Hi, Sergey! On Apr 17, svoj@mariadb.org wrote:

revision-id: 696188fe2f0756a98914df5b95ba302f7e5c55df parent(s): 0520a009c7139c940ab92345054bf0dba7808b11 committer: Sergey Vojtovich branch nick: mariadb timestamp: 2015-04-17 14:30:15 +0400 message:

MDEV-7951 - sql_alloc() takes 0.25% in OLTP RO

sql_alloc() has additional costs compared to direct mem_root allocation: - function call: it is defined in a separate translation unit and can't be inlined - it needs to call pthread_getspecific() to get THD::mem_root

It is called dozens of times implicitely at least by: - List<>::push_back() - List<>::push_front() - new (for Sql_alloc derived classes) - sql_memdup()

Replaced lots of implicit sql_alloc() calls with direct mem_root allocation, passing through THD pointer whenever it is needed.

Number of sql_alloc() calls reduced 345 -> 41 per OLTP RO transaction. pthread_getspecific() overhead dropped 0.76 -> 0.59 sql_alloc() overhed dropped 0.25 -> 0.06

ok to push Regards, Sergei