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MDEV-10296 - Multi-instance table cache

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Table cache instances autosizing.
This commit is contained in:
Sergey Vojtovich
2016-09-08 16:01:28 +04:00
parent 7e9ac7b8ac
commit 8613633f26
6 changed files with 85 additions and 15 deletions
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4
mysql-test/r/mysqld--help.result
View File

@@ -1092,7 +1092,7 @@ The following options may be given as the first argument:
--table-open-cache=#
The number of cached open tables
--table-open-cache-instances=#
The number of table cache instances
Maximum number of table cache instances
--tc-heuristic-recover=name
Decision to use in heuristic recover process. One of: OFF,
COMMIT, ROLLBACK
@@ -1459,7 +1459,7 @@ sysdate-is-now FALSE
table-cache 431
table-definition-cache 400
table-open-cache 431
table-open-cache-instances 1
table-open-cache-instances 8
tc-heuristic-recover OFF
thread-cache-size 151
thread-pool-idle-timeout 60

6
mysql-test/suite/sys_vars/r/sysvars_server_embedded.result
View File

@@ -3889,12 +3889,12 @@ READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME TABLE_OPEN_CACHE_INSTANCES
SESSION_VALUE NULL
GLOBAL_VALUE 1
GLOBAL_VALUE 8
GLOBAL_VALUE_ORIGIN COMPILE-TIME
DEFAULT_VALUE 1
DEFAULT_VALUE 8
VARIABLE_SCOPE GLOBAL
VARIABLE_TYPE BIGINT UNSIGNED
VARIABLE_COMMENT The number of table cache instances
VARIABLE_COMMENT Maximum number of table cache instances
NUMERIC_MIN_VALUE 1
NUMERIC_MAX_VALUE 64
NUMERIC_BLOCK_SIZE 1

6
mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
View File

@@ -4659,12 +4659,12 @@ READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME TABLE_OPEN_CACHE_INSTANCES
SESSION_VALUE NULL
GLOBAL_VALUE 1
GLOBAL_VALUE 8
GLOBAL_VALUE_ORIGIN COMPILE-TIME
DEFAULT_VALUE 1
DEFAULT_VALUE 8
VARIABLE_SCOPE GLOBAL
VARIABLE_TYPE BIGINT UNSIGNED
VARIABLE_COMMENT The number of table cache instances
VARIABLE_COMMENT Maximum number of table cache instances
NUMERIC_MIN_VALUE 1
NUMERIC_MAX_VALUE 64
NUMERIC_BLOCK_SIZE 1

4
sql/sys_vars.cc
View File

@@ -3228,9 +3228,9 @@ static Sys_var_ulong Sys_table_cache_size(
ON_UPDATE(fix_table_open_cache));
static Sys_var_ulong Sys_table_cache_instances(
"table_open_cache_instances", "The number of table cache instances",
"table_open_cache_instances", "Maximum number of table cache instances",
READ_ONLY GLOBAL_VAR(tc_instances), CMD_LINE(REQUIRED_ARG),
VALID_RANGE(1, 64), DEFAULT(1), BLOCK_SIZE(1));
VALID_RANGE(1, 64), DEFAULT(8), BLOCK_SIZE(1));
static Sys_var_ulong Sys_thread_cache_size(
"thread_cache_size",

1
sql/table.h
View File

@@ -1027,6 +1027,7 @@ private:
public:
uint32 instance; /** Table cache instance this TABLE is belonging to */
THD *in_use; /* Which thread uses this */
Field **field; /* Pointer to fields */

79
sql/table_cache.cc
View File

@@ -56,6 +56,8 @@
ulong tdc_size; /**< Table definition cache threshold for LRU eviction. */
ulong tc_size; /**< Table cache threshold for LRU eviction. */
ulong tc_instances;
static uint32 tc_active_instances= 1;
static uint32 tc_contention_warning_reported;
/** Data collections. */
static LF_HASH tdc_hash; /**< Collection of TABLE_SHARE objects. */
@@ -127,10 +129,12 @@ struct Table_cache_instance
I_P_List_null_counter, I_P_List_fast_push_back<TABLE> >
free_tables;
ulong records;
uint mutex_waits;
uint mutex_nowaits;
/** Avoid false sharing between instances */
char pad[CPU_LEVEL1_DCACHE_LINESIZE];
Table_cache_instance(): records(0)
Table_cache_instance(): records(0), mutex_waits(0), mutex_nowaits(0)
{
mysql_mutex_init(key_LOCK_table_cache, &LOCK_table_cache,
MY_MUTEX_INIT_FAST);
@@ -142,6 +146,68 @@ struct Table_cache_instance
DBUG_ASSERT(free_tables.is_empty());
DBUG_ASSERT(records == 0);
}
/**
Lock table cache mutex and check contention.
Instance is considered contested if more than 20% of mutex acquisiotions
can't be served immediately. Up to 100 000 probes may be performed to avoid
instance activation on short sporadic peaks. 100 000 is estimated maximum
number of queries one instance can serve in one second.
These numbers work well on a 2 socket / 20 core / 40 threads Intel Broadwell
system, that is expected number of instances is activated within reasonable
warmup time. It may have to be adjusted for other systems.
Only TABLE object acquistion is instrumented. We intentionally avoid this
overhead on TABLE object release. All other table cache mutex acquistions
are considered out of hot path and are not instrumented either.
*/
void lock_and_check_contention(uint32 n_instances, uint32 instance)
{
if (mysql_mutex_trylock(&LOCK_table_cache))
{
mysql_mutex_lock(&LOCK_table_cache);
if (++mutex_waits == 20000)
{
if (n_instances < tc_instances)
{
if (my_atomic_cas32_weak_explicit(&tc_active_instances, &n_instances,
n_instances + 1,
MY_MEMORY_ORDER_RELAXED,
MY_MEMORY_ORDER_RELAXED))
{
sql_print_information("Detected table cache mutex contention at instance %d: "
"%d%% waits. Additional table cache instance "
"activated. Number of instances after "
"activation: %d.",
instance + 1,
mutex_waits * 100 / (mutex_nowaits + mutex_waits),
n_instances + 1);
}
}
else if (!my_atomic_fas32_explicit(&tc_contention_warning_reported, 1,
MY_MEMORY_ORDER_RELAXED))
{
sql_print_warning("Detected table cache mutex contention at instance %d: "
"%d%% waits. Additional table cache instance "
"cannot be activated: consider raising "
"table_open_cache_instances. Number of active "
"instances: %d.",
instance + 1,
mutex_waits * 100 / (mutex_nowaits + mutex_waits),
n_instances);
}
mutex_waits= 0;
mutex_nowaits= 0;
}
}
else if (++mutex_nowaits == 80000)
{
mutex_waits= 0;
mutex_nowaits= 0;
}
}
};
@@ -287,11 +353,12 @@ void tc_purge(bool mark_flushed)
void tc_add_table(THD *thd, TABLE *table)
{
ulong i= thd->thread_id % tc_instances;
uint32 i= thd->thread_id % my_atomic_load32_explicit(&tc_active_instances, MY_MEMORY_ORDER_RELAXED);
TABLE *LRU_table= 0;
TDC_element *element= table->s->tdc;
DBUG_ASSERT(table->in_use == thd);
table->instance= i;
mysql_mutex_lock(&element->LOCK_table_share);
/* Wait for MDL deadlock detector to complete traversing tdc.all_tables. */
while (element->all_tables_refs)
@@ -327,10 +394,12 @@ void tc_add_table(THD *thd, TABLE *table)
static TABLE *tc_acquire_table(THD *thd, TDC_element *element)
{
ulong i= thd->thread_id % tc_instances;
uint32 n_instances=
my_atomic_load32_explicit(&tc_active_instances, MY_MEMORY_ORDER_RELAXED);
uint32 i= thd->thread_id % n_instances;
TABLE *table;
mysql_mutex_lock(&tc[i].LOCK_table_cache);
tc[i].lock_and_check_contention(n_instances, i);
table= element->free_tables[i].list.pop_front();
if (table)
{
@@ -375,7 +444,7 @@ static TABLE *tc_acquire_table(THD *thd, TDC_element *element)
void tc_release_table(TABLE *table)
{
ulong i= table->in_use->thread_id % tc_instances;
uint32 i= table->instance;
DBUG_ASSERT(table->in_use);
DBUG_ASSERT(table->file);