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

revision-id: 3f0b02351a53e0fcaee8554c2c852fb3da8fe7da parent(s): 5d03dd20a4abbfd9777b619dfd51a6927323955a committer: Sergey Vojtovich branch nick: mariadb timestamp: 2015-06-17 18:55:38 +0400 message:

MDEV-7952 - clock_gettime() takes 0.24% in OLTP RO

Initialize abs_timeout when it is about to be used. This saves one my_hrtime() call on hot path (when we acquire MDL lock without waiting).

ok

When filling I_S.PROCESSLIST use THD::start_utime/THD::utime_after_query instead of THD::start_time. This allows us to save 2 clock_gettime() calls.

see below

diff --git a/sql/sql_show.cc b/sql/sql_show.cc index 1e4723d..fa3161a 100644 --- a/sql/sql_show.cc +++ b/sql/sql_show.cc @@ -2730,7 +2730,7 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond) TABLE *table= tables->table; CHARSET_INFO *cs= system_charset_info; char *user; - my_hrtime_t unow= my_hrtime(); + ulonglong unow= microsecond_interval_timer(); DBUG_ENTER("fill_schema_processlist");

DEBUG_SYNC(thd,"fill_schema_processlist_after_unow"); @@ -2793,9 +2793,12 @@ int fill_schema_processlist(THD* thd, TABLE_LIST* tables, COND* cond) table->field[4]->store(command_name[tmp->get_command()].str, command_name[tmp->get_command()].length, cs); /* MYSQL_TIME */ - ulonglong start_utime= tmp->start_time * HRTIME_RESOLUTION + tmp->start_time_sec_part; - ulonglong utime= start_utime && start_utime < unow.val - ? unow.val - start_utime : 0; + ulonglong utime= tmp->start_utime; + ulonglong utime_after_query_snapshot= tmp->utime_after_query; + if (utime < utime_after_query_snapshot) + utime= utime_after_query_snapshot; // COM_SLEEP + utime= utime && utime < unow ? unow - utime : 0;

1. Please add an assert here that utime<=unow. It uses microsecond_interval_timer(), which is supposed to be strictly increasing (unlike my_hrtime()). 2. You might need to update mysqld_list_processes() too.

table->field[5]->store(utime / HRTIME_RESOLUTION, TRUE); /* STATE */

Regards, Sergei