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MDEV-22593 - InnoDB: don't take trx_sys.mutex in ReadView::open()

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This was the last abuse of trx_sys.mutex, which is now exclusively
protecting trx_sys.trx_list.

This global acquisition was also potential scalability bottleneck for
oltp_read_write benchmark. Although it didn't expose itself as such due
to larger scalability issues.

Replaced trx_sys.mutex based synchronisation between ReadView creator
thread and purge coordinator thread performing latest view clone with
ReadView::m_mutex.

It also allowed to simplify tri-state view m_state down to boolean
m_open flag.

For performance reasons trx->read_view.close() is left as atomic relaxed
store, so that we don't have to waste resources for otherwise meaningless
mutex acquisition.
This commit is contained in:
Sergey Vojtovich 2020-05-16 01:13:02 +04:00
commit 50b0ce44a2
22 changed files with 265 additions and 320 deletions
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storage/innobase/include/trx0trx.ic
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@ -26,7 +26,7 @@ Created 3/26/1996 Heikki Tuuri
/**********************************************************************//**
Determines if a transaction is in the given state.
The caller must hold trx_sys.mutex, or it must be the thread
The caller must hold trx->mutex, or it must be the thread
that is serving a running transaction.
A running RW transaction must be in trx_sys.rw_trx_hash.
@return TRUE if trx->state == state */