Re: Reducing ClogControlLock contention

On 08/31/2015 07:34 AM, Amit Kapila wrote:
> I have updated the patch (attached with mail) to show
> you what I have in mind.
>

I havn't been able to get a successful run with _v5 using pgbench.

TransactionIdSetStatusBit assumes an exclusive lock on CLogControlLock
when called, but that part is removed from TransactionIdSetPageStatus now.

I tried an

if (!LWLockHeldByMe(CLogControlLock))
{
LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
mode = LW_EXCLUSIVE;
}

approach, but didn't get further. Plus that probably isn't the best way,
since we will traverse all LWLock's, and we need to account for cases w/
and w/o sub-transactions, e.g. multiple calls to
TransactionIdSetStatusBit within the CLogControlLock exclusive boundary.

Best regards,
Jesper