예제 #1
0
void
buf_read_ibuf_merge_pages(
/*======================*/
	ibool	sync,		/* in: TRUE if the caller wants this function
				to wait for the highest address page to get
				read in, before this function returns */
	ulint*	space_ids,	/* in: array of space ids */
	ib_longlong* space_versions,/* in: the spaces must have this version
				number (timestamp), otherwise we discard the
				read; we use this to cancel reads if
				DISCARD + IMPORT may have changed the
				tablespace size */
	ulint*	page_nos,	/* in: array of page numbers to read, with the
				highest page number the last in the array */
	ulint	n_stored)	/* in: number of page numbers in the array */
{
	ulint	err;
	ulint	i;

	ut_ad(!ibuf_inside());
#ifdef UNIV_IBUF_DEBUG
	ut_a(n_stored < UNIV_PAGE_SIZE);
#endif
	while (buf_pool->n_pend_reads
	       > buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
		os_thread_sleep(500000);
	}

	for (i = 0; i < n_stored; i++) {
		buf_read_page_low(&err,
				  (i + 1 == n_stored) && sync,
				  BUF_READ_ANY_PAGE,
				  space_ids[i], space_versions[i],
				  page_nos[i]);

		if (err == DB_TABLESPACE_DELETED) {
			/* We have deleted or are deleting the single-table
			tablespace: remove the entries for that page */

			ibuf_merge_or_delete_for_page(NULL, space_ids[i],
						      page_nos[i], FALSE);
		}
	}

	os_aio_simulated_wake_handler_threads();

	/* Flush pages from the end of the LRU list if necessary */
	buf_flush_free_margin();

#ifdef UNIV_DEBUG
	if (buf_debug_prints) {
		fprintf(stderr,
			"Ibuf merge read-ahead space %lu pages %lu\n",
			(ulong) space_ids[0], (ulong) n_stored);
	}
#endif /* UNIV_DEBUG */
}
예제 #2
0
/********************************************************************//**
Applies linear read-ahead if in the buf_pool the page is a border page of
a linear read-ahead area and all the pages in the area have been accessed.
Does not read any page if the read-ahead mechanism is not activated. Note
that the algorithm looks at the 'natural' adjacent successor and
predecessor of the page, which on the leaf level of a B-tree are the next
and previous page in the chain of leaves. To know these, the page specified
in (space, offset) must already be present in the buf_pool. Thus, the
natural way to use this function is to call it when a page in the buf_pool
is accessed the first time, calling this function just after it has been
bufferfixed.
NOTE 1: as this function looks at the natural predecessor and successor
fields on the page, what happens, if these are not initialized to any
sensible value? No problem, before applying read-ahead we check that the
area to read is within the span of the space, if not, read-ahead is not
applied. An uninitialized value may result in a useless read operation, but
only very improbably.
NOTE 2: the calling thread may own latches on pages: to avoid deadlocks this
function must be written such that it cannot end up waiting for these
latches!
NOTE 3: the calling thread must want access to the page given: this rule is
set to prevent unintended read-aheads performed by ibuf routines, a situation
which could result in a deadlock if the OS does not support asynchronous io.
@return	number of page read requests issued */
UNIV_INTERN
ulint
buf_read_ahead_linear(
/*==================*/
	ulint	space,	/*!< in: space id */
	ulint	zip_size,/*!< in: compressed page size in bytes, or 0 */
	ulint	offset)	/*!< in: page number of a page; NOTE: the current thread
			must want access to this page (see NOTE 3 above) */
{
	buf_pool_t*	buf_pool = buf_pool_get(space, offset);
	ib_int64_t	tablespace_version;
	buf_page_t*	bpage;
	buf_frame_t*	frame;
	buf_page_t*	pred_bpage	= NULL;
	ulint		pred_offset;
	ulint		succ_offset;
	ulint		count;
	int		asc_or_desc;
	ulint		new_offset;
	ulint		fail_count;
	ulint		ibuf_mode;
	ulint		low, high;
	ulint		err;
	ulint		i;
	const ulint	buf_read_ahead_linear_area
		= BUF_READ_AHEAD_LINEAR_AREA(buf_pool);
	ulint		threshold;

	if (UNIV_UNLIKELY(srv_startup_is_before_trx_rollback_phase)) {
		/* No read-ahead to avoid thread deadlocks */
		return(0);
	}

	low  = (offset / buf_read_ahead_linear_area)
		* buf_read_ahead_linear_area;
	high = (offset / buf_read_ahead_linear_area + 1)
		* buf_read_ahead_linear_area;

	if ((offset != low) && (offset != high - 1)) {
		/* This is not a border page of the area: return */

		return(0);
	}

	if (ibuf_bitmap_page(zip_size, offset)
	    || trx_sys_hdr_page(space, offset)) {

		/* If it is an ibuf bitmap page or trx sys hdr, we do
		no read-ahead, as that could break the ibuf page access
		order */

		return(0);
	}

	/* Remember the tablespace version before we ask te tablespace size
	below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
	do not try to read outside the bounds of the tablespace! */

	tablespace_version = fil_space_get_version(space);

	buf_pool_mutex_enter(buf_pool);

	if (high > fil_space_get_size(space)) {
		buf_pool_mutex_exit(buf_pool);
		/* The area is not whole, return */

		return(0);
	}

	if (buf_pool->n_pend_reads
	    > buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
		buf_pool_mutex_exit(buf_pool);

		return(0);
	}

	/* Check that almost all pages in the area have been accessed; if
	offset == low, the accesses must be in a descending order, otherwise,
	in an ascending order. */

	asc_or_desc = 1;

	if (offset == low) {
		asc_or_desc = -1;
	}

	/* How many out of order accessed pages can we ignore
	when working out the access pattern for linear readahead */
	threshold = ut_min((64 - srv_read_ahead_threshold),
			   BUF_READ_AHEAD_AREA(buf_pool));

	fail_count = 0;

	for (i = low; i < high; i++) {
		bpage = buf_page_hash_get(buf_pool, space, i);

		if (bpage == NULL || !buf_page_is_accessed(bpage)) {
			/* Not accessed */
			fail_count++;

		} else if (pred_bpage) {
			/* Note that buf_page_is_accessed() returns
			the time of the first access.  If some blocks
			of the extent existed in the buffer pool at
			the time of a linear access pattern, the first
			access times may be nonmonotonic, even though
			the latest access times were linear.  The
			threshold (srv_read_ahead_factor) should help
			a little against this. */
			int res = ut_ulint_cmp(
				buf_page_is_accessed(bpage),
				buf_page_is_accessed(pred_bpage));
			/* Accesses not in the right order */
			if (res != 0 && res != asc_or_desc) {
				fail_count++;
			}
		}

		if (fail_count > threshold) {
			/* Too many failures: return */
			buf_pool_mutex_exit(buf_pool);
			return(0);
		}

		if (bpage && buf_page_is_accessed(bpage)) {
			pred_bpage = bpage;
		}
	}

	/* If we got this far, we know that enough pages in the area have
	been accessed in the right order: linear read-ahead can be sensible */

	bpage = buf_page_hash_get(buf_pool, space, offset);

	if (bpage == NULL) {
		buf_pool_mutex_exit(buf_pool);

		return(0);
	}

	switch (buf_page_get_state(bpage)) {
	case BUF_BLOCK_ZIP_PAGE:
		frame = bpage->zip.data;
		break;
	case BUF_BLOCK_FILE_PAGE:
		frame = ((buf_block_t*) bpage)->frame;
		break;
	default:
		ut_error;
		break;
	}

	/* Read the natural predecessor and successor page addresses from
	the page; NOTE that because the calling thread may have an x-latch
	on the page, we do not acquire an s-latch on the page, this is to
	prevent deadlocks. Even if we read values which are nonsense, the
	algorithm will work. */

	pred_offset = fil_page_get_prev(frame);
	succ_offset = fil_page_get_next(frame);

	buf_pool_mutex_exit(buf_pool);

	if ((offset == low) && (succ_offset == offset + 1)) {

		/* This is ok, we can continue */
		new_offset = pred_offset;

	} else if ((offset == high - 1) && (pred_offset == offset - 1)) {

		/* This is ok, we can continue */
		new_offset = succ_offset;
	} else {
		/* Successor or predecessor not in the right order */

		return(0);
	}

	low  = (new_offset / buf_read_ahead_linear_area)
		* buf_read_ahead_linear_area;
	high = (new_offset / buf_read_ahead_linear_area + 1)
		* buf_read_ahead_linear_area;

	if ((new_offset != low) && (new_offset != high - 1)) {
		/* This is not a border page of the area: return */

		return(0);
	}

	if (high > fil_space_get_size(space)) {
		/* The area is not whole, return */

		return(0);
	}

	/* If we got this far, read-ahead can be sensible: do it */

	if (ibuf_inside()) {
		ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
	} else {
		ibuf_mode = BUF_READ_ANY_PAGE;
	}

	count = 0;

	/* Since Windows XP seems to schedule the i/o handler thread
	very eagerly, and consequently it does not wait for the
	full read batch to be posted, we use special heuristics here */

	os_aio_simulated_put_read_threads_to_sleep();

	for (i = low; i < high; i++) {
		/* It is only sensible to do read-ahead in the non-sync
		aio mode: hence FALSE as the first parameter */

		if (!ibuf_bitmap_page(zip_size, i)) {
			count += buf_read_page_low(
				&err, FALSE,
				ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
				space, zip_size, FALSE, tablespace_version, i);
			if (err == DB_TABLESPACE_DELETED) {
				ut_print_timestamp(stderr);
				fprintf(stderr,
					"  InnoDB: Warning: in"
					" linear readahead trying to access\n"
					"InnoDB: tablespace %lu page %lu,\n"
					"InnoDB: but the tablespace does not"
					" exist or is just being dropped.\n",
					(ulong) space, (ulong) i);
			}
		}
	}

	/* In simulated aio we wake the aio handler threads only after
	queuing all aio requests, in native aio the following call does
	nothing: */

	os_aio_simulated_wake_handler_threads();

	/* Flush pages from the end of the LRU list if necessary */
	buf_flush_free_margin(buf_pool);

#ifdef UNIV_DEBUG
	if (buf_debug_prints && (count > 0)) {
		fprintf(stderr,
			"LINEAR read-ahead space %lu offset %lu pages %lu\n",
			(ulong) space, (ulong) offset, (ulong) count);
	}
#endif /* UNIV_DEBUG */

	/* Read ahead is considered one I/O operation for the purpose of
	LRU policy decision. */
	buf_LRU_stat_inc_io();

	buf_pool->stat.n_ra_pages_read += count;
	return(count);
}
예제 #3
0
ulint
buf_read_ahead_linear(
/*==================*/
			/* out: number of page read requests issued */
	ulint	space,	/* in: space id */
	ulint	offset)	/* in: page number of a page; NOTE: the current thread
			must want access to this page (see NOTE 3 above) */
{
	ib_longlong	tablespace_version;
	buf_block_t*	block;
	buf_frame_t*	frame;
	buf_block_t*	pred_block	= NULL;
	ulint		pred_offset;
	ulint		succ_offset;
	ulint		count;
	int		asc_or_desc;
	ulint		new_offset;
	ulint		fail_count;
	ulint		ibuf_mode;
	ulint		low, high;
	ulint		err;
	ulint		i;

	if (srv_startup_is_before_trx_rollback_phase) {
		/* No read-ahead to avoid thread deadlocks */
		return(0);
	}

	if (ibuf_bitmap_page(offset) || trx_sys_hdr_page(space, offset)) {

		/* If it is an ibuf bitmap page or trx sys hdr, we do
		no read-ahead, as that could break the ibuf page access
		order */

		return(0);
	}

	low  = (offset / BUF_READ_AHEAD_LINEAR_AREA)
		* BUF_READ_AHEAD_LINEAR_AREA;
	high = (offset / BUF_READ_AHEAD_LINEAR_AREA + 1)
		* BUF_READ_AHEAD_LINEAR_AREA;

	if ((offset != low) && (offset != high - 1)) {
		/* This is not a border page of the area: return */

		return(0);
	}

	/* Remember the tablespace version before we ask te tablespace size
	below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
	do not try to read outside the bounds of the tablespace! */

	tablespace_version = fil_space_get_version(space);

	mutex_enter(&(buf_pool->mutex));

	if (high > fil_space_get_size(space)) {
		mutex_exit(&(buf_pool->mutex));
		/* The area is not whole, return */

		return(0);
	}

	if (buf_pool->n_pend_reads
	    > buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
		mutex_exit(&(buf_pool->mutex));

		return(0);
	}

	/* Check that almost all pages in the area have been accessed; if
	offset == low, the accesses must be in a descending order, otherwise,
	in an ascending order. */

	asc_or_desc = 1;

	if (offset == low) {
		asc_or_desc = -1;
	}

	fail_count = 0;

	for (i = low; i < high; i++) {
		block = buf_page_hash_get(space, i);

		if ((block == NULL) || !block->accessed) {
			/* Not accessed */
			fail_count++;

		} else if (pred_block
			   && (ut_ulint_cmp(block->LRU_position,
					    pred_block->LRU_position)
			       != asc_or_desc)) {
			/* Accesses not in the right order */

			fail_count++;
			pred_block = block;
		}
	}

	if (fail_count > BUF_READ_AHEAD_LINEAR_AREA
	    - BUF_READ_AHEAD_LINEAR_THRESHOLD) {
		/* Too many failures: return */

		mutex_exit(&(buf_pool->mutex));

		return(0);
	}

	/* If we got this far, we know that enough pages in the area have
	been accessed in the right order: linear read-ahead can be sensible */

	block = buf_page_hash_get(space, offset);

	if (block == NULL) {
		mutex_exit(&(buf_pool->mutex));

		return(0);
	}

	frame = block->frame;

	/* Read the natural predecessor and successor page addresses from
	the page; NOTE that because the calling thread may have an x-latch
	on the page, we do not acquire an s-latch on the page, this is to
	prevent deadlocks. Even if we read values which are nonsense, the
	algorithm will work. */

	pred_offset = fil_page_get_prev(frame);
	succ_offset = fil_page_get_next(frame);

	mutex_exit(&(buf_pool->mutex));

	if ((offset == low) && (succ_offset == offset + 1)) {

		/* This is ok, we can continue */
		new_offset = pred_offset;

	} else if ((offset == high - 1) && (pred_offset == offset - 1)) {

		/* This is ok, we can continue */
		new_offset = succ_offset;
	} else {
		/* Successor or predecessor not in the right order */

		return(0);
	}

	low  = (new_offset / BUF_READ_AHEAD_LINEAR_AREA)
		* BUF_READ_AHEAD_LINEAR_AREA;
	high = (new_offset / BUF_READ_AHEAD_LINEAR_AREA + 1)
		* BUF_READ_AHEAD_LINEAR_AREA;

	if ((new_offset != low) && (new_offset != high - 1)) {
		/* This is not a border page of the area: return */

		return(0);
	}

	if (high > fil_space_get_size(space)) {
		/* The area is not whole, return */

		return(0);
	}

	/* If we got this far, read-ahead can be sensible: do it */

	if (ibuf_inside()) {
		ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
	} else {
		ibuf_mode = BUF_READ_ANY_PAGE;
	}

	count = 0;

	/* Since Windows XP seems to schedule the i/o handler thread
	very eagerly, and consequently it does not wait for the
	full read batch to be posted, we use special heuristics here */

	os_aio_simulated_put_read_threads_to_sleep();

	for (i = low; i < high; i++) {
		/* It is only sensible to do read-ahead in the non-sync
		aio mode: hence FALSE as the first parameter */

		if (!ibuf_bitmap_page(i)) {
			count += buf_read_page_low(
				&err, FALSE,
				ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
				space, tablespace_version, i);
			if (err == DB_TABLESPACE_DELETED) {
				ut_print_timestamp(stderr);
				fprintf(stderr,
					"  InnoDB: Warning: in"
					" linear readahead trying to access\n"
					"InnoDB: tablespace %lu page %lu,\n"
					"InnoDB: but the tablespace does not"
					" exist or is just being dropped.\n",
					(ulong) space, (ulong) i);
			}
		}
	}

	/* In simulated aio we wake the aio handler threads only after
	queuing all aio requests, in native aio the following call does
	nothing: */

	os_aio_simulated_wake_handler_threads();

	/* Flush pages from the end of the LRU list if necessary */
	buf_flush_free_margin();

#ifdef UNIV_DEBUG
	if (buf_debug_prints && (count > 0)) {
		fprintf(stderr,
			"LINEAR read-ahead space %lu offset %lu pages %lu\n",
			(ulong) space, (ulong) offset, (ulong) count);
	}
#endif /* UNIV_DEBUG */

	++srv_read_ahead_seq;
	return(count);
}
예제 #4
0
/************************************************************************
Applies a random read-ahead in buf_pool if there are at least a threshold
value of accessed pages from the random read-ahead area. Does not read any
page, not even the one at the position (space, offset), if the read-ahead
mechanism is not activated. NOTE 1: the calling thread may own latches on
pages: to avoid deadlocks this function must be written such that it cannot
end up waiting for these latches! NOTE 2: the calling thread must want
access to the page given: this rule is set to prevent unintended read-aheads
performed by ibuf routines, a situation which could result in a deadlock if
the OS does not support asynchronous i/o. */
static
ulint
buf_read_ahead_random(
/*==================*/
			/* out: number of page read requests issued; NOTE
			that if we read ibuf pages, it may happen that
			the page at the given page number does not get
			read even if we return a value > 0! */
	ulint	space,	/* in: space id */
	ulint	offset)	/* in: page number of a page which the current thread
			wants to access */
{
	ib_longlong	tablespace_version;
	buf_block_t*	block;
	ulint		recent_blocks	= 0;
	ulint		count;
	ulint		LRU_recent_limit;
	ulint		ibuf_mode;
	ulint		low, high;
	ulint		err;
	ulint		i;

	if (srv_startup_is_before_trx_rollback_phase) {
		/* No read-ahead to avoid thread deadlocks */
		return(0);
	}

	if (ibuf_bitmap_page(offset) || trx_sys_hdr_page(space, offset)) {

		/* If it is an ibuf bitmap page or trx sys hdr, we do
		no read-ahead, as that could break the ibuf page access
		order */

		return(0);
	}

	/* Remember the tablespace version before we ask te tablespace size
	below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
	do not try to read outside the bounds of the tablespace! */

	tablespace_version = fil_space_get_version(space);

	low  = (offset / BUF_READ_AHEAD_RANDOM_AREA)
		* BUF_READ_AHEAD_RANDOM_AREA;
	high = (offset / BUF_READ_AHEAD_RANDOM_AREA + 1)
		* BUF_READ_AHEAD_RANDOM_AREA;
	if (high > fil_space_get_size(space)) {

		high = fil_space_get_size(space);
	}

	/* Get the minimum LRU_position field value for an initial segment
	of the LRU list, to determine which blocks have recently been added
	to the start of the list. */

	LRU_recent_limit = buf_LRU_get_recent_limit();

	mutex_enter(&(buf_pool->mutex));

	if (buf_pool->n_pend_reads
	    > buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
		mutex_exit(&(buf_pool->mutex));

		return(0);
	}

	/* Count how many blocks in the area have been recently accessed,
	that is, reside near the start of the LRU list. */

	for (i = low; i < high; i++) {
		block = buf_page_hash_get(space, i);

		if ((block)
		    && (block->LRU_position > LRU_recent_limit)
		    && block->accessed) {

			recent_blocks++;
		}
	}

	mutex_exit(&(buf_pool->mutex));

	if (recent_blocks < BUF_READ_AHEAD_RANDOM_THRESHOLD) {
		/* Do nothing */

		return(0);
	}

	/* Read all the suitable blocks within the area */

	if (ibuf_inside()) {
		ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
	} else {
		ibuf_mode = BUF_READ_ANY_PAGE;
	}

	count = 0;

	for (i = low; i < high; i++) {
		/* It is only sensible to do read-ahead in the non-sync aio
		mode: hence FALSE as the first parameter */

		if (!ibuf_bitmap_page(i)) {
			count += buf_read_page_low(
				&err, FALSE,
				ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
				space, tablespace_version, i);
			if (err == DB_TABLESPACE_DELETED) {
				ut_print_timestamp(stderr);
				fprintf(stderr,
					"  InnoDB: Warning: in random"
					" readahead trying to access\n"
					"InnoDB: tablespace %lu page %lu,\n"
					"InnoDB: but the tablespace does not"
					" exist or is just being dropped.\n",
					(ulong) space, (ulong) i);
			}
		}
	}

	/* In simulated aio we wake the aio handler threads only after
	queuing all aio requests, in native aio the following call does
	nothing: */

	os_aio_simulated_wake_handler_threads();

#ifdef UNIV_DEBUG
	if (buf_debug_prints && (count > 0)) {
		fprintf(stderr,
			"Random read-ahead space %lu offset %lu pages %lu\n",
			(ulong) space, (ulong) offset,
			(ulong) count);
	}
#endif /* UNIV_DEBUG */

	++srv_read_ahead_rnd;
	return(count);
}