Ubuntu Manpage: spu_create - create a new spu context

NAME

       spu_create - create a new spu context

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #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).

DESCRIPTION

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.

RETURN VALUE

       On  success,  spu_create() returns a new file descriptor.  On failure, -1 is returned, and
       errno is set to indicate the error.

ERRORS

       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.

FILES

       pathname must point to a location beneath the mount point of  spufs.   By  convention,  it
       gets mounted in /spu.

STANDARDS

       Linux on PowerPC.

HISTORY

       Linux 2.6.16.

       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).

NOTES

       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.

EXAMPLES

       See spu_run(2) for an example of the use of spu_create()