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Implement non-blocking alternative to mutexes for read serialisation

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This commit is contained in:
Mark Riddoch
2014-06-10 17:59:49 +01:00
parent f7a177dac8
commit 2963a8448b
7 changed files with 230 additions and 51 deletions
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60
server/core/dcb.c
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@ -84,7 +84,13 @@ static bool dcb_set_state_nomutex(
dcb_state_t* old_state);
static void dcb_call_callback(DCB *dcb, DCB_REASON reason);
DCB* dcb_get_zombies(void)
/**
* Return the pointer to the lsit of zombie DCB's
*
* @return Zombies DCB list
*/
DCB *
dcb_get_zombies(void)
{
return zombies;
}
@ -122,6 +128,9 @@ DCB *rval;
spinlock_init(&rval->delayqlock);
spinlock_init(&rval->authlock);
spinlock_init(&rval->cb_lock);
spinlock_init(&rval->pollinlock);
rval->pollinbusy = 0;
rval->readcheck = 0;
rval->fd = -1;
memset(&rval->stats, 0, sizeof(DCBSTATS)); // Zero the statistics
rval->state = DCB_STATE_ALLOC;
@ -1147,12 +1156,14 @@ DCB *dcb;
dcb_printf(pdcb, "\tQueued write data: %d\n",
gwbuf_length(dcb->writeq));
dcb_printf(pdcb, "\tStatistics:\n");
dcb_printf(pdcb, "\t\tNo. of Reads: %d\n", dcb->stats.n_reads);
dcb_printf(pdcb, "\t\tNo. of Writes: %d\n", dcb->stats.n_writes);
dcb_printf(pdcb, "\t\tNo. of Buffered Writes: %d\n", dcb->stats.n_buffered);
dcb_printf(pdcb, "\t\tNo. of Accepts: %d\n", dcb->stats.n_accepts);
dcb_printf(pdcb, "\t\tNo. of High Water Events: %d\n", dcb->stats.n_high_water);
dcb_printf(pdcb, "\t\tNo. of Low Water Events: %d\n", dcb->stats.n_low_water);
dcb_printf(pdcb, "\t\tNo. of Reads: %d\n", dcb->stats.n_reads);
dcb_printf(pdcb, "\t\tNo. of Writes: %d\n", dcb->stats.n_writes);
dcb_printf(pdcb, "\t\tNo. of Buffered Writes: %d\n", dcb->stats.n_buffered);
dcb_printf(pdcb, "\t\tNo. of Accepts: %d\n", dcb->stats.n_accepts);
dcb_printf(pdcb, "\t\tNo. of busy polls: %d\n", dcb->stats.n_busypolls);
dcb_printf(pdcb, "\t\tNo. of read rechecks: %d\n", dcb->stats.n_busypolls);
dcb_printf(pdcb, "\t\tNo. of High Water Events: %d\n", dcb->stats.n_high_water);
dcb_printf(pdcb, "\t\tNo. of Low Water Events: %d\n", dcb->stats.n_low_water);
dcb = dcb->next;
}
spinlock_release(&dcbspin);
@ -1211,6 +1222,8 @@ dprintDCB(DCB *pdcb, DCB *dcb)
dcb->stats.n_buffered);
dcb_printf(pdcb, "\t\tNo. of Accepts: %d\n",
dcb->stats.n_accepts);
dcb_printf(pdcb, "\t\tNo. of busy polls: %d\n", dcb->stats.n_busypolls);
dcb_printf(pdcb, "\t\tNo. of read rechecks: %d\n", dcb->stats.n_busypolls);
dcb_printf(pdcb, "\t\tNo. of High Water Events: %d\n",
dcb->stats.n_high_water);
dcb_printf(pdcb, "\t\tNo. of Low Water Events: %d\n",
@ -1711,3 +1724,36 @@ int rval = 0;
return rval;
}
/**
* Called by the EPOLLIN event. Take care of calling the protocol
* read entry point and managing multiple threads copeting for the DCB
* without blocking those threads.
*
* @param dcb The DCB that has data available
*/
void
dcb_pollin(DCB *dcb)
{
spinlock_acquire(&dcb->pollinlock);
if (dcb->pollinbusy == 0)
{
dcb->pollinbusy = 1;
do {
if (dcb->readcheck)
dcb->stats.n_readrechecks++;
dcb->readcheck = 0;
spinlock_release(&dcb->pollinlock);
dcb->func.read(dcb);
spinlock_acquire(&dcb->pollinlock);
} while (dcb->readcheck);
dcb->pollinbusy = 0;
}
else
{
dcb->stats.n_busypolls++;
dcb->readcheck = 1;
}
spinlock_release(&dcb->pollinlock);
}