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From:Manuel Arostegui Date:December 7 2012 11:16am
Subject:Handlersockets - mutex_delay contention
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Hello all,

I am testing handlersockets performance in a 5.5.28-29.1-log (Percona)
server.
These are the enabled options:

loose_handlersocket_port = 9998
loose_handlersocket_port_wr = 9999
loose_handlersocket_threads = 48
loose_handlersocket_threads_wr = 1
innodb_spin_wait_delay=0

The machine has 24 (Xeon - 2.00GHz) cores and 64GB RAM. We are using
bonding to make sure the ethernets aren't limiting us here (we get around
90Mbps)

We are able to handler around 500K requests per second using handler socket
plugin. Even though it looks pretty impressive number, it's still not close
to the 750K ones Yoshinori is able to get (
http://yoshinorimatsunobu.blogspot.com.es/2010/10/using-mysql-as-nosql-story-for.html
)
The machine is acting a normal slave in a cluster - receiving normal
traffic from our site (we do this on purpose to see how many requests we
can handle in a normal workload environment)

Obviously we're not expecting to get similar numbers as our tests aren't
the same.
However, doing a bit of profiling to try to determine what's the bottleneck
here we've seen this:

CPU: Intel Architectural Perfmon, speed 2000.26 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit
mask of 0x00 (No unit mask) count 100000
samples  %        image name               symbol name
*2163868  24.2065  mysqld                   mutex_delay*
694540    7.7696  mysqld
build_template(row_prebuilt_struct*, THD*, TABLE*, unsigned int)
626405    7.0074  mysqld                   buf_page_get_gen
607664    6.7978  mysqld                   rec_get_offsets_func
480937    5.3801  mysqld                   cmp_dtuple_rec_with_match
412081    4.6098  mysqld                   btr_cur_search_to_nth_level
365402    4.0876  mysqld                   rec_init_offsets
356064    3.9832  mysqld                   page_cur_search_with_match
310819    3.4770  mysqld                   row_search_for_mysql
274248    3.0679  mysqld                   row_sel_store_mysql_rec
208466    2.3320  mysqld                   my_pthread_fastmutex_lock
185853    2.0791  mysqld                   ha_innobase::index_read(unsigned
char*, unsigned char const*, unsigned int, ha_rkey_function)
182939    2.0465  mysqld                   pfs_mutex_enter_func
154369    1.7269  mysqld                   mtr_memo_slot_release
138558    1.5500  mysqld                   page_check_dir
131622    1.4724  mysqld                   dict_index_copy_types
101162    1.1317  mysqld                   srv_conc_force_exit_innodb
72754     0.8139  mysqld
ha_innobase::change_active_index(unsigned int)
65191     0.7293  mysqld                   my_long10_to_str_8bit
62574     0.7000  mysqld                   btr_pcur_store_position
61900     0.6925  mysqld                   pfs_mutex_exit_func
51889     0.5805  mysqld                   Field_long::pack_length() const
49073     0.5490  mysqld                   srv_conc_enter_innodb
44079     0.4931  mysqld
ha_innobase::init_table_handle_for_HANDLER()
38998     0.4363  mysqld                   Field_tiny::pack_length() const
38868     0.4348  mysqld                   rec_copy_prefix_to_buf
36292     0.4060  mysqld
ha_innobase::innobase_get_index(unsigned int)

That mutex_delay is eating quite a big % of the time.
I have not been able to find what is that related to. Does anyone has a
clue about what's it and if there's a way to improve and overcome it?

Cheers
Manuel.

Thread
Handlersockets - mutex_delay contentionManuel Arostegui7 Dec
  • Re: Handlersockets - mutex_delay contentionManuel Arostegui12 Dec