On Mon, Mar 22, 2021 at 2:27 AM Christian Mauderer
<christian.maude...@embedded-brains.de> wrote:
>
> 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.
> ---
> cpukit/include/rtems/bdbuf.h | 21 ++++
> cpukit/include/rtems/diskdevs.h | 24 ++++-
> cpukit/libblock/src/bdbuf.c | 84 +++++++++++----
> cpukit/libblock/src/blkdev-print-stats.c | 2 +
> testsuites/fstests/fsdosfswrite01/init.c | 3 +
> testsuites/libtests/block14/block14.scn | 19 +++-
> testsuites/libtests/block14/init.c | 124 +++++++++++++++++------
> 7 files changed, 217 insertions(+), 60 deletions(-)
>
> diff --git a/cpukit/include/rtems/bdbuf.h b/cpukit/include/rtems/bdbuf.h
> index fbb4fc05e9..0cde571816 100644
> --- a/cpukit/include/rtems/bdbuf.h
> +++ b/cpukit/include/rtems/bdbuf.h
> @@ -539,6 +539,27 @@ rtems_bdbuf_read (
> rtems_bdbuf_buffer** bd
> );
>
> +/**
missing @brief?
rest of this looks fine on a quick skim
> + * 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
> diff --git a/cpukit/include/rtems/diskdevs.h b/cpukit/include/rtems/diskdevs.h
> index 85d157dcd5..527a8cc955 100644
> --- a/cpukit/include/rtems/diskdevs.h
> +++ b/cpukit/include/rtems/diskdevs.h
> @@ -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.
> */
> diff --git a/cpukit/libblock/src/bdbuf.c b/cpukit/libblock/src/bdbuf.c
> index a7d471507c..8aadf9c8ae 100644
> --- a/cpukit/libblock/src/bdbuf.c
> +++ b/cpukit/libblock/src/bdbuf.c
> @@ -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;
> diff --git a/cpukit/libblock/src/blkdev-print-stats.c
> b/cpukit/libblock/src/blkdev-print-stats.c
> index 8edf24fd8c..539ff08157 100644
> --- a/cpukit/libblock/src/blkdev-print-stats.c
> +++ b/cpukit/libblock/src/blkdev-print-stats.c
> @@ -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,
> diff --git a/testsuites/fstests/fsdosfswrite01/init.c
> b/testsuites/fstests/fsdosfswrite01/init.c
> index e5d8e5d6dd..64b43b7919 100644
> --- a/testsuites/fstests/fsdosfswrite01/init.c
> +++ b/testsuites/fstests/fsdosfswrite01/init.c
> @@ -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,
> diff --git a/testsuites/libtests/block14/block14.scn
> b/testsuites/libtests/block14/block14.scn
> index 7170522579..cf5518adfd 100644
> --- a/testsuites/libtests/block14/block14.scn
> +++ b/testsuites/libtests/block14/block14.scn
> @@ -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 ***
> diff --git a/testsuites/libtests/block14/init.c
> b/testsuites/libtests/block14/init.c
> index b4e73aadc9..13b7ab05ad 100644
> --- a/testsuites/libtests/block14/init.c
> +++ b/testsuites/libtests/block14/init.c
> @@ -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 (action->peek != NULL) {
> + (*action->peek)(dd, action->block, 1);
> + }
>
> - if (sc == RTEMS_SUCCESSFUL) {
> + if (sc == RTEMS_SUCCESSFUL && action->release != NULL) {
> sc = (*action->release)(bd);
> rtems_test_assert(sc == RTEMS_SUCCESSFUL);
> }
> --
> 2.26.2
>
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