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libblock: Add rtems_bdbuf_peek()

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Adds a peek function that allows (for example) a file system to suggest
the next blocks that should be used for read ahead. This can increase
the read speed of fragmented files.

Update #3689
This commit is contained in:
Christian Mauderer
2021-01-19 15:33:35 +01:00
parent 62bbb0cc46
commit 6ae79e6df6
7 changed files with 219 additions and 60 deletions
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23
cpukit/include/rtems/bdbuf.h
View File

@@ -539,6 +539,29 @@ rtems_bdbuf_read (
rtems_bdbuf_buffer** bd
);
/**
* @brief Give a hint which blocks should be cached next.
*
* Provide a hint to the read ahead mechanism which blocks should be cached
* next. This overwrites the default linear pattern. You should use it in (for
* example) a file system to tell bdbuf where the next part of a fragmented file
* is. If you know the length of the file, you can provide that too.
*
* Before you can use this function, the rtems_bdbuf_init() routine must be
* called at least once to initialize everything. Otherwise you might get
* unexpected results.
*
* @param dd [in] The disk device.
* @param block [in] Linear media block number.
* @param nr_blocks [in] Number of consecutive blocks that can be pre-fetched.
*/
void
rtems_bdbuf_peek (
rtems_disk_device *dd,
rtems_blkdev_bnum block,
uint32_t nr_blocks
);
/**
* Release the buffer obtained by a read call back to the cache. If the buffer
* was obtained by a get call and was not already in the cache the release

24
cpukit/include/rtems/diskdevs.h
View File

@@ -58,6 +58,11 @@ typedef int (*rtems_block_device_ioctl)(
*/
#define RTEMS_DISK_READ_AHEAD_NO_TRIGGER ((rtems_blkdev_bnum) -1)
/**
* @brief Size value to set number of blocks based on config and disk size.
*/
#define RTEMS_DISK_READ_AHEAD_SIZE_AUTO (0)
/**
* @brief Block device read-ahead control.
*/
@@ -71,7 +76,8 @@ typedef struct {
* @brief Block value to trigger the read-ahead request.
*
* A value of @ref RTEMS_DISK_READ_AHEAD_NO_TRIGGER will disable further
* read-ahead requests since no valid block can have this value.
* read-ahead requests (except the ones triggered by @a rtems_bdbuf_peek)
* since no valid block can have this value.
*/
rtems_blkdev_bnum trigger;
@@ -82,6 +88,14 @@ typedef struct {
* be arbitrary.
*/
rtems_blkdev_bnum next;
/**
* @brief Size of the next read-ahead request in blocks.
*
* A value of @ref RTEMS_DISK_READ_AHEAD_SIZE_AUTO will try to read the rest
* of the disk but at most the configured max_read_ahead_blocks.
*/
uint32_t nr_blocks;
} rtems_blkdev_read_ahead;
/**
@@ -110,10 +124,16 @@ typedef struct {
/**
* @brief Read-ahead transfer count.
*
* Each read-ahead transfer may read multiple blocks.
* Each read-ahead transfer may read multiple blocks. This counts all
* transfers (including peeks).
*/
uint32_t read_ahead_transfers;
/**
* @brief Read-ahead transfers caused by a peek.
*/
uint32_t read_ahead_peeks;
/**
* @brief Count of blocks transfered from the device.
*/

84
cpukit/libblock/src/bdbuf.c
View File

@@ -2018,6 +2018,23 @@ rtems_bdbuf_read_ahead_reset (rtems_disk_device *dd)
dd->read_ahead.trigger = RTEMS_DISK_READ_AHEAD_NO_TRIGGER;
}
static void
rtems_bdbuf_read_ahead_add_to_chain (rtems_disk_device *dd)
{
rtems_status_code sc;
rtems_chain_control *chain = &bdbuf_cache.read_ahead_chain;
if (rtems_chain_is_empty (chain))
{
sc = rtems_event_send (bdbuf_cache.read_ahead_task,
RTEMS_BDBUF_READ_AHEAD_WAKE_UP);
if (sc != RTEMS_SUCCESSFUL)
rtems_bdbuf_fatal (RTEMS_BDBUF_FATAL_RA_WAKE_UP);
}
rtems_chain_append_unprotected (chain, &dd->read_ahead.node);
}
static void
rtems_bdbuf_check_read_ahead_trigger (rtems_disk_device *dd,
rtems_blkdev_bnum block)
@@ -2026,18 +2043,8 @@ rtems_bdbuf_check_read_ahead_trigger (rtems_disk_device *dd,
&& dd->read_ahead.trigger == block
&& !rtems_bdbuf_is_read_ahead_active (dd))
{
rtems_status_code sc;
rtems_chain_control *chain = &bdbuf_cache.read_ahead_chain;
if (rtems_chain_is_empty (chain))
{
sc = rtems_event_send (bdbuf_cache.read_ahead_task,
RTEMS_BDBUF_READ_AHEAD_WAKE_UP);
if (sc != RTEMS_SUCCESSFUL)
rtems_bdbuf_fatal (RTEMS_BDBUF_FATAL_RA_WAKE_UP);
}
rtems_chain_append_unprotected (chain, &dd->read_ahead.node);
dd->read_ahead.nr_blocks = RTEMS_DISK_READ_AHEAD_SIZE_AUTO;
rtems_bdbuf_read_ahead_add_to_chain(dd);
}
}
@@ -2112,6 +2119,24 @@ rtems_bdbuf_read (rtems_disk_device *dd,
return sc;
}
void
rtems_bdbuf_peek (rtems_disk_device *dd,
rtems_blkdev_bnum block,
uint32_t nr_blocks)
{
rtems_bdbuf_lock_cache ();
if (bdbuf_cache.read_ahead_enabled && nr_blocks > 0)
{
rtems_bdbuf_read_ahead_reset(dd);
dd->read_ahead.next = block;
dd->read_ahead.nr_blocks = nr_blocks;
rtems_bdbuf_read_ahead_add_to_chain(dd);
}
rtems_bdbuf_unlock_cache ();
}
static rtems_status_code
rtems_bdbuf_check_bd_and_lock_cache (rtems_bdbuf_buffer *bd, const char *kind)
{
@@ -2952,18 +2977,33 @@ rtems_bdbuf_read_ahead_task (rtems_task_argument arg)
if (bd != NULL)
{
uint32_t transfer_count = dd->block_count - block;
uint32_t transfer_count = dd->read_ahead.nr_blocks;
uint32_t blocks_until_end_of_disk = dd->block_count - block;
uint32_t max_transfer_count = bdbuf_config.max_read_ahead_blocks;
if (transfer_count >= max_transfer_count)
{
transfer_count = max_transfer_count;
dd->read_ahead.trigger = block + transfer_count / 2;
dd->read_ahead.next = block + transfer_count;
}
else
{
dd->read_ahead.trigger = RTEMS_DISK_READ_AHEAD_NO_TRIGGER;
if (transfer_count == RTEMS_DISK_READ_AHEAD_SIZE_AUTO) {
transfer_count = blocks_until_end_of_disk;
if (transfer_count >= max_transfer_count)
{
transfer_count = max_transfer_count;
dd->read_ahead.trigger = block + transfer_count / 2;
dd->read_ahead.next = block + transfer_count;
}
else
{
dd->read_ahead.trigger = RTEMS_DISK_READ_AHEAD_NO_TRIGGER;
}
} else {
if (transfer_count > blocks_until_end_of_disk) {
transfer_count = blocks_until_end_of_disk;
}
if (transfer_count > max_transfer_count) {
transfer_count = max_transfer_count;
}
++dd->stats.read_ahead_peeks;
}
++dd->stats.read_ahead_transfers;

2
cpukit/libblock/src/blkdev-print-stats.c
View File

@@ -47,6 +47,7 @@ void rtems_blkdev_print_stats(
" READ HITS | %" PRIu32 "\n"
" READ MISSES | %" PRIu32 "\n"
" READ AHEAD TRANSFERS | %" PRIu32 "\n"
" READ AHEAD PEEKS | %" PRIu32 "\n"
" READ BLOCKS | %" PRIu32 "\n"
" READ ERRORS | %" PRIu32 "\n"
" WRITE TRANSFERS | %" PRIu32 "\n"
@@ -59,6 +60,7 @@ void rtems_blkdev_print_stats(
stats->read_hits,
stats->read_misses,
stats->read_ahead_transfers,
stats->read_ahead_peeks,
stats->read_blocks,
stats->read_errors,
stats->write_transfers,

3
testsuites/fstests/fsdosfswrite01/init.c
View File

@@ -129,6 +129,7 @@ static void test_normal_file_write(
.read_hits = 0,
.read_misses = 0,
.read_ahead_transfers = 0,
.read_ahead_peeks = 0,
.read_blocks = 0,
.read_errors = 0,
.write_transfers = 1,
@@ -139,6 +140,7 @@ static void test_normal_file_write(
.read_hits = 3,
.read_misses = 2,
.read_ahead_transfers = 0,
.read_ahead_peeks = 0,
.read_blocks = 2,
.read_errors = 0,
.write_transfers = 1,
@@ -149,6 +151,7 @@ static void test_normal_file_write(
.read_hits = 3,
.read_misses = 3,
.read_ahead_transfers = 0,
.read_ahead_peeks = 0,
.read_blocks = 3,
.read_errors = 0,
.write_transfers = 1,

19
testsuites/libtests/block14/block14.scn
View File

@@ -6,19 +6,30 @@ action 3
action 4
action 5
action 6
action 7
action 8
action 9
action 10
action 11
action 12
action 13
action 14
action 15
-------------------------------------------------------------------------------
DEVICE STATISTICS
----------------------+--------------------------------------------------------
MEDIA BLOCK SIZE | 0
MEDIA BLOCK COUNT | 1
BLOCK SIZE | 2
READ HITS | 2
READ MISSES | 3
READ AHEAD TRANSFERS | 2
READ BLOCKS | 5
READ HITS | 4
READ MISSES | 7
READ AHEAD TRANSFERS | 6
READ AHEAD PEEKS | 3
READ BLOCKS | 13
READ ERRORS | 1
WRITE TRANSFERS | 2
WRITE BLOCKS | 2
WRITE ERRORS | 1
----------------------+--------------------------------------------------------
*** END OF TEST BLOCK 14 ***

124
testsuites/libtests/block14/init.c
View File

@@ -29,9 +29,9 @@
const char rtems_test_name[] = "BLOCK 14";
#define ACTION_COUNT 7
#define ACTION_COUNT 16
#define BLOCK_COUNT 6
#define BLOCK_COUNT 14
#define DISK_PATH "/disk"
@@ -42,50 +42,104 @@ typedef struct {
rtems_blkdev_bnum block,
rtems_bdbuf_buffer **bd_ptr
);
void (*peek)(
rtems_disk_device *dd,
rtems_blkdev_bnum block,
uint32_t nr_blocks
);
rtems_status_code expected_get_status;
rtems_status_code (*release)(rtems_bdbuf_buffer *bd);
} test_action;
static const test_action actions [ACTION_COUNT] = {
{ 0, rtems_bdbuf_read, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 1, rtems_bdbuf_read, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 2, rtems_bdbuf_read, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 0, rtems_bdbuf_read, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 4, rtems_bdbuf_get, RTEMS_SUCCESSFUL, rtems_bdbuf_sync },
{ 5, rtems_bdbuf_read, RTEMS_IO_ERROR, rtems_bdbuf_release },
{ 5, rtems_bdbuf_get, RTEMS_SUCCESSFUL, rtems_bdbuf_sync }
/* normal read ahead */
{ 0, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 1, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 2, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
/* re-read a cached block */
{ 0, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
/* cause some writes */
{ 4, rtems_bdbuf_get, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_sync },
{ 5, rtems_bdbuf_read, NULL, RTEMS_IO_ERROR, rtems_bdbuf_release },
{ 5, rtems_bdbuf_get, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_sync },
/* interrupt normal read ahead with a peek */
{ 9, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 13, NULL, rtems_bdbuf_peek, 0, NULL },
{ 10, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 11, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
{ 12, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
/* peek with hit */
{ 6, NULL, rtems_bdbuf_peek, 0, NULL },
{ 6, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
/* (wrong) peek with reading different block */
{ 8, NULL, rtems_bdbuf_peek, 0, NULL },
{ 7, rtems_bdbuf_read, NULL, RTEMS_SUCCESSFUL, rtems_bdbuf_release },
};
#define STATS(a, b, c, d, e, f, g, h) \
#define STATS(a, b, c, d, e, f, g, h, i) \
{ \
.read_hits = a, \
.read_misses = b, \
.read_ahead_transfers = c, \
.read_blocks = d, \
.read_errors = e, \
.write_transfers = f, \
.write_blocks = g, \
.write_errors = h \
.read_ahead_peeks = d, \
.read_blocks = e, \
.read_errors = f, \
.write_transfers = g, \
.write_blocks = h, \
.write_errors = i \
}
static const rtems_blkdev_stats expected_stats [ACTION_COUNT] = {
STATS(0, 1, 0, 1, 0, 0, 0, 0),
STATS(0, 2, 1, 3, 0, 0, 0, 0),
STATS(1, 2, 2, 4, 0, 0, 0, 0),
STATS(2, 2, 2, 4, 0, 0, 0, 0),
STATS(2, 2, 2, 4, 0, 1, 1, 0),
STATS(2, 3, 2, 5, 1, 1, 1, 0),
STATS(2, 3, 2, 5, 1, 2, 2, 1)
STATS(0, 1, 0, 0, 1, 0, 0, 0, 0),
STATS(0, 2, 1, 0, 3, 0, 0, 0, 0),
STATS(1, 2, 2, 0, 4, 0, 0, 0, 0),
STATS(2, 2, 2, 0, 4, 0, 0, 0, 0),
STATS(2, 2, 2, 0, 4, 0, 1, 1, 0),
STATS(2, 3, 2, 0, 5, 1, 1, 1, 0),
STATS(2, 3, 2, 0, 5, 1, 2, 2, 1),
STATS(2, 4, 2, 0, 6, 1, 2, 2, 1),
STATS(2, 4, 3, 1, 7, 1, 2, 2, 1),
STATS(2, 5, 3, 1, 8, 1, 2, 2, 1),
STATS(2, 6, 4, 1, 10, 1, 2, 2, 1),
STATS(3, 6, 4, 1, 10, 1, 2, 2, 1),
STATS(3, 6, 5, 2, 11, 1, 2, 2, 1),
STATS(4, 6, 5, 2, 11, 1, 2, 2, 1),
STATS(4, 6, 6, 3, 12, 1, 2, 2, 1),
STATS(4, 7, 6, 3, 13, 1, 2, 2, 1),
};
static const int expected_block_access_counts [ACTION_COUNT] [BLOCK_COUNT] = {
{ 1, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 0, 0, 0 },
{ 1, 1, 1, 1, 0, 0 },
{ 1, 1, 1, 1, 0, 0 },
{ 1, 1, 1, 1, 1, 0 },
{ 1, 1, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 2 }
{ 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 1, 2, 0, 0, 0, 1, 0, 0, 0, 0 },
{ 1, 1, 1, 1, 1, 2, 0, 0, 0, 1, 0, 0, 0, 1 },
{ 1, 1, 1, 1, 1, 2, 0, 0, 0, 1, 1, 0, 0, 1 },
{ 1, 1, 1, 1, 1, 2, 0, 0, 0, 1, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 2, 0, 0, 0, 1, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 2, 1, 0, 0, 1, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 2, 1, 0, 0, 1, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 2, 1, 0, 1, 1, 1, 1, 1, 1 },
{ 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1 },
};
static int block_access_counts [BLOCK_COUNT];
@@ -132,10 +186,16 @@ static void test_actions(rtems_disk_device *dd)
printf("action %i\n", i);
sc = (*action->get)(dd, action->block, &bd);
rtems_test_assert(sc == action->expected_get_status);
if (action->get != NULL) {
sc = (*action->get)(dd, action->block, &bd);
rtems_test_assert(sc == action->expected_get_status);
}
if (sc == RTEMS_SUCCESSFUL) {
if (action->peek != NULL) {
(*action->peek)(dd, action->block, 1);
}
if (sc == RTEMS_SUCCESSFUL && action->release != NULL) {
sc = (*action->release)(bd);
rtems_test_assert(sc == RTEMS_SUCCESSFUL);
}