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MDEV 6766 #8

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ca33814
Include user variable to query cache timeout reading/writing
Sep 23, 2014
280ac45
Include concurrency refused counter
Sep 23, 2014
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1 change: 1 addition & 0 deletions sql/mysqld.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -8212,6 +8212,7 @@ SHOW_VAR status_vars[]= {
{"Qcache_inserts", (char*) &query_cache.inserts, SHOW_LONG},
{"Qcache_lowmem_prunes", (char*) &query_cache.lowmem_prunes, SHOW_LONG},
{"Qcache_not_cached", (char*) &query_cache.refused, SHOW_LONG},
{"Qcache_concurrency_refused", (char*) &query_cache.concurrency_refused, SHOW_LONG},
{"Qcache_queries_in_cache", (char*) &query_cache.queries_in_cache, SHOW_LONG_NOFLUSH},
{"Qcache_total_blocks", (char*) &query_cache.total_blocks, SHOW_LONG_NOFLUSH},
#endif /*HAVE_QUERY_CACHE*/
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36 changes: 29 additions & 7 deletions sql/sql_cache.cc
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Expand Up @@ -586,7 +586,7 @@ void inline fix_local_query_cache_mode(THD *thd)
effect by another thread. This enables a quick path in execution to skip waits
when the outcome is known.

@param mode TIMEOUT the lock can abort because of a timeout
@param mode TIMEOUT_WRITE/TIMEOUT_READ the lock can abort because of a timeout
TRY the lock can abort because it is locked now
WAIT wait for lock (default)

Expand Down Expand Up @@ -643,10 +643,29 @@ bool Query_cache::try_lock(THD *thd, Cache_try_lock_mode mode)
{
mysql_cond_wait(&COND_cache_status_changed, &structure_guard_mutex);
}
else if (mode == TIMEOUT)
else if (mode == TIMEOUT_READ || mode == TIMEOUT_WRITE)
{
struct timespec waittime;
set_timespec_nsec(waittime,(ulong)(50000000L)); /* Wait for 50 msec */
if(mode == TIMEOUT_WRITE){
if(thd->variables.query_cache_write_timeout<=0)
/* Default: wait for 50 msec (nano time value=> 50.000.000ns = 50ms) */
thd->variables.query_cache_write_timeout=50000000L;
if(thd->variables.query_cache_write_timeout>1000000000L;
/* Max value of 1s (1.000.000.000) */
thd->variables.query_cache_write_timeout=1000000000L;

set_timespec_nsec(waittime,(ulong)(thd->variables.query_cache_write_timeout));
}
else
{
if(thd->variables.query_cache_read_timeout<=0)
/* Default: wait for 50 msec (nano time value=> 50.000.000ns = 50ms) */
thd->variables.query_cache_read_timeout=50000000L;
if(thd->variables.query_cache_read_timeout>1000000000L;
/* Max value of 1s (1.000.000.000) */
thd->variables.query_cache_read_timeout=1000000000L;
set_timespec_nsec(waittime,(ulong)(thd->variables.query_cache_read_timeout));
}
int res= mysql_cond_timedwait(&COND_cache_status_changed,
&structure_guard_mutex, &waittime);
if (res == ETIMEDOUT)
Expand Down Expand Up @@ -1275,6 +1294,7 @@ Query_cache::Query_cache(ulong query_cache_limit_arg,
query_cache_limit(query_cache_limit_arg),
queries_in_cache(0), hits(0), inserts(0), refused(0),
total_blocks(0), lowmem_prunes(0),
concurrency_refused(0),
m_cache_status(OK),
min_allocation_unit(ALIGN_SIZE(min_allocation_unit_arg)),
min_result_data_size(ALIGN_SIZE(min_result_data_size_arg)),
Expand Down Expand Up @@ -1474,10 +1494,10 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
In case the wait time can't be determined there is an upper limit which
causes try_lock() to abort with a time out.

The 'TIMEOUT' parameter indicate that the lock is allowed to timeout
The TIMEOUT_WRITE parameter indicate that the lock is allowed to timeout

*/
if (try_lock(thd, Query_cache::TIMEOUT))
if (try_lock(thd, Query_cache::TIMEOUT_WRITE))
DBUG_VOID_RETURN;
if (query_cache_size == 0)
{
Expand Down Expand Up @@ -1576,6 +1596,8 @@ def_week_frmt: %lu, in_trans: %d, autocommit: %d",
}
else
{
// Concorrency counter
concurrency_refused++;
// Another thread is processing the same query => do nothing
refused++;
unlock();
Expand Down Expand Up @@ -1853,9 +1875,9 @@ Query_cache::send_result_to_client(THD *thd, char *org_sql, uint query_length)
disabled or if a full cache flush is in progress, the attempt to
get the lock is aborted.

The TIMEOUT parameter indicate that the lock is allowed to timeout.
The TIMEOUT_READ parameter indicate that the lock is allowed to timeout.
*/
if (try_lock(thd, Query_cache::TIMEOUT))
if (try_lock(thd, Query_cache::TIMEOUT_READ))
goto err;

if (query_cache_size == 0)
Expand Down
5 changes: 3 additions & 2 deletions sql/sql_cache.h
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Original file line number Diff line number Diff line change
Expand Up @@ -294,7 +294,8 @@ class Query_cache
ulong query_cache_size, query_cache_limit;
/* statistics */
ulong free_memory, queries_in_cache, hits, inserts, refused,
free_memory_blocks, total_blocks, lowmem_prunes;
free_memory_blocks, total_blocks, lowmem_prunes,
concurrency_refused;


private:
Expand Down Expand Up @@ -524,7 +525,7 @@ class Query_cache
static uint filename_2_table_key (char *key, const char *filename,
uint32 *db_langth);

enum Cache_try_lock_mode {WAIT, TIMEOUT, TRY};
enum Cache_try_lock_mode {WAIT, TIMEOUT_WRITE, TIMEOUT_READ, TRY};
bool try_lock(THD *thd, Cache_try_lock_mode mode= WAIT);
void lock(THD *thd);
void lock_and_suspend(void);
Expand Down
2 changes: 2 additions & 0 deletions sql/sql_class.h
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Expand Up @@ -570,6 +570,8 @@ typedef struct system_variables
ulong progress_report_time;
ulong completion_type;
ulong query_cache_type;
ulong query_cache_write_timeout;
ulong query_cache_read_timeout;
ulong tx_isolation;
ulong updatable_views_with_limit;
int max_user_connections;
Expand Down
12 changes: 12 additions & 0 deletions sql/sys_vars.cc
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Expand Up @@ -2539,6 +2539,18 @@ static Sys_var_enum Sys_thread_handling(
);

#ifdef HAVE_QUERY_CACHE
static Sys_var_ulong Sys_query_cache_write_timeout(
"query_cache_write_timeout",
"Timeout in nanoseconds waiting lock in query cache insert, "
"default of 50000000 ns = 50ms",
SESSION_VAR(query_cache_write_timeout), CMD_LINE(REQUIRED_ARG),
VALID_RANGE(0, 1000000000L), DEFAULT(50000000), BLOCK_SIZE(1));
static Sys_var_ulong Sys_query_cache_read_timeout(
"query_cache_read_timeout",
"Timeout in nanoseconds waiting lock in query cache fetch, "
"default of 50000000 ns = 50ms",
SESSION_VAR(query_cache_read_timeout), CMD_LINE(REQUIRED_ARG),
VALID_RANGE(0, 1000000000L), DEFAULT(50000000), BLOCK_SIZE(1));
static bool check_query_cache_size(sys_var *self, THD *thd, set_var *var)
{
if (global_system_variables.query_cache_type == 0 &&
Expand Down