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remove an unnecessary (and contended) latch acquisition from dirty page table

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Sears Russell 2011-08-19 22:43:28 +00:00
parent 829a2441e5
commit c79f22a277
2 changed files with 11 additions and 11 deletions
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20
src/stasis/dirtyPageTable.c
View file

@ -4,10 +4,11 @@
* Created on: May 18, 2009
* Author: sears
*/
#include <config.h>
#include <stasis/common.h>
#include <stasis/util/redblack.h>
#include <stasis/util/multiset.h>
#include <stasis/util/latches.h>
#include <stasis/flags.h>
#include <stasis/dirtyPageTable.h>
#include <stasis/page.h>
@ -36,7 +37,7 @@ struct stasis_dirty_page_table_t {
struct rbtree * tableByPage;
struct rbtree * tableByLsnAndPage;
stasis_buffer_manager_t * bufferManager;
pageid_t count;
uint32_t count; // NOTE: this is 32 bit so that it is cheap to atomically manipulate it on 32 bit intels.
pthread_mutex_t mutex;
pthread_cond_t flushDone;
int flushing;
@ -60,7 +61,7 @@ void stasis_dirty_page_table_set_dirty(stasis_dirty_page_table_t * dirtyPages, P
e->lsn = p->LSN;
ret = rbsearch(e, dirtyPages->tableByLsnAndPage);
assert(ret == e); // otherwise, the entry was already in the table.
dirtyPages->count++;
FETCH_AND_ADD(&dirtyPages->count,1);
}
pthread_mutex_unlock(&dirtyPages->mutex);
#ifdef SANITY_CHECKS
@ -100,7 +101,8 @@ void stasis_dirty_page_table_set_clean(stasis_dirty_page_table_t * dirtyPages, P
pthread_cond_broadcast( &dirtyPages->writebackCond );
}
dirtyPages->count--;
//dirtyPages->count--;
FETCH_AND_ADD(&dirtyPages->count, -1);
}
pthread_mutex_unlock(&dirtyPages->mutex);
}
@ -129,11 +131,7 @@ lsn_t stasis_dirty_page_table_minRecLSN(stasis_dirty_page_table_t * dirtyPages)
}
pageid_t stasis_dirty_page_table_dirty_count(stasis_dirty_page_table_t * dirtyPages) {
pthread_mutex_lock(&dirtyPages->mutex);
pageid_t ret = dirtyPages->count;
assert(dirtyPages->count >= 0);
pthread_mutex_unlock(&dirtyPages->mutex);
return ret;
return ATOMIC_READ_32(&dirtyPages->mutex, &dirtyPages->count);
}
int stasis_dirty_page_table_flush_with_target(stasis_dirty_page_table_t * dirtyPages, lsn_t targetLsn ) {
@ -188,7 +186,7 @@ int stasis_dirty_page_table_flush_with_target(stasis_dirty_page_table_t * dirtyP
if (!all_flushed &&
targetLsn < LSN_T_MAX &&
dirtyPages->count > 0 &&
ATOMIC_READ_32(0, &dirtyPages->count) > 0 &&
e && targetLsn > e->lsn ) {
struct timespec ts;
struct timeval tv;
@ -255,7 +253,7 @@ int stasis_dirty_page_table_get_flush_candidates(stasis_dirty_page_table_t * dir
dummy.p = start;
for(const dpt_entry *e = rblookup(RB_LUGTEQ, &dummy, dirtyPages->tableByPage);
e && (stop == 0 || e->p < stop) && n < count;
e && (stop == 0 || e->p < stop) && n < ATOMIC_READ_32(0, &count);
e = rblookup(RB_LUGREAT, e, dirtyPages->tableByPage)) {
if(n == 0 || range_ends[b] != e->p) {
b++;

2
stasis/util/latches.h
View file

@ -120,6 +120,8 @@ void __profile_deletelock (rwl *lock);
#define ATOMIC_READ_64(mutex,_a) *_a
#define ATOMIC_WRITE_64(mutex,_a,_n) do {*_a=_n; } while (0)
#endif
#define ATOMIC_READ_32(mutex,_a) *_a
#define ATOMIC_WRITE_32(mutex,_a,_n) do {*_a=_n; } while (0)
#else
#define CAS(mutex,_a,_o,_n) GCC_ATOMICS_REQUIRED
#define BARRIER() GCC_ATOMICS_REQUIRED