Provide some statistics about asynchronous IO reads and writes:
- number of pending operations
- number of completion callbacks that are currently being executed
- number of completion callbacks that are currently queued
(due to restriction on number of IO threads)
- total number of IOs finished
- total time to wait for free IO slot
- total number of completions that were queued.
Also revert tpool InnoDB perfschema instrumentation (MDEV-31048)
That instrumentation of cache mutex did not bring any revelation (
the mutex is taken for a couple of instructions), and made it impossible
to use tpool outside of the server (e.g in mariadbimport/dump)
When the constant OS_AIO_N_PENDING_IOS_PER_THREAD is changed from 256 to 1
and the server is run with the minimum parameters
innodb_read_io_threads=1 and innodb_write_io_threads=2, two hangs
were observed.
tpool::cache<T>::put(T*): Ensure that get() in io_slots::acquire()
will be woken up when the cache previously was empty.
buf_pool_t::io_buf_t::reserve(): Schedule a possibly partial doublewrite
batch so that os_aio_wait_until_no_pending_writes() has a chance of
returning. Add a Boolean parameter and pass wait_for_reads=false inside
buf_page_decrypt_after_read(), because those calls will be executed
inside a read completion callback, and therefore
os_aio_wait_until_no_pending_reads() would block indefinitely.
The MDEV-29693 conflict resolution is from Monty, as well as is
a bug fix where ANALYZE TABLE wrongly built histograms for
single-column PRIMARY KEY.
Also includes a fix for safe_malloc error reporting.
Other things:
- Copied main.log_slow from 10.4 to avoid mtr issue
Disabled test:
- spider/bugfix.mdev_27239 because we started to get
+Error 1429 Unable to connect to foreign data source: localhost
-Error 1158 Got an error reading communication packets
- main.delayed
- Bug#54332 Deadlock with two connections doing LOCK TABLE+INSERT DELAYED
This part is disabled for now as it fails randomly with different
warnings/errors (no corruption).
Add threadpool functionality to restrict concurrency during "batch"
periods (where tasks are added in rapid succession).
This will throttle thread creation more agressively than usual, while
keeping performance at least on-par.
One of these cases is bufferpool load, where async read IOs are executed
without any throttling. There can be as much as 650K read IOs for
loading 10GB buffer pool.
Another one is recovery, where "fake read" IOs are executed.
Why there are more threads than we expect?
Worker threads are not be recognized as idle, until they return to the
standby list, and to return to that list, they need to acquire
mutex currently held in the submit_task(). In those cases, submit_task()
has no worker to wake, and would create threads until default concurrency
level (2*ncpus) is satisfied. Only after that throttling would happen.
tpool::cache::m_mtx: Add PERFORMANCE_SCHEMA instrumentation
(wait/synch/mutex/innodb/tpool_cache_mutex). This covers the
InnoDB read_slots and write_slots for asynchronous data page I/O.
Fixes the following error when building with gcc 13:
"tpool/aio_liburing.cc:64:18: error: 'runtime_error' is not a member of 'std'
64 | throw std::runtime_error("aio_uring()");"
The resources like uring in MariaDB aren't intended for spawned
processes so we restrict access using the io_uring_ring_dontfork
liburing library call.
Removed use std::vector's ba push_back(), pop_back() to make it more
obvious that memory in the vectors won't be reallocated.
Also, "borrowed" elements can be debugged a little better now,
they are put into the start of the m_cache vector.
Fix concurrency error - avoid accessing deleted memory, when io_slots is
resized. the deleted memory in this case was vftable pointer in
aiocb::m_internal_task
The fix avoids calling dummy release function, via a flag in task_group.
Fixed tpool timer implementation on POSIX.
Prior to this patch, under some specific rare circumstances (concurrency
related), timer callback execution might be skipped.
Table_cache_instance: Define the structure aligned at
the CPU cache line, and remove a pad[] data member.
Krunal Bauskar reported this to improve performance on ARMv8.
aligned_malloc(): Wrapper for the Microsoft _aligned_malloc()
and the ISO/IEC 9899:2011 <stdlib.h> aligned_alloc().
Note: The parameters are in the Microsoft order (size, alignment),
opposite of aligned_alloc(alignment, size).
Note: The standard defines that size must be an integer multiple
of alignment. It is enforced by AddressSanitizer but not by GNU libc
on Linux.
aligned_free(): Wrapper for the Microsoft _aligned_free() and
the standard free().
HAVE_ALIGNED_ALLOC: A new test. Unfortunately, support for
aligned_alloc() may still be missing on some platforms.
We will fall back to posix_memalign() for those cases.
HAVE_MEMALIGN: Remove, along with any use of the nonstandard memalign().
PFS_ALIGNEMENT (sic): Removed; we will use CPU_LEVEL1_DCACHE_LINESIZE.
PFS_ALIGNED: Defined using the C++11 keyword alignas.
buf_pool_t::page_hash_table::create(),
lock_sys_t::hash_table::create():
lock_sys_t::hash_table::resize(): Pad the allocation size to an
integer multiple of the alignment.
Reviewed by: Vladislav Vaintroub
aio_uring::thread_routine(): Handle -EINTR from io_uring_wait_cqe()
in the same way as aio_linux::getevent_thread_routine() does it:
simply ignore it and invoke the system call again.
Reviewed by: Vladislav Vaintroub
As btrfs showed, a partial read of data in AIO /O_DIRECT circumstances can
really confuse MariaDB.
Filipe Manana (SuSE)[1] showed how database programmers can assume
O_DIRECT is all or nothing.
While a fix was done in the kernel side, we can do better in our code by
requesting that the rest of the block be read/written synchronously if
we do only get a partial read/write.
Per the APIs, a partial read/write can occur before an error, so
reattempting the request will leave the caller with a concrete error to
handle.
[1] https://lore.kernel.org/linux-btrfs/CABVffENfbsC6HjGbskRZGR2NvxbnQi17gAuW65eOM+QRzsr8Bg@mail.gmail.com/T/#mb2738e675e48e0e0778a2e8d1537dec5ec0d3d3a
Also spell synchronously correctly in other files.
