trx_undo_mem_create_at_db_start(): Invoke recv_sys_t::recover()
instead of buf_page_get_gen(), so that all undo log pages will be
recovered correctly. Failure to do this could prevent InnoDB from
starting up due to "Data structure corruption", or it could
potentially lead to a situation where InnoDB starts up but some
transactions were recovered incorrectly.
recv_sys_t::recover(): Only acquire a buffer-fix on the pages,
not a shared latch. This is adequate protection, because this function
is only being invoked during early startup when no "users" are modifying
buffer pool pages. The only writes are due to server bootstrap
(the data files being created) or crash recovery (changes from
ib_logfile0 being applied).
buf_page_get_gen(): Assert that the function is not invoked while crash
recovery is in progress, and that the special mode BUF_GET_RECOVER is
only invoked during crash recovery or server bootstrap.
All this should really have been part of
commit 850d61736d (MDEV-32042).
in buf_dblwr_t::init_or_load_pages()
- InnoDB fails to set the TRX_SYS_DOUBLEWRITE_SPACE_ID_STORED
flag in transaction system header page while recreating
the undo log tablespaces
buf_dblwr_t::init_or_load_pages(): Tries to reset the
space id and try to write into doublewrite buffer even
when read_only mode is enabled.
In srv_all_undo_tablespaces_open(), InnoDB should try to
open the extra unused undo tablespaces instead of trying to
creating it.
BUF_LRU_MIN_LEN (256) is too high value for low buffer pool(BP) size.
For example, for BP size lower than 80M and 16 K page size, the limit is
more than 5% of total BP and for lowest BP 5M, it is 80% of the BP.
Non-data objects like explicit locks could occupy part of the BP pool
reducing the pages available for LRU. If LRU reaches minimum limit and
if no free pages are available, server would hang with page cleaner not
able to free any more pages.
Fix: To avoid such hang, we adjust the LRU limit lower than the limit
for data objects as checked in buf_LRU_check_size_of_non_data_objects()
i.e. one page less than 5% of BP.
This regression is introduced in 10.6 by following commit.
commit b6a2472489
MDEV-27891: SIGSEGV in InnoDB buffer pool resize
During DML, we check if buffer pool is running out of data pages in
buf_pool_t::running_out. Here is 75% of the buffer pool is occupied by
non-data pages we rollback the current transaction and exit with
ER_LOCK_TABLE_FULL.
The integer division (n_chunks_new / 4) becomes zero whenever the total
number of chunks are < 4 making the check completely ineffective for
such cases. Also the check is inaccurate for larger chunks.
Fix-1: Correct the check in buf_pool_t::running_out.
Fix-2: While waiting for free page, check for
buf_LRU_check_size_of_non_data_objects.
In the merge commit f9807aadef
there were some omissions or errors.
ibuf_remove_free_page(): Return an error if the free list is corrupted
when removing the change buffer on an upgrade. A special 11.0 version of
commit 263932d505 would have been useful.
buf_page_get_gen(): Correctly handle the case that a page was being
concurrently read into the buffer pool and found out to be corrupted.
This was part of commit a4cda66e2d
but had been discarded in the merge.
Because MariaDB Server 11.0 has reached its end of life as of
commit 466ae1cf81 this fix is being applied
to the 11.1 branch.
Issue: When getting a page (buf_page_get_gen) with no latch option
(RW_NO_LATCH), the caller is not expected to follow the B-tree latching
order. However in buf_page_get_low we try to acquire shared page latch
unconditionally to wait for a page that is being loaded by another
thread concurrently. In general it could lead to latch order violation
and deadlock.
Currently it affects the change buffer insert path btr_latch_prev()
which tries to load the previous page out of order with RW_NO_LATCH and
two concurrent inserts into IBUF tree cause deadlock. This problem is
introduced in 10.6 by following commit.
commit 9436c778c3 (MDEV-27058)
Fix: While trying to latch a page with RW_NO_LATCH, always use the
"*lock_try" interface and retry operation on failure after unfixing the
page.
Because the Red Hat Enterprise Linux 8 core repository does not include
libpmem, let us implement the necessary subset ourselves.
pmem_persist(): Implement for 64-bit x86, ARM, POWER, RISC-V, Loongarch
in a way that should be compatible with the https://github.com/pmem/pmdk/
implementation of pmem_persist().
The CMake option WITH_INNODB_PMEM can be used for enabling or disabling
this interface at compile time. By default, it is enabled on all applicable
systems that are covered by our CI system.
Note: libpmem had not been previously enabled for Loongarch in our
Debian packaging. It was enabled for RISC-V, but we will not enable it
by default on RISC-V or Loongarch because we lack CI coverage.
The generated code for x86_64 was reviewed and tested on two
Intel implementations: one that only supports clflush, and
another that supports both clflushopt and clwb.
The generated machine code was also reviewed on https://godbolt.org
using various compiler versions. Godbolt helpfully includes an option
to compile to binary code and display the encoding, which was
useful on POWER.
Reviewed by: Vladislav Vaintroub
In so-called optimistic buffer pool lookups, we must not
dereference a block descriptor before we have made sure that
it is accessible. While buf_pool_t::resize() is running,
block descriptors could become invalid.
The buf::Block_hint class was essentially duplicating
a buf_pool.page_hash lookup that was executed in
buf_page_optimistic_get() anyway. For better locality of
reference, we had better execute that lookup only once.
buf_page_optimistic_fix(): Prepare for buf_page_optimistic_get().
This basically is a simpler version of Buf::Block_hint.
buf_page_optimistic_get(): Assume that buf_page_optimistic_fix()
has been called and the page identifier verified. Should the block
be evicted, the block->modify_clock will be invalidated; we do not
need to check the block->page.id() again. It suffices to check
the block->modify_clock after acquiring the page latch.
btr_pcur_t::old_page_id: Store the expected page identifier
for buf_page_optimistic_fix().
btr_pcur_t::block_when_stored: Remove. This was duplicating
page_cur_t::block.
btr_pcur_optimistic_latch_leaves(): Remove redundant parameters.
First, invoke buf_page_optimistic_fix() on the requested page.
If needed, acquire a latch on the left page. Finally, acquire
a latch on the target page and recheck the block->modify_clock.
If the page had been freed while we were not holding a page latch,
fall back to the slow path. Validate the FIL_PAGE_PREV after
acquiring a latch on the current page. The block->modify_clock
is only being incremented when records are deleted or pages
reorganized or evicted; it does not guard against concurrent
page splits.
Reviewed by: Debarun Banerjee
In commit 24648768b4 (MDEV-30136)
the parameter innodb_flush_method was deprecated, with no direct
replacement for innodb_flush_method=O_DIRECT_NO_FSYNC.
Let us change innodb_doublewrite from Boolean to ENUM that can
be changed while the server is running:
OFF: Assume that writes of innodb_page_size are atomic
ON: Prevent torn writes (the default)
fast: Like ON, but avoid synchronizing writes to data files
The deprecated start-up parameter innodb_flush_method=NO_FSYNC will cause
innodb_doublewrite=ON to be changed to innodb_doublewrite=fast,
which will prevent InnoDB from making any durable writes to data files.
This would normally be done right before the log checkpoint LSN is updated.
Depending on the file systems being used and their configuration,
this may or may not be safe.
The value innodb_doublewrite=fast differs from the previous combination of
innodb_doublewrite=ON and innodb_flush_method=O_DIRECT_NO_FSYNC by always
invoking os_file_flush() on the doublewrite buffer itself
in buf_dblwr_t::flush_buffered_writes_completed(). This should be safer
when there are multiple doublewrite batches between checkpoints.
Typically, once per second, buf_flush_page_cleaner() would write out
up to innodb_io_capacity pages and advance the log checkpoint.
Also typically, innodb_io_capacity>128, which is the size of the
doublewrite buffer in pages. Should os_file_flush_func() not be invoked
between doublewrite batches, writes could be reordered in an unsafe way.
The setting innodb_doublewrite=fast could be safe when the doublewrite
buffer (the first file of the system tablespace) and the data files
reside in the same file system.
This was tested by running "./mtr --rr innodb.alter_kill". On the first
server startup, with innodb_doublewrite=fast, os_file_flush_func()
would only be invoked on the ibdata1 file and possibly ib_logfile0.
On subsequent startups with innodb_doublewrite=OFF, os_file_flush_func()
will be invoked on the individual data files during log_checkpoint().
Note: The setting debug_no_sync (in the code, my_disable_sync) would
disable all durable writes to InnoDB files, which would be much less safe.
IORequest::Type: Introduce special values WRITE_DBL and PUNCH_DBL
for asynchronous writes that are submitted via the doublewrite buffer.
In this way, fil_space_t::use_doublewrite() or buf_dblwr.in_use()
will only be consulted during buf_page_t::flush() and the doublewrite
buffer can be enabled or disabled without any fear of inconsistency.
buf_dblwr_t::block_size: Replaces block_size().
buf_dblwr_t::flush_buffered_writes(): If !in_use() and the doublewrite
buffer is empty, just invoke fil_flush_file_spaces() and return. The
doublewrite buffer could have been disabled while a batch was in
progress.
innodb_init_params(): If innodb_flush_method=O_DIRECT_NO_FSYNC,
set innodb_doublewrite=fast or innodb_doublewrite=fearless.
Thanks to Mark Callaghan for reporting this, and Vladislav Vaintroub
for feedback.
Some fixes related to commit f838b2d799 and
Rows_log_event::do_apply_event() and Update_rows_log_event::do_exec_row()
for system-versioned tables were provided by Nikita Malyavin.
This was required by test versioning.rpl,trx_id,row.
MONITOR_INC_VALUE_CUMULATIVE is a multiline macro, so the second statement
will be executed always, regardless of "if" condition.
These problems first started with
commit b1ab211dee (MDEV-15053).
Thanks to Yury Chaikou from ServiceNow for the report.
By design, InnoDB has always hung when permanently running out of
buffer pool, for example when several threads are waiting to allocate
a block, and all of the buffer pool is buffer-fixed by the active threads.
The hang that we are fixing here occurs when the buffer pool is only
temporarily running out and the situation could be rescued by writing out
some dirty pages or evicting some clean pages.
buf_LRU_get_free_block(): Simplify the way how we wait for
the buf_flush_page_cleaner thread. This fixes occasional hangs
of the test encryption.innochecksum that were introduced by
commit a55b951e60 (MDEV-26827).
To play it safe, we use a timed wait when waiting for the
buf_flush_page_cleaner() thread to perform its job. Should that
thread get stuck, we will invoke buf_pool.LRU_warn() in order to
display a message that pages could not be freed, and keep trying
to wake up the buf_flush_page_cleaner() thread.
The INFORMATION_SCHEMA.INNODB_METRICS counters
buffer_LRU_single_flush_failure_count and
buffer_LRU_get_free_waits will be removed.
The latter is represented by buffer_pool_wait_free.
Also removed will be the message
"InnoDB: Difficult to find free blocks in the buffer pool"
because in d34479dc66 we
introduced a more precise message
"InnoDB: Could not free any blocks in the buffer pool"
in the buf_flush_page_cleaner thread.
buf_pool_t::LRU_warn(): Issue the warning message that we could
not free any blocks in the buffer pool. This may also be invoked
by buf_LRU_get_free_block() if buf_flush_page_cleaner() appears
to be stuck.
buf_pool_t::n_flush_dec(): Remove.
buf_pool_t::n_flush_dec_holding_mutex(): Rename to n_flush_dec().
buf_flush_LRU_list_batch(): Increment the eviction counter for blocks
of temporary, discarded or dropped tablespaces.
buf_flush_LRU(): Make static, and remove the constant parameter
evict=false. The only caller will be the buf_flush_page_cleaner()
thread.
IORequest::is_LRU(): Remove. The only case of evicting pages on
write completion will be when we are writing out pages of the
temporary tablespace. Those pages are not in buf_pool.flush_list,
only in buf_pool.LRU.
buf_page_t::flush(): Remove the parameter evict.
buf_page_t::write_complete(): Change the parameter "bool temporary"
to "bool persistent" and add a parameter for an already read state().
Reviewed by: Debarun Banerjee
The log_sys.lsn_lock is a very contended resource with a small
critical section in log_sys.append_prepare(). On many processor
microarchitectures, replacing the system call based log_sys.lsn_lock
with a pure spin lock would fare worse during high concurrency workloads,
wasting a significant amount of CPU cycles in the spin loop.
On other microarchitectures, we would see a significant amount of time
being spent in native_queued_spin_lock_slowpath() in the Linux kernel,
plus context switching between user and kernel address space. This was
pointed out by Steve Shaw from Intel Corporation.
Depending on the workload and the hardware implementation, it may be
useful to use a pure spin lock in log_sys.append_prepare().
We will introduce a parameter. The statement
SET GLOBAL INNODB_LOG_SPIN_WAIT_DELAY=50;
would enable a spin lock that will execute that many MY_RELAX_CPU()
operations (such as the x86 PAUSE instruction) between successive
attempts of acquiring the spin lock. The use of a system call based
log_sys.lsn_lock (which is the default setting) can be enabled by
SET GLOBAL INNODB_LOG_SPIN_WAIT_DELAY=0;
This patch will also introduce #ifdef LOG_LATCH_DEBUG
(part of cmake -DWITH_INNODB_EXTRA_DEBUG=ON) for more accurate
tracking of log_sys.latch ownership and reorganize the fields of
log_sys to improve the locality of reference and to reduce the
chances of false sharing.
When a spin lock is being used, it will be maintained in the
most significant bit of log_sys.buf_free. This is useful, because that is
one of the fields that is covered by the lock. For IA-32 or AMD64, we
implement the spin lock specially via log_t::lsn_lock_bts(), employing the
i386 LOCK BTS instruction. A straightforward std::atomic::fetch_or() would
translate into an inefficient loop around LOCK CMPXCHG.
mtr_t::spin_wait_delay: The value of innodb_log_spin_wait_delay.
mtr_t::finisher: Pointer to the currently used mtr_t::finish_write()
implementation. This allows to avoid introducing conditional branches.
We no longer invoke log_sys.is_pmem() at the mini-transaction level,
but we would do that in log_write_up_to().
mtr_t::finisher_update(): Update finisher when spin_wait_delay is
changed from or to 0 (the spin lock is changed to log_sys.lsn_lock or
vice versa).
Let us skip the recently added test main.mysql-interactive if
an instrumented ncurses library is not available.
In InnoDB, let us work around an uninstrumented libnuma, by
declaring that the objects returned by numa_get_mems_allowed()
are initialized.
buf_flush_page_cleaner(): Remove a loop that had originally been added
in commit 9d1466522e (MDEV-32029) and made
redundant by commit 5b53342a6a (MDEV-32588).
Starting with commit d34479dc66 (MDEV-33053)
this loop would cause a significant performance regression in workloads
where buf_pool.need_LRU_eviction() constantly holds in
buf_flush_page_cleaner().
Thanks to Steve Shaw of Intel for noticing this.
Reviewed by: Debarun Banerjee
Tested by: Matthias Leich
Ever since commit 412ee0330c
or commit a440d6ed3a
InnoDB should generally not abort when failing to open or create files.
In Datafile::open_or_create() we had failed to set the flag
to avoid abort() on failure, but everywhere else we were setting it.
We may still call abort() via os_file_handle_error().
Reviewed by: Vladislav Vaintroub
buf_read_ahead_linear(): If buf_pool.watch_is_sentinel(*bpage),
do not attempt to read the page frame because the pointer would be null
for the elements of buf_pool.watch[].
Hitting this bug requires the use of a non-default value of
innodb_change_buffering.
A mix of path separators looks odd.
InnoDB: Loading buffer pool(s) from C:\xampp\mysql\data/ib_buffer_pool
This was changed in cf552f5886
Both forward slashes and backward slashes work on Windows. We do not
use \\?\ names.
So we improve the consistent look of it so it doesn't look like a bug.
Normalize, in this case, the path separator to \ for making the filename.
Reported thanks to Github user @celestinoxp.
Closes: https://github.com/ApacheFriends/xampp-build/issues/33
Reviewed by: Marko Mäkelä and Vladislav Vaintroub
In commit a55b951e60 (MDEV-26827)
an error was introduced in a rarely executed code path of the
buf_flush_page_cleaner() thread. As a result, the function
buf_flush_LRU() could be invoked while not holding buf_pool.mutex.
Reviewed by: Debarun Banerjee
buf_flush_LRU(): Display a warning if no pages could be evicted and
no writes initiated.
buf_pool_t::need_LRU_eviction(): Renamed from buf_pool_t::ran_out().
Check if the amount of free pages is smaller than innodb_lru_scan_depth
instead of checking if it is 0.
buf_flush_page_cleaner(): For the final LRU flush after a checkpoint
flush, use a "budget" of innodb_io_capacity_max, like we do in the
case when we are not in "furious" checkpoint flushing.
Co-developed by: Debarun Banerjee
Reviewed by: Debarun Banerjee
Tested by: Matthias Leich
- InnoDB fails to find the space id from the page0 of
the tablespace. In that case, InnoDB can use
doublewrite buffer to recover the page0 and write
into the file.
- buf_dblwr_t::init_or_load_pages(): Loads only the pages
which are valid.(page lsn >= checkpoint). To do that,
InnoDB has to open the redo log before system
tablespace, read the latest checkpoint information.
recv_dblwr_t::find_first_page():
1) Iterate the doublewrite buffer pages and find the 0th page
2) Read the tablespace flags, space id from the 0th page.
3) Read the 1st, 2nd and 3rd page from tablespace file and
compare the space id with the space id which is stored
in doublewrite buffer.
4) If it matches then we can write into the file.
5) Return space which matches the pages from the file.
SysTablespace::read_lsn_and_check_flags(): Remove the
retry logic for validating the first page. After
restoring the first page from doublewrite buffer,
assign tablespace flags by reading the first page.
recv_recovery_read_max_checkpoint(): Reads the maximum
checkpoint information from log file
recv_recovery_from_checkpoint_start(): Avoid reading
the checkpoint header information from log file
Datafile::validate_first_page(): Throw error in case
of first page validation fails.
When innodb_undo_log_truncate=ON causes an InnoDB undo tablespace
to be truncated, we must guarantee that the undo tablespace will
be rebuilt atomically: After mtr_t::commit_shrink() has durably
written the mini-transaction that rebuilds the undo tablespace,
we must not write any old pages to the tablespace.
To guarantee this, in trx_purge_truncate_history() we used to
traverse the entire buf_pool.flush_list in order to acquire
exclusive latches on all pages for the undo tablespace that
reside in the buffer pool, so that those pages cannot be written
and will be evicted during mtr_t::commit_shrink(). But, this
traversal may interfere with the page writing activity of
buf_flush_page_cleaner(). It would be better to lazily discard
the old pages of the truncated undo tablespace.
fil_space_t::is_being_truncated, fil_space_t::clear_stopping(): Remove.
fil_space_t::create_lsn: A new field, identifying the LSN of the
latest rebuild of a tablespace.
buf_page_t::flush(), buf_flush_try_neighbors(): Evict pages whose
FIL_PAGE_LSN is below fil_space_t::create_lsn.
mtr_t::commit_shrink(): Update fil_space_t::create_lsn and
fil_space_t::size right before the log is durably written and the
tablespace file is being truncated.
fsp_page_create(), trx_purge_truncate_history(): Simplify the logic.
Reviewed by: Thirunarayanan Balathandayuthapani, Vladislav Lesin
Performance tested by: Axel Schwenke
Correctness tested by: Matthias Leich
buf_flush_page_cleaner(): A continue or break inside DBUG_EXECUTE_IF
actually is a no-op. Use an explicit call to _db_keyword_() to
actually avoid advancing the checkpoint.
buf_flush_list_now_set(): Invoke os_aio_wait_until_no_pending_writes()
to ensure that the page write to the system tablespace is completed.
