spu_create - create a new spu context
Standard C library (
libc,
-lc)
#include <sys/spu.h> /* Definition of SPU_* constants */
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
int syscall(SYS_spu_create, const char *pathname, unsigned int flags,
mode_t mode, int neighbor_fd);
Note: glibc provides no wrapper for
spu_create(), necessitating
the use of
syscall(2).
The
spu_create() system call is used on PowerPC machines that implement
the Cell Broadband Engine Architecture in order to access Synergistic
Processor Units (SPUs). It creates a new logical context for an SPU in
pathname and returns a file descriptor associated with it.
pathname must refer to a nonexistent directory in the mount point of
the SPU filesystem (
spufs). If
spu_create() is successful, a
directory is created at
pathname and it is populated with the files
described in
spufs(7).
When a context is created, the returned file descriptor can only be passed to
spu_run(2), used as the
dirfd argument to the
*at family
of system calls (e.g.,
openat(2)), or closed; other operations are not
defined. A logical SPU context is destroyed (along with all files created
within the context's
pathname directory) once the last reference to the
context has gone; this usually occurs when the file descriptor returned by
spu_create() is closed.
The
mode argument (minus any bits set in the process's
umask(2))
specifies the permissions used for creating the new directory in
spufs.
See
stat(2) for a full list of the possible
mode values.
The
neighbor_fd is used only when the
SPU_CREATE_AFFINITY_SPU flag
is specified; see below.
The
flags argument can be zero or any bitwise OR-ed combination of the
following constants:
- SPU_CREATE_EVENTS_ENABLED
- Rather than using signals for reporting DMA errors, use the
event argument to spu_run(2).
- SPU_CREATE_GANG
- Create an SPU gang instead of a context. (A gang is a group
of SPU contexts that are functionally related to each other and which
share common scheduling parameters—priority and policy. In the
future, gang scheduling may be implemented causing the group to be
switched in and out as a single unit.)
- A new directory will be created at the location specified
by the pathname argument. This gang may be used to hold other SPU
contexts, by providing a pathname that is within the gang directory to
further calls to spu_create().
- SPU_CREATE_NOSCHED
- Create a context that is not affected by the SPU scheduler.
Once the context is run, it will not be scheduled out until it is
destroyed by the creating process.
- Because the context cannot be removed from the SPU, some
functionality is disabled for SPU_CREATE_NOSCHED contexts. Only a
subset of the files will be available in this context directory in
spufs. Additionally, SPU_CREATE_NOSCHED contexts cannot dump
a core file when crashing.
- Creating SPU_CREATE_NOSCHED contexts requires the
CAP_SYS_NICE capability.
- SPU_CREATE_ISOLATE
- Create an isolated SPU context. Isolated contexts are
protected from some PPE (PowerPC Processing Element) operations, such as
access to the SPU local store and the NPC register.
- Creating SPU_CREATE_ISOLATE contexts also requires
the SPU_CREATE_NOSCHED flag.
-
SPU_CREATE_AFFINITY_SPU (since Linux 2.6.23)
- Create a context with affinity to another SPU context. This
affinity information is used within the SPU scheduling algorithm. Using
this flag requires that a file descriptor referring to the other SPU
context be passed in the neighbor_fd argument.
-
SPU_CREATE_AFFINITY_MEM (since Linux 2.6.23)
- Create a context with affinity to system memory. This
affinity information is used within the SPU scheduling algorithm.
On success,
spu_create() returns a new file descriptor. On failure, -1 is
returned, and
errno is set to indicate the error.
- EACCES
- The current user does not have write access to the
spufs(7) mount point.
- EEXIST
- An SPU context already exists at the given pathname.
- EFAULT
-
pathname is not a valid string pointer in the
calling process's address space.
- EINVAL
-
pathname is not a directory in the spufs(7)
mount point, or invalid flags have been provided.
- ELOOP
- Too many symbolic links were found while resolving
pathname.
- EMFILE
- The per-process limit on the number of open file
descriptors has been reached.
- ENAMETOOLONG
-
pathname is too long.
- ENFILE
- The system-wide limit on the total number of open files has
been reached.
- ENODEV
- An isolated context was requested, but the hardware does
not support SPU isolation.
- ENOENT
- Part of pathname could not be resolved.
- ENOMEM
- The kernel could not allocate all resources required.
- ENOSPC
- There are not enough SPU resources available to create a
new context or the user-specific limit for the number of SPU contexts has
been reached.
- ENOSYS
- The functionality is not provided by the current system,
because either the hardware does not provide SPUs or the spufs module is
not loaded.
- ENOTDIR
- A part of pathname is not a directory.
- EPERM
- The SPU_CREATE_NOSCHED flag has been given, but the
user does not have the CAP_SYS_NICE capability.
pathname must point to a location beneath the mount point of
spufs. By convention, it gets mounted in
/spu.
The
spu_create() system call was added in Linux 2.6.16.
This call is Linux-specific and implemented only on the PowerPC architecture.
Programs using this system call are not portable.
spu_create() is meant to be used from libraries that implement a more
abstract interface to SPUs, not to be used from regular applications. See
http://www.bsc.es/projects/deepcomputing/linuxoncell/
for the recommended libraries.
Prior to the addition of the
SPU_CREATE_AFFINITY_SPU flag in Linux
2.6.23, the
spu_create() system call took only three arguments (i.e.,
there was no
neighbor_fd argument).
See
spu_run(2) for an example of the use of
spu_create()
close(2),
spu_run(2),
capabilities(7),
spufs(7)