the
|
|
.Em DMOVER_REQ_ERROR
|
|
bit must be set in the
|
|
.Em dreq_flags
|
|
member of the request, and the
|
|
.Em dreq_error
|
|
member set to an
|
|
.Xr errno 2
|
|
value to indicate the error.
|
|
.Pp
|
|
When the back-end has finished processing the request, it must call
|
|
the
|
|
.Fn dmover_done
|
|
function.
|
|
This function eventually invokes the client's call-back routine.
|
|
.Pp
|
|
If a hardware-assisted data mover uses interrupts, the interrupt handlers
|
|
should be registered at IPL_BIO.
|
|
.Pp
|
|
The following functions are provided to the back-ends:
|
|
.Bl -tag -width "XXXX"
|
|
.It void Fn dmover_backend_register "struct dmover_backend *backend"
|
|
.Pp
|
|
The
|
|
.Fn dmover_backend_register
|
|
function registers the back-end
|
|
.Fa backend
|
|
with the
|
|
.Nm dmover
|
|
facility.
|
|
.It void Fn dmover_backend_unregister "struct dmover_backend *backend"
|
|
.Pp
|
|
The
|
|
.Fn dmover_backend_unregister
|
|
function removes the back-end
|
|
.Fa backend
|
|
from the
|
|
.Nm dmover
|
|
facility.
|
|
The back-end must already be registered.
|
|
.It void Fn dmover_done "struct dmover_request *req"
|
|
.Pp
|
|
The
|
|
.Fn dmover_done
|
|
function is called by the back-end when it has finished processing
|
|
a request, whether the request completed successfully or not.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn dmover_backend_register
|
|
and
|
|
.Fn dmover_backend_unregister
|
|
functions must not be called from interrupt context.
|
|
.Pp
|
|
The
|
|
.Fn dmover_done
|
|
function may be called at
|
|
.Em IPL_BIO ,
|
|
.Em IPL_SOFTCLOCK ,
|
|
.Em IPL_SOFTNET ,
|
|
or in non-interrupt context.
|
|
.Sh EXAMPLES
|
|
The following is an example of a client using
|
|
.Nm dmover
|
|
to zero-fill a region of memory.
|
|
In this example, the CPU will be able to context switch to another
|
|
thread and perform work while the hardware-assisted data mover clears
|
|
the specified block of memory.
|
|
.Bd -literal
|
|
int
|
|
hw_bzero(void *buf, size_t len)
|
|
{
|
|
struct dmover_session *dses;
|
|
struct dmover_request *dreq;
|
|
int error;
|
|
|
|
error = dmover_session_create(DMOVER_FUNC_ZERO, &dses);
|
|
if (error)
|
|
return (error);
|
|
|
|
dreq = dmover_request_alloc(dses, NULL);
|
|
if (dreq == NULL) {
|
|
dmover_session_destroy(dses);
|
|
return (ENOMEM);
|
|
}
|
|
|
|
dreq->dreq_flags = DMOVER_REQ_WAIT;
|
|
dreq->dreq_callback = NULL;
|
|
dreq->dreq_outbuf.dreq_outbuf_type = DMOVER_BUF_LINEAR;
|
|
dreq->dreq_outbuf.dmbuf_linear.l_addr = buf;
|
|
dreq->dreq_outbuf.dmbuf_linear.l_len = len;
|
|
|
|
dmover_process(dreq);
|
|
|
|
error = (dreq->dreq_flags & DMOVER_REQ_ERROR) ?
|
|
dreq->dreq_error : 0;
|
|
|
|
dmover_request_free(dreq);
|
|
dmover_session_destroy(dses);
|
|
|
|
return (error);
|
|
}
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr queue 3 ,
|
|
.Xr dmoverio 4
|
|
.Sh HISTORY
|
|
The
|
|
.Nm dmover
|
|
facility first appeared in
|
|
.Nx 2.0 .
|
|
.Sh AUTHORS
|
|
The
|
|
.Nm dmover
|
|
facility was designed and implemented by
|
|
.An Jason R. Thorpe
|
|
.Aq thorpej@wasabisystems.com
|
|
and contributed by Wasabi Systems, Inc.
|
|
.Sh BUGS
|
|
The mechanism by which a back-end should advertise its performance to
|
|
the request scheduler is not well-defined.
|
|
Therefore, the load-balancing mechanism within the request scheduler is
|
|
also not well-defined.
|