Vladislav Vaintroub wrote:
> Chris, just out of curiosity - is it necessary to have a thread for each
> single task? I might be mistaken, but do not we have a timer or similar for
> that, specifically for periodic tasks?
Yes, we have two timing threads, the Scheduler and the Ticker. The
Scheduler runs tasks at predefined fixed-length intervals. The Ticker
runs them every second.
I initially proposed scheduling updateCardinalities() as a separate
task, like the Scavenger. Kevin suggested that it would be better to
signal updateCardinalities *from* the Scavenger, which is now more
responsive to cache activity.
Cardinality has historically been updated at scavenge time because
that's a naturally good time to do it--both tasks process the entire
record tree.
This approach has three benefits:
1) Scavenger and updateCardinalities() are independent (no syncSysDDL
nonesense).
2) Cardinality will more closely reflect reality because it is invoked
at scavenge time.
3) We retain the intent of the original design.
>
>> -----Original Message-----
>> From: Christopher.Powers@stripped [mailto:Christopher.Powers@stripped]
>> Sent: Thursday, January 15, 2009 2:04 AM
>> To: Kevin Lewis
>> Cc: FalconDev
>> Subject: More on Scavenge vs DDL
>>
>> I decoupled updateCardinalities() from the Scavenger and moved it on to
>> its own thread. Now, each scavenge simply signals it and moves on, no
>> waiting on syncSysDDL.
>>
>> BUT...
>>
>> Database::scavengeRecords() commits pending system transactions, which
>> of course requires a lock syncSysDDL. In the old code, this was done
>> only inside of syncScavenge AND if the scavenge was not 'forced'.
>>
>> Load-based scavenges are the current equivalent of forced scavenges,
>> and
>> also should not commit pending system transactions.
>>
>>
>> // NEW CODE
>>
>> void Database::scavengeRecords(void)
>> {
>> // Commit pending system transactions before proceeding
>>
>> if (systemConnection->transaction)
>> commitSystemTransaction();
>>
>> Sync syncScavenger(&syncScavenge,
>> "Database::scavengeRecords(Scavenge)");
>> syncScavenger.lock(Exclusive)
>> [...]
>>
>>
>> // OLD CODE
>>
>> void Database::retireRecords(bool forced)
>> {
>> int cycle = scavengeCycle;
>>
>> Sync syncScavenger(&syncScavenge, "Database::retireRecords(1)");
>> syncScavenger.lock(Exclusive);
>>
>> if (forced && scavengeCycle > cycle)
>> return;
>>
>> // Commit pending system transactions before proceeding
>>
>> if (!forced && systemConnection->transaction)
>> commitSystemTransaction();
>>
>> --
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>
>
