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()