Created by Alexey Kopytov and last modified
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461. By Alexey Kopytov

Bug #1163439: Unnecessary log_sys->mutex reacquisition in

mtr_log_reserve_and_write() implements the following logic with respect
to log_sys->mutex: if the mini-transaction log contains a single block,
it calls log_reserve_and_write_fast() which acquires log_sys->mutex and
does a "fast" write by appending the new record to the current log
block. If the record does not fit in the current log block,
log_reserve_and_write_fast() releases log_sys->mutex and returns 0, in
which case mtr_log_reserve_and_write() immediately reacquires
log_sys->mutex by calling log_reserve_and_open() and proceeds with the
"slow" write procedure.

It doesn't make sense to release a mutex and reacquire it immediately
and benchmarks show that avoiding this helps to reduce log_sys->mutex
contention in some write-intensive workloads.

Fixed by implementing an alternative to log_reserve_and_open() which
doesn't acquire the mutex (log_open()), removing mutex_exit() from
log_reserve_and_write_fast() when the log record does not fit in the
current block, and using log_open() instead of log_reserve_and_open() in

460. By <email address hidden>

Merge lp:~percona-core/percona-server/release-5.5.29-30.0

459. By <email address hidden>

Merge lp:~akopytov/percona-server/bug1123921

458. By <email address hidden>

Merge lp:~akopytov/percona-server/bug1132350

457. By <email address hidden>

Merge lp:~akopytov/percona-server/bug1132351

456. By <email address hidden>

Empty merge from Percona Server 5.1

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Empty merge from Percona Server 5.1

454. By <email address hidden>

Merge lp:~hrvojem/percona-server/rn-5.5.29-30.0-fix

453. By <email address hidden>

Merge lp:~akopytov/percona-server/bug1123915

452. By <email address hidden>

Merge lp:~akopytov/percona-server/bug1130655

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