diff options
| -rw-r--r-- | cpukit/sapi/include/confdefs.h | 14 | ||||
| -rw-r--r-- | doc/user/conf.t | 55 | ||||
| -rw-r--r-- | testsuites/psxtests/psximfs02/init.c | 4 |
3 files changed, 71 insertions, 2 deletions
diff --git a/cpukit/sapi/include/confdefs.h b/cpukit/sapi/include/confdefs.h index 8115a85724..e29111638a 100644 --- a/cpukit/sapi/include/confdefs.h +++ b/cpukit/sapi/include/confdefs.h @@ -3820,5 +3820,19 @@ const rtems_libio_helper rtems_fs_init_helper = #endif #endif +/* + * IMFS block size for in memory files (memfiles) must be a power of + * two between 16 and 512 inclusive. + */ +#if ((CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK != 16) && \ + (CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK != 32) && \ + (CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK != 64) && \ + (CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK != 128) && \ + (CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK != 256) && \ + (CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK != 512)) + #error "IMFS Memfile block size must be a power of 2 between 16 and 512" +#endif + + #endif /* end of include file */ diff --git a/doc/user/conf.t b/doc/user/conf.t index b19dbd9e82..b77250ff24 100644 --- a/doc/user/conf.t +++ b/doc/user/conf.t @@ -2749,6 +2749,61 @@ options will be defined as well @end itemize @c +@c === CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK === +@c +@subsection Specify Block Size for IMFS + +@findex CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK + +@table @b +@item CONSTANT: +@code{CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK} + +@item DATA TYPE: +Boolean feature macro. + +@item RANGE: +Valid values for this configuration parameter are a power of two (2) +between 16 and 512 inclusive. In other words, valid values are 16, +32, 64, 128, 256,and 512. + +@item DEFAULT VALUE: +The default IMFS block size is 128 bytes. + +@end table + +@subheading DESCRIPTION: +This configuration parameter specifies the block size for in-memory files +managed by the IMFS. The configured block size has two impacts. The first +is the average amount of unused memory in the last block of each file. For +example, when the block size is 512, on average one-half of the last block +of each file will remain unused and the memory is wasted. In contrast, +when the block size is 16, the average unused memory per file is only +8 bytes. However, it requires more allocations for the same size file +and thus more overhead per block for the dynamic memory management. + +Second, the block size has an impact on the maximum size file that can +be stored in the IMFS. With smaller block size, the maximum file size +is correspondingly smaller. The following shows the maximum file size +possible based on the configured block size: + +@itemize @bullet +@item when the block size is 16 bytes, the maximum file size is 1,328 +bytes. +@item when the block size is 32 bytes, the maximum file size is 18,656 +bytes. +@item when the block size is 64 bytes, the maximum file size is 279,488 +bytes. +@item when the block size is 128 bytes, the maximum file size is +4,329,344 bytes. +@item when the block size is 256 bytes, the maximum file size is +68,173,568 bytes. +@item when the block size is 512 bytes, the maximum file size is +1,082,195,456 bytes. +@end itemize + + +@c @c === CONFIGURE_IMFS_DISABLE_CHOWN === @c @subsection Disable Change Owner Support of Root IMFS diff --git a/testsuites/psxtests/psximfs02/init.c b/testsuites/psxtests/psximfs02/init.c index d372a6f11b..2a55d08f38 100644 --- a/testsuites/psxtests/psximfs02/init.c +++ b/testsuites/psxtests/psximfs02/init.c @@ -1,5 +1,5 @@ /* - * COPYRIGHT (c) 1989-2014. + * COPYRIGHT (c) 1989-2015. * On-Line Applications Research Corporation (OAR). * * The license and distribution terms for this file may be @@ -211,7 +211,7 @@ rtems_task Init( #define CONFIGURE_FILESYSTEM_IMFS #define CONFIGURE_MAXIMUM_TASKS 1 -#define CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK 15 +#define CONFIGURE_IMFS_MEMFILE_BYTES_PER_BLOCK 16 #define CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS 4 #define CONFIGURE_INITIAL_EXTENSIONS RTEMS_TEST_INITIAL_EXTENSION |