diff options
Diffstat (limited to 'src/H5FDmpio.c')
| -rw-r--r-- | src/H5FDmpio.c | 97 |
1 files changed, 74 insertions, 23 deletions
diff --git a/src/H5FDmpio.c b/src/H5FDmpio.c index 0801b17..a898786 100644 --- a/src/H5FDmpio.c +++ b/src/H5FDmpio.c @@ -1060,7 +1060,7 @@ done: fprintf(stdout, "Leaving H5FD_mpio_open\n" ); #endif FUNC_LEAVE_NOAPI(ret_value) -} +} /* end H5FD_mpio_open() */ /*------------------------------------------------------------------------- @@ -1892,10 +1892,9 @@ H5FD_mpio_flush(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, hbool_t closing) HDassert(H5FD_MPIO == file->pub.driver_id); /* Only sync the file if we are not going to immediately close it */ - if(!closing) { + if(!closing) if(MPI_SUCCESS != (mpi_code = MPI_File_sync(file->f))) HMPI_GOTO_ERROR(FAIL, "MPI_File_sync failed", mpi_code) - } /* end if */ done: #ifdef H5FDmpio_DEBUG @@ -1912,12 +1911,33 @@ done: * * Purpose: Make certain the file's size matches it's allocated size * + * This is a little sticky in the mpio case, as it is not + * easy for us to track the current EOF by extracting it from + * write calls. + * + * Instead, we first check to see if the eoa has changed since + * the last call to this function. If it has, we call + * MPI_File_get_size() to determine the current EOF, and + * only call MPI_File_set_size() if this value disagrees + * with the current eoa. + * * Return: Success: Non-negative * Failure: Negative * * Programmer: Quincey Koziol * January 31, 2008 * + * Changes: Heavily reworked to avoid unnecessary MPI_File_set_size() + * calls. The hope is that these calls are superfluous in the + * typical case, allowing us to avoid truncates most of the + * time. + * + * The basic idea is to query the file system to get the + * current eof, and only truncate if the file systems + * conception of the eof disagrees with our eoa. + * + * JRM -- 10/27/17 + * *------------------------------------------------------------------------- */ static herr_t @@ -1935,29 +1955,60 @@ H5FD_mpio_truncate(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, hbool_t H5_ATTR_ HDassert(file); HDassert(H5FD_MPIO == file->pub.driver_id); - /* Extend the file to make sure it's large enough, then sync. - * Unfortunately, keeping track of EOF is an expensive operation, so - * we can't just check whether EOF<EOA like with other drivers. - * Therefore we'll just read the byte at EOA-1 and then write it back. */ - if(file->eoa > file->last_eoa) { - int mpi_code; /* mpi return code */ - MPI_Offset mpi_off; + if(!H5F_addr_eq(file->eoa, file->last_eoa)) { + int mpi_code; /* mpi return code */ + MPI_Offset size; + MPI_Offset needed_eof; + + /* In principle, it is possible for the size returned by the + * call to MPI_File_get_size() to depend on whether writes from + * all proceeses have completed at the time process 0 makes the + * call. + * + * In practice, most (all?) truncate calls will come after a barrier + * and with no interviening writes to the file (with the possible + * exception of sueprblock / superblock extension message updates). + * + * Check the "MPI file closing" flag in the API context to determine + * if we can skip the barrier. + */ + if(!H5CX_get_mpi_file_flushing()) + if(MPI_SUCCESS != (mpi_code = MPI_Barrier(file->comm))) + HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code) - if(H5FD_mpi_haddr_to_MPIOff(file->eoa, &mpi_off) < 0) - HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "cannot convert from haddr_t to MPI_Offset") + /* Only processor p0 will get the filesize and broadcast it. */ + /* (Note that throwing an error here will cause non-rank 0 processes + * to hang in following Bcast. -QAK, 3/17/2018) + */ + if(0 == file->mpi_rank) + if(MPI_SUCCESS != (mpi_code = MPI_File_get_size(file->f, &size))) + HMPI_GOTO_ERROR(FAIL, "MPI_File_get_size failed", mpi_code) - /* Extend the file's size */ - if(MPI_SUCCESS != (mpi_code = MPI_File_set_size(file->f, mpi_off))) - HMPI_GOTO_ERROR(FAIL, "MPI_File_set_size failed", mpi_code) + /* Broadcast file size */ + if(MPI_SUCCESS != (mpi_code = MPI_Bcast(&size, (int)sizeof(MPI_Offset), MPI_BYTE, 0, file->comm))) + HMPI_GOTO_ERROR(FAIL, "MPI_Bcast failed", mpi_code) - /* Don't let any proc return until all have extended the file. - * (Prevents race condition where some processes go ahead and write - * more data to the file before all the processes have finished making - * it the shorter length, potentially truncating the file and dropping - * the new data written) - */ - if(MPI_SUCCESS != (mpi_code = MPI_Barrier(file->comm))) - HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code) + if(H5FD_mpi_haddr_to_MPIOff(file->eoa, &needed_eof) < 0) + HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "cannot convert from haddr_t to MPI_Offset") + + /* eoa != eof. Set eof to eoa */ + if(size != needed_eof) { + /* Extend the file's size */ + if(MPI_SUCCESS != (mpi_code = MPI_File_set_size(file->f, needed_eof))) + HMPI_GOTO_ERROR(FAIL, "MPI_File_set_size failed", mpi_code) + + /* In general, we must wait until all processes have finished + * the truncate before any process can continue, since it is + * possible that a process would write at the end of the + * file, and this write would be discarded by the truncate. + * + * While this is an issue for a user initiated flush, it may + * not be an issue at file close. If so, we may be able to + * optimize out the following barrier in that case. + */ + if(MPI_SUCCESS != (mpi_code = MPI_Barrier(file->comm))) + HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code) + } /* end if */ /* Update the 'last' eoa value */ file->last_eoa = file->eoa; |